Diagramas de Mollier

Transfair Engineering: Survey about CFC-free Refrigerator Production - Part 4: C o o l in i n g C i r c u it i t C o n n e c t io io n S c h e m e

Accumulator

Designing and Prototyping of Refrigerator and Freezer Cooling Circuits Düsseldorf 10/2010 Walter Dirk Adler Transfair GmbH

Mörsenbroicher Weg 179 D-40470 Düsseldorf Tel.: (++49) 211-638811 Fax.: (++49) 211-638898 E-Mail: [email protected]

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator Refrigerator and Freezer Cooling Circuits. Contents

p. 2

CONTENTS 1. 1.1. 1.2. 1.3.

INTRODUCTION Refrigeration Cycle -Definitions Designing of Refrigerator and Freezer Cooling Circuits Standards and Climate Classes

1.3.1 1.3.2 1.3.3

Refrigerator and Freezer Performance Standards Climate Classes Electrical Safety Standards

1.4.

Refrigeration Capacity

1.5.

Reduction of Thermal Losses

1.4.1 1.4.2 1.5.1 1.5.2

1.5.3

Calculation of Thermal Losses and Freezing Power Measurement of the Cabinet Constant Foam Insulation Thickness Polyurethane Foam Tests Measurement of the Foam Density in Refrigerators and Test Shots Dimensional Stability Verification of Reaction Parameters, Cream Time, String Time, Rise Time Assurance of a Continuous Quality Thermal Bridges Sealing between Door and Cabinet Reduced Space between Food liner and Door liner Design of Door Gasket, Air Tightness Test of Door Gaskets

2. COMPRESSOR 2.1.

Replacements of CFC-12 Compressors

2.2.

Compressor Capacities

2.2.1 2.2.2 2.2.3 2.2.4

Energy Efficiencies, Drop-in Solutions, Reliabilities and Lifetimes Compressor Dimensions and Spaces, Investments and Costs

HP Value Nominal Displacement Refrigeration Capacity Coefficient of Performance

8 8 9 9 9 9 10 10 11 13 13 14 14 14 14 15 15 15 16 16 16

17 17 17 17 18

18 18 18 18

2.3.

Starting Characteristics

Low or High Starting Torque, RSIR, RSCR, CSIR, CSR Start Capacitor, PTC, Relay, High Starting Torque Compressor, Run Capacitor

19 19 19

2.4. 2.5. 2.6. 2.7.

Electrical Diagrams Lifetime Heavy Duty Evaporating Temperature

20 20 21 21

2.8.

Comparison between R134a and R12 Compressors

21 21

2.8.1 2.8.2

2.8.3

2.9.

2.9.1 2.9.2

LBP, MBP, HBP

Pressure-/Enthalpy Diagram of R12 and R134a A Comparison Test made by Danfoss Conclusions (Part 1) A comparison Test made by National Matsushita Reciprocal Compressor Rotary Compressor Conclusions (Part 2): Needed Design Improvements Comparison Tests of R134a, R600a and R12 Compressors from Necchi

Compressor COP Tests Fridge/Freezer Tests using R600a, R290/R600a Mixture, R134a and R12 Compressors Conclusions (Part 3)

Cooling Capacities, Coefficient of Performances, R600a Displacement Increase, Charge Tolerances, R290/R600a Drop-in Solution, Noise, Overall Dimensions

19

21 22 22 23 23 23

24 25 25 25 26 26

26


2.10. 2.11. 2.12. 2.10.

of Compressors, R134a Lubricant, R134a Sludge Formation, For mation, R600a Solubility and Foaming, R600a Flammability, Compressor Costs

27

Energy Optimised Compressors Variable Capacity Compressor Compressor Performance Tests and Test Methods Labelling of Compressors with Flammable Gas (R600a, R290 etc.)

27 28 29 29

3. CONDENSER 3.1.

Static Condensers

3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6

Wire-on-Tube Condensers Tube-on -Finned -Plate Condensers Condenser Constant Condenser Capacity Condenser Transmission Coefficient or U-Value Condenser Surface

3.2

Skin Condenser

3.2.1 3.2.2 3.2.3 3.2.4

Skin Condenser on a Refrigerator or Freezer Cabinets Skin Condenser on a Chest Freezer Relation between Volume, Tube Length, Tube Distance and k-Value Necessary Increase of Insulation of Skin Condenser Refrigerators and Freezers Sheet Cover on Condenser

3.3. 3.4. 3.5.

Anti-Dew Coil Oil Cooling Condenser Fan Cooled Condenser

3.5.1 3.5.2 3.6.

3.6.1 3.6.2 3.6.3.

p. 3

Fin Coil Characteristics Possible Solutions for the Air Ducts

Testing Condensers

Calorimetric Measurement Comparison Test of Condenser Capacities Standards of condenser performance testing and test methods

31 31 31 31 31 31 32 33 33 34 34 35 35 35 36 36 37 37 38 38 38 39 40

4. CAPILLARY TUBE AND HEAT EXCHANGER

42

4.1. 4.2. 4.3.

42 43 44

Capillary Tube Capacity Calculation Capillary Tube Capacity Tests Heat Exchanger

5. EVAPORATOR 5.1.

5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.2.

5.2.1

5.2.2

Evaporator Capacity and k-Value Roll-Bond Evaporators

Suction Accumulation Channel Cross Section Samples Evaporator Types, Sizes and Forms Cold Cabinets Evaporator Surface Screening and Drip Trays Two Temperature Cabinets Connection of Refrigerator and Freezer Evaporators in Series Tube-on-Sheet, TOP or Skin Evaporators

Chest Freezers Evaporators Chest Freezer Pull-Down Test Chest Freezer Evaporator Tube Length Working Process to mount Chest Freezer Evaporators Aluminium Tube Evaporators, Steel Tube Evaporators Cold Cabinet Evaporators Flatted evaporator tube with vertical u-bend

46 46 46 46 47 47 47 48 48 49 49 50 51 51 51 52 52 52 53 53


p. 4

5.2.3

54 54 55 55 55 55 56 56 56 57 58 58 58 59 59 59 59 60 60 61 61 61 61 62 62 63 63 64 64 64 65 65 65

5.2.4

5.2.5

Evaporators for one Door Refrigerator with Freezer Compartment Evaporators for one-Door ** Refrigerator Evaporators for one-Door*** Refrigerator Evaporators of two-Door Refrigerator Evaporator in the Refrigerator Part Tube-on-Sheet-Evaporator: Roll Formed Sheet-on-Tubes Evaporator, Aluminium sheet or foils Working Process to mount Tube-on-Sheet or Skin Evaporators on Refrigerators Surface of Tube-on-Sheet Evaporator Freezer Part inside 2 Door Model, Freezer up to and above 60l Tube-on-Plate Freezer Evaporator, Wire-on-Tube Freezer, Evaporators in Series Skin versus Roll-Bond Evaporators Cost Comparison, Processing and Painting, Aesthetic Aspects, Corrosio n and Service Cross Section

5.3.

Optimisation of Evaporators

5.4.

Sizes of Upright Freezer Evaporators

5.5.

NO FROST Evaporators

5.3.1. 5.3.2. 5.3.3. 5.4.1

Evaporator Channels or Tubes and their Cross Sections Speed of refrigerant and Pressure Drop Measurement Liquid-Gas Separator and Accumulator Pull-Down Test of Upright Freezers

5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.5.6

Surface of Fins and Air Charge Tube Size and Fin Distances Defrosting of No Frost Evaporators Air Ducts in NO Frost Refrigerators Damper Thermostat Tandem System Refrigerant Circuit Scheme, Electrical Scheme

5.6. 5.7.

Fridge ventilator Evaporator Tests

5.7.1 5.7.2 5.7.3

Pressure Drop Tests Measurement of Temperature Distribution in Multi-Evaporator Systems with one Control Pull Down Tests Vertical Freezers, Chest Freezers, Fridge-Freezers and Cabinets with or without Freezer Compartment

6. DRYER/DESICCANT

67

6.1. 6.2.

67 68

Filter Dryer characteristic Refrigerant Dryer Test Standards and Methods

7. REFRIGERANT 7.1.

Thermodynamic Characteristics of Different Refrigerants

7.1.1 7.1.2 7.1.3 7.1.4 7.1.5 7.1.6 7.1.7 7.1.8 7.1.8

Efficiencies (COP-Coefficient of Performance) Volumetric Capacities Pressure Differences Pressure Ratios Suction Pressure Superheat Pressure Enthalpy Diagram (Mollier-h, lg p-Diagram) of R134 Pressure enthalpy diagram (Mollier-h, lg p-Diagram) of R600a Pressure enthalpy diagram (Mollier-h, lg p-Diagram) of a R290/R600a Blend

7.2.

Purity and Cleanness Standards

7.3.

Working with R134a in the Refrigerator Laboratory and in the Production

7.3.1 7.3.2 7.3.3 7.3.4

Cleanness Standards Measurement of Cleanliness and Purity

R134a Refrigerant General Characteristics of R134a, Ester Oil Evacuation Pumps Cleaning Technology for Vacuum Pumps for R134a Polyol Ester Oil or PFPE Oil, Cleaning process R134a Charging

70 70 71 71 72 72 72 73 74 75 76 77 77 77 78 78 78 78 78 78 79


p. 5

7.3.5 7.3.6 7.3.7 7.3.8.

Brazing Leak Detection Working with R134a Circuit Elements Mixed Production during during Transition from R12 R12 to R134a or from R134a to R600a: R600a: Anti-Suck Anti-Suck Valves, Suction Oil Separators or Glass Trap in Vacuum Pump

79 79 80 80

7.4.

Working with R600a in the Refrigerator Laboratory and in the Production

81 81 81 81 81 82 83 83

7.2.1

Flammability and Hazardous Situations Flammability of R600a, Safety Precautions, Hazardous Situations 7.4.2 Handling of Hydrocarbon Refrigerant Handling Precautions, Hydrocarbon Cylinders, Transportation, Storage 7.4.2 Evacuation Pumps 7.4.3 R600a Charging Service Charging Equipment, Hydrocarbon Charging Boards, Charging Liquid into Suction, Safety Approved Production Charging Equipment 7.4.4 Exhaust and Ventilation of the Charging Area 7.4.5 Alarm Board with Gas Sensors 7.4.6 Fire Precautions and Fire Extinguishers 7.4.7 Grounding and Anti-Static Floor 7.4.8 Brazing 7.4.9 Leak Detection Pressure Test, Mass Spectrometric Leak Test 7.4.10 Further Precautions 7.5.

7.5.1 7.5.2 7.5.3 7.5.4

Determination of Refrigerant Filling Quantity

Conversion from R12 to R134a, Conversion from R12 to R600a Refrigerant charging: Liquid or Vapour? Charging Accuracy Charging Methods Charging with Dial-A-Charge Cylinder, Charging by Weight, Charging by Sight Glasses Fine Tuning and Control of Charge Charging for Proper Superheat (Superheat Method) Charging for Proper Sub-cooling (Sub-cooling method)

8. Safety Requirements for Refrigerators - especially with HC-Refrigerant 8.1. 8.2.

Safety Standards for Refrigerators and Freezers Special Safety Requirements for Refrigerators using Hydrocarbon Refrigerant

8.3.

Protected Electrical Components in Hydrocarbon Leak Areas

8.2.1 8.2.2 8.2.3 8.2.4

Flammability and Hazardous situations Sealing of the System Potential Ignition Sources Separation of Ignition Sources from Potential Leaks Standard Defrost Models One Door Models

8.3.1 8.3.2 8.3.3 8.3.4. 8.3.5. 8.3.6 8.3.7 8.3.8 8.3.9 8.3.10 8.3.11 8.3.12

Electric Connections Compressor Relay Compressor Overload Protector Compressor Start and Run Capacitors On-Off Switches and Light Switches Luminaries, Lamp Holders and Fluorescent Lighting Ballast and Starter Thermostat Fan Motor and Blades Defrost Heater and Thermal Fuse (in No Frost Models) Defrost Probe, Temperature Cut-Out and Defrost Timer Control (in No Frost Models) Sealed Box (IP53 or higher) Manufacturer’s test of electric component, conformity declacation and markings

8.4. 8.5.

Labelling of Hydrocarbon Refrigerators Electrical Safety Tests and Controls

8.5.1 8.5.2 8.5.3

Electrical Safety Test of all Household Appliances Pressure Test of Refrigerators Charged with Hydrocarbon Leak Simulation Test of Refrigerators Charged with Hydrocarbon

83 84 85 85 85 85 85 86 86 86 86 87 87 87 88 88 89

91

91 91 92 93 93 94 94 94 94 95 95 95 95 95 95 96 96 96 96 96 97 97 97 98 98 98


p. 6

8.5.4 8.5.5 8.5.6.

99 99 100

Scratch Test of Refrigerators Charged with Hydrocarbon Testing of Standard Electric Components not Reachable by Flammable Refrigerant Testing and control of “n” “n” Protected Electrical Components Used in Hydrocarbon Leak Areas

9. TEMPERATURE CONTROL 9.1.

Capillary Tube Thermostat

101 101 101

9.1.1 9.1.2 9.1.3 9.1.4 9.1.5 9.1.6 9.1.7 9.1.8 9.1.9

Operation Range, Adjustment Range, Switching Differential, Correlation between Adjustment Range and Switching Differential, Tolerances, Adjustment in the Refrigerator Factory and in Service, OFF-Position, Dial Layout Standard Thermostat Thermostat with Auxiliary Switch Thermostat with Heater Contact Thermostat with Signal Contact Thermostat with Semi-Automatic Defrost Push-Button Thermostat with Fast-Freeze Thermostat with Fixed Cut-In Temperature Thermostat with a 3-Way Solenoid Valve Control Thermostat with 2 sensors

9.2. 9.3.

Bimetal Thermostat Electronic Control and Thermocouples

9.4.

Special Controls for NO Frost Models

9.5.

Temperature Control Tests

106 106 106 106

10. FINAL TESTS

108

9.4.1 9.4.2

“Child safe” Switch-off, fuzzy logic for running modes: modes: SuperCool, SuperFrost, DuraFreeze, SuperFrost, Frostmatic, Holiday, LCD display control, No-frost freezer defrost control, 3 rd compartment near 0°C Temperature, ice and water spender control, control of variable compressor speed

Defrost Timers and Defrost Thermostats Damper Thermostats

10.1.

Definitions, Classifications, Designs and Characteristics

10.2.

Refrigerator Tests Room

10.3.

Mechanical Tests

10.4. 10.5. 10.6.

Testing of Storage Temperature Water Vapour Condensation Test Energy Consumption Test

10.7. 10.8. 10.9.

Noise of cooling system Temperature Rise Test Freezing Test and Ice-Making Test

Test Conditions and Periods Percentage Running Time

10.2.1 Thermo-insulated test room Dimensions, Lightening, Supply, Regulation Range Loads and Supply Places, Starting Current Voltage, Ampere and Frequency Supply, Flow Chart 10.2.2 Measurement Equipment Energy Measurement, Power Consumption Measurement Power Measurement, Voltage Measurement, Further Electrical Test Equipment, Control Panel, Connection Panel 10.2.3 Measurement Ranges and Accuracy Temperature, Pressure, Power, Current, Energy, Voltage 10.2.4 Test Data Logger Recording and Evaluation 10.2.5 Test Packages Air Tightness of Door/Lid Seals, Opening Force of the Doors and Lids, Durability of o f Hinges and Handles, Mechanical Strength of Shelves and Similar Components

10.6.1. Energy labelling system 10.6.2. Calculation of EU Energy Label Efficiency classes 10.6.3. Impact of EU Policy and Measures - a Story of Success

Freezing Test Ice Making Test

102 102 102 103 103 103 103 104 104 104 105 105

108 109 109 109 109 109 110 110 110 110 111 111 111 111 112 113 113 113 113 113 113 113 114 116 117 117 117 117 117


p. 7

10.10. 10.11. 10.12.

Test of Absence of Odour and Taste Refrigerator Performance Test Calorimetric Tests Refrigeration Circuit Measurement Positions

10.13. 10.14.

Test Panel Refrigeration Performance Calculation

10.16. 10.17.

Electromagnetic Compatibility Test Cooling Circuit Pressure Test according to PED

117 118 118 118 119 119 119 120 121 121 121 121 121 122 122 122 122 122 122 122 123 123 123 123 123 124 125 127 131 131

11. 11.1. 11.2.

Converting Household Refrigerators Converting Household Refrigerators from CFC-12 to HFC-134a Systems Converting Household Refrigerators from HFC-134a HC-600a Systems

132 132 133

12. 12.1.

Standards EN Standards for refrigerators

135 135

12.2. 12.3. 12.4. 12.5.

ISO Standards IEC standards Some selected US Standards for refrigerators For refrigerators relevant EU Directives

138 138 138 138

Evaporator Temperature, Condenser Temperature Suction Condition, Delivery Condition, Liquid Return, High and Low Pr essure

10.14.1 Properties 10.14.2 Equation of State 10.14.3 Extended Antoine Equation 10.14.4 Latent Heat of Evaporation 10.14.5 Ideal Gas Heat Capacity Capacity 10.14.6 Saturated Liquid Enthalpy 10.14.7 Liquid Density 10.14.8 Liquid Viscosity 10.14.9 Liquid Thermal Conductivity 10.14.10 Surface Tension 10.14.11 Saturated Vapour Density 10.14.12 Vapour Viscosity 10.14.13 Vapour Thermal Conductivity 10.14.14 Vapour Speed of Sound 10.15. Tables 10.15.1 R134a Liquid and Saturated Saturated Vapour Enthalpy and Latent Heat 10.15.2 R134a Liquid Density and Viscosity and Surf Tension T ension 10.15.3 R134a Saturated Vapour Density Density and Viscosity, Thermal Conductivity Conductivity and Speed of Sound 10.15.4 R600a Saturated Saturated Vapour Pressure 10.15.5 R600a Superheated Superheated Vapour Pressure Properties

Household refrigerator, Safety Standards for Refrigerators and Fr eezers, Electric Components, EMC Electromagnetic compatibility, Commercial refrigerator, Absorption refrigerator, Valves, Compressor, Condenser, Filter Dryer, Acoustical noise, EU Directives

EU DIRECTIVE 2003/66/EC Energy labelling of household refrigerators r efrigerators amending Directive 94/2/EC EU Low Voltage Directive (73/23/EEC) as amended 93/68/EEC. EU Pressure Equipment Directive (PED) 97/23/EC EU ATEX Directives, ATEX Manufacturers Directive 94/9/EC, ATEX User Directive 99/92/EC

12.6. CE Marking process

140 140 141 142

ANNEXES

144

Annex 1. Refrigerator and freezer appliances

144 145

Annex 1.1. European Commission DIRECTIVE 92/75/EEC Energy labelling a nd standard product information of the consumption of energy and other resources by b y household appliances Annex 1.2. EU DIRECTIVE 2003/66/EC energy labelling of household electric refrigerators, freezers and their combination

152

I like to thank Danfoss and his employees in the research for the strong technical support granted to me, the received data and detailed information, without all these support this booklet could not have been written.

Transfair Engineering: Engineering: Designing and Prototyping Prototyping of Refrigerator and Freezer Cooling Circuits. 1. Introduction: Introduction: Refrigeration Cycle - Definitions p. 8

1. INTRODUCTION 1.1. Refrigeration Cycle - Definitions Total Heat Rejected (Enthalpy difference between

compressor delivery and expansion device inlet Isothermal condenser temperature

Hi h Pre Press ssur uree (Isobaric condenser ressure)

Superheat (enthalpy difference between

compressor suction and evaporator saturated vapour condition)

(Enthalpy rises as result of the compression process)

Subcooling (the enthalpy drop

Heat of compressor

between the saturated liquid in condenser and expansion device inlet)

Compressor Delivery (enthalpy of the

Liquid Return (temperature at

super-heated vapour at the end of compression/ at compressor discharge) d ischarge)

Expansion Valve Enthalpy

end of compression)

inlet of expansion device)

Delivery Condition (Temperature at

(at the inlet of expansion device)

Compressor Suction Enthalpy (of the

Pressure Ratio : derived

superheated vapour at the start of the compression process)

Refrigeration Effect (the enthalpy difference between evaporator saturated vapour condition and the expansion valve condition)

temperature)

from the condenser and evaporator pressure

Suction Condition (compressor inlet

Low pressure

(isobaric evaporator pressure)

Volume Flow/Mass Flow (based on the refrigeration duty and the specific volume at the compressor inlet condition)

Isothermal evaporator temperature End of Evaporation (saturated vapour condition at

the evaporation temperature and pressure)

Specific enthalpy

are calculated at a number of points around the cycle (100KJ/kg 0 °C liquid)

Delta H Values : derived from specific enthalpy differences around the circle COP: Coefficient of Refrigerator Performance defined on the ratio of the refrigeration effect to

the heat of compression.

The basis of the refrigeration cycle and its circuit elements are explained in DANFOSS: Refrigeration - an Introduction to the basis, Nordborg, March 1978, http://www.danfoss.com/BusinessAreas/RefrigerationAndA irConditioning/Training+and+Education+New+design/ or on a profound level in: Althouse, A.D., Turnquist, C.H. and Bracciano, A.F.: Modern refrigeration and air conditioning, South Holland (Ill.) 1975; and Dossat, Roy J.: Principles of refrigeration. N.Y., 1981, which we cannot repeat here.

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer Cooling Circuits. 1. Introduction: Refrigeration Capacity, Thermal Losses p. 9

1.2.

Designing of Refrigerators and Freezer Circuits

The most important factor for a design of the refrigeration circuit, the compressor power etc., is to face the thermal leakage leakage of the refrigerator or freezer cabinet or chest to be kept under special temperatures (for example < -18 ° C in a *** freezer, < -12 °C in a ** freezer, < -6 °C in a * freezer, < +5 °C (or <+7 °C) in a refrigerator against an ambient temperature of 32 °C or even 43 °C for a tropical version, depending on which standard will be applied. In case of a freezer we have to add the power which is necessary to freeze down a quantity of lean meat in addition to the thermal losses of a cabinet or chest. In standards it is fixed how much lean meat in which time has to be frozen down and to which temperature, for example according to one of the ISO EN standards, min 4.5 kg lean meat (=Tylose package) package) per 100l volume in 24 h, respective for >45l volume at least 2kg 2 kg in 24h. Normally freezing power is in the t he range of 8-12 kg/100l/24h. These 2 factors together plus some reserves will decide about the size of the compressor power and the dimensions of other circuit elements. Some reserves are needed because not all the circuit elements are optimal and such systems have also to cover ageing processes. The system must be sealed to avoid leakage of refrigerant (see Transfair: Cooling circuit sealin g chapter 5). In general the design of the refrigeration circuit depends on a quite considerable number of strictly connected variables. Not optimal conditions in evaporators, condensers and capillary tubes can reduce the balances and heat transmissions and the used power of the compressor and can increase the consumption o f energy.

1.3.

Standards and Climate Classes

1.3.1.

Refrigerator and Freezer Performance Standards

Following international (ISO), not only in Europe (EN) valid standards for refrigerators and freezers performance testing exists (for electric international standardisation it is the IEC, see chapter 1.3.3. Electric Safety): (2005) specifies the essential characteristics of household refrigerating appliances, factor y-assembled and cooled by internal natural convection or forced air circulation, and establishes tes t methods for checking the characteristics. It revises the following 4 standards, which are now withdrawn: ISO EN 7371 - Performance of household refrigerating appliances refrigerators with or without low lo w temperature compartment; ISO 8187 EN 28187 - Household refrigerating appliances Refrigerators-freezers' characteristics and test methods; ISO EN 5155 - Household refrigerating appliances - Frozen food stor age cabinet and food freezers characteristics and test methods; ISO EN 8561 Household Frost free refrigerating appliances, refrigerators, refrigerator-freezers characteristics and test methods.

ISO EN 15502

Often under same number this standard are translated in EU national standards like AT (ON (ON), ), BE (IBN/BIN (IBN/BIN), ), CH (SNV (SNV), ), CY (CYS (CYS), ), CZ ( CNI CNI), ), DE ( DIN DIN), ), DK ( DS), DS ), EE ( EVS EVS), ), ES ( AENOR AENOR), ), FI ( SFS SFS), ), FR ( AFNOR AFNOR), ), GB (BSI (BSI), ), GR (ELOT (ELOT), ), HU (MSZT (MSZT), ), IE (NSAI (NSAI), ), IS (IST (IST), ), IT (UNI (UNI), ), LT (LST (LST), ), LU (SEE (SEE), ), LV (LVS (LVS), ), MT (MSA (MSA), ), NL (NEN (NEN), ), NO (SN (SN), ), PL (PKN (PKN), ), PT (IPQ (IPQ), ), RO (ASRO (ASRO), ), SE ( SIS SIS), ), SI (SIST (SIST), ), SK (SUTN (SUTN), ), and other ISO member countries have same or similar standards like JP (JIS (JIS), ), RU (GOST (GOST), ), US (ANSI/ASHREA/UL (ANSI/ASHREA/UL), ), IN (BIS (BIS), ), CN (SAC (SAC), ), BR (ABNT (ABNT), ), CA (SCC (SCC)) etc.

Such standards regulate which kind of performance tests has to be applied on all refrigerators and freezers types (see chapter 11) to make type approval (CE etc.), which ones on all refrigerators and which ones only on samples from the running production and how the volumes and consumption values have to be measured. For energy efficiency and labelling systems for household appliances, refrigerators and freezers exist in Europe EN153 (1995, new 2006), and rules 92/75/EEC, 94/2/EC and 2003/66/EC and in other arias similar regulations (see www.worldenergy.org ). In 2002 20% of sold refrigerators were of class A (low energy consumption, while 2002 already 47% as result of this labelling system. So 2003 A+ and A++ classes were introduced and since 2004 a new labelling scaling are under consideration. See Chapter 10.6. and Annex. For commercial refrigerators , not part of our booklet there exist adequate standards: EN ISO 23953 (2006) Refrigerated display cabinets – Part 1 Vocabulary, Part 2: Classification, requirements and test conditions. And for its energy labelling of commercial refrigerators it is EN 441. For absorption refrigerator there exists the EN 732 (1998): Specifications for dedicated liquefied petroleum gas appliances Absorption refrigerators.


1.3.2.

Climate Classes

In these standards all refrigerators and freezers are classified according to the ambient temperatures under which they can conserve the requested inner temperatures (C °): A freezer in a fridge-freezer model often only temperature controlled in the fridge, can defrost if kept in colder ambient as it’s climate class (see chapter 9.) Climate class Ambient Temperature from [ °C] to [°C]

Extended SN Temperate N Subtropical ST Tropical T

1.3.3.

+10 +15 +18 +18

+32 +32 +38 +43

Fresh food storage compartment t1, t2, t3 [ °C] tm [°C]

0 0 0 0

10 10 10 10

+5 +5 +5 +5

*** [°C]

** [°C]

* [°C]

Cellar compartment from [ °C] to [°C]

< -18 < -18 < -18 < -18

< -12 < -12 < -12 < -12

< -5 < -5 < -5 < -5

+8 +8 +8 +8

+14 +14 +14 +14

Electrical Safety Standards

There exist special standards which regulate the electrical safety requirements of refrigerators and freezers type approvals (CE etc.), their control and testing. Models using Isobutane or Propane have additional safety demands on their design and type approval tests (see chapter 8.2.-8.5). Furthermore the manufacturer has to insure that each produced refrigerator and freezer follow the requirement fixed for the type approval, by quality controls and inspection. Often following electrical safety tests are applied on all produced refrigerators and freezers (class 1 with PE): • Earth test, continuity of electric bounding circuit test • High voltage Test (=flash test or Dielectric strength test • Insulation test and electric strength Power and current absorbed test • • Leakage current test • Residual Voltage test (if the refrigerator and compressor co mpressor performance is improved by a capacitor). Details see in chapter 8.5.1. In addition other parameters like correct wiring, earth connection, IP54 sealing, functioning of all electrical components like switches, thermostats, signal lights, light switches, light should be inspected and/or tested. The safety standards specify which electrical safety rules the manufacturer have to respect, which electrical components acc. to which electrical standard he can use in the appliances and which kind of approval he needs. Following meanwhile international valid safety standards exist for household refrigerators and freezers: - IEC-EN-UL-J-GOST etc. Standard 60335 (2002), Part 1: Safety of household and similar electric appliances, and - IEC-EN-UL-J-GOST etc. Standard 60335, Part 2-24 (2002): Particular requirements requirements for refrigerators and and food food freezers. Amendment 1 (2005) and Amendment 2 (2007) or consolidated Standard 60335, Part 2-24 Version 6.2 (2007). - IEC-EN-UL-J-GOST etc. Standard 60335, Part 2-89 (2007): Particular requirements for commercial refrigerating appliances with an incorporated or remote refrigerant condensing unit or compressor, Vers. 1.2. The electric safety of commercial refrigerators are described in IEC 60335-2-89 and of commercial dispensing appliances and vending in IEC 60335-2-75. The IEC 60335-2-24 and 2-89 was amended 2002 and 2005 to cover potential risks originated from the use of o f flammable refrigerants; for refrigerators and freezers using u sing flammable refrigerants (R600a, R290) following was integrated into this standard - to carry out risk assessment assess ment of flammable gar refrigerants according to CEN/TR 14739 (2004) : Scheme for carrying out a risk assessment for flammable refrigerants in case of household refrigerators and freezers; and - to control flammability risk according to CENELEC Test Schedule TS 95006; see chapter 8.5.. The Amendment of 2007 did not touch test procedures, pro cedures, but text and reference to other changes or cancelled standards. Such safety standard has to be applied in addition to the performance standards of refrigerators: EN ISO 15502 (previously the 7371, 8187, 8561 and 5155, now withdrawn). The above mentioned IEC 60335-2-24 amended in (2005-04) should be respected today in case Hydrocarbon is used as refrigerant. It based on the application of the existing electrical safety standard IEC 60079-15 “Electrical apparatus for explosive gas atmospheres, Electric apparatus with type of protection ‘n’" . For further details see chapter 8.


1.4. Refrigerator Capacity The first approach to determine the refrigeration capacity and out of it the compressor size for a new refrigerator or freezer is to calculate the thermal losses of a refrigerator, freezer or fridge freezer and to add - in case of a freezer - the needed freezing capacity (Chapter 1.4.1). In case a cabinet or chest is already existing, the thermal losses and needed freezing capacity can be measured (Chapter 1.4.2.) instead of calculated. Calculation of thermal losses and freezing power , if no prototype is already available to See underneath "Measurement of the cabinet constant",

measure;

if a prototype exists.

Such calculations and measurements are only a first approach; after installing the circuit test runs have to follow to optimise the circuit, the capillary tube length and the charging of the refrigerant by - pull-down and continuous run tests - cycling tests for class designation - Energy consumption tests - Ice freeze test.

1.4.1. Calculation of Thermal Losses and a nd Freezing Power According to the selected model, the standard, the climate class to be applied following formula can be applied to calculate the thermal losses for each surface of the refrigerator and/or freezer: P= 1/s * k * A * ∆ t°

whereby:

P = s = k =

power per each single surface in kcal/h; thickness of single surface in m; coefficient of transmission of insulating material adopted in kcal/ (h*m* °C) in which the variables h=hours, m= length in meter of test specimen and °C = temperature displacement between the 2 sides of the test specimen A = surface in m² of area to be considered ∆t°= temperature displacement displacement between the 2 sides of dispersant surface.

To simplify the calculation an average thickness of o f sloping surface can be considered as well as an average material transmission trans mission coefficient [x mm polyurethane + y mm S/B (high impact i mpact polystyrene)].

Example: Double door refrigerator-freezer combination with - outer dimensions: 595w x 600d x 1385 mm - refrigerator inner dimensions: 525w x 510d x 800h - compressor area 192x190x525mm - freezer inner dimensions: 495w x 480d x 231h - refrigerator capacity: 195l - freezer capacity: 55l - insulation of refrigerator: 35mm - insulation of freezer: 50mm - thermostatic control from refrigerator: - freezer air temperature: -23°C - refrigerator temperature: 4°C-7°C, mean temperature 5 °C - compressor temperature: 88°C - condenser temperature: 55°C - evaporator temperature: -26°C - ambient temperature: 43°C (tropical) except 60 °C compressor area and 55 °C condenser area - freezing capacity measured under 32 °C ambient temperature The coefficients of transmission k are as following: - Polyurethane with Cyclopentane in densities of 30-35kg/m³: - Magnetic door gasket:

k= 0,02 - 0,025 k= 0,06 - 0,08


We neglect in the 2 door models the heat transmissions trans missions between refrigerator and freezer compartment as their sum is 0 kcal/h. Calculation:

1/thickness x k x Dimension(m²) x ∆t x pieces

Refrigerator door area: Crisper supper area: Crisper back area: Compressor upper area: Crisper side area: Refrigerator side area: Refrigerator back area: Refrigerator door gasket: Freezer side area: Freezer back area: Freezer door area: Freezer upper area: Freezer door gasket:

(1/0,035) x 0,02 (1/0,035) x 0,02 (1/0,035) x 0,02 (1/0,035) x 0,02 (1/0,035 x 0,02 (1/0,035) x 0,02 (1/0,035) x 0,02 (1/0,017) x 0,07 (1/0,05) x 0,02 (1/0,05) x 0,02 (1/0,05) x 0,02 (1/0,05) x 0,02 (1/0,017 x 0,07

x 0,525 x 0,8 x 0,525 x 0,32 x 0,525 x 0,19 x 0,525 x 0,19 x 0,51 x 0,19 x 0,51 x 0,61 x 0,525 x 0,61 x0,02 x(0,525+0,8) x 0,48 x 0,23 x 0,5 x 0,48 x 0,5 x 0,23 x 0,5 x 0,48 x 0,02 x(0,5+0,23)

x x x x x x x x x x x x x

38 38 55 55 38 38 50 38 66 78 66 66 66

x x x x x x x x x x x x x

1 1 1 1 2 2 1 2 2 1 1 1 2

= thermal losses

= 9,12 kcal/h = 3,65 kcal/h = 3,14 kcal/h = 3,14 3,14 kcal/h = 4,21 kcal/h = 13,51 kcal/h = 9,15 kcal/h = 8,29 kcal/h = 5,83 kcal/h = 7,49 kcal/h = 3,04 kcal/h = 6,34 kcal/h = 7,94 kcal/h

Total transmission losses:

84,85 kcal/h

The various figures of ∆t in the different sections of the cabinet show that the insulation thickness on the backside of the cabinet and the compressor area should be increased to reduce thermal loss and that also the space for heat transmission through the door gaskets should be as much as possible p ossible reduced and the door gaskets should be improved to improve the refrigerators. These 84,88 kcal/h are needed to face all dispersions at 43°C ambient temperatures. To obtain the thermal losses for an ambient temperature of 32°C we have to multiply the a.m. items instead of 38°C with 27°C in in the refrigerator and instead of 66°C with 55°C in the freezer (only the refrigerator's backside remains at 50°C, freezer's backside at 78°C and the compressor area at 55°C). The formula to determinate the power necessary to freeze 5 kg lean meat (Tylose packs) in 24 hours is following: P = 1/24[(G*C* ∆ +t1) + (G*Cl) + (G*C* ∆ t2)]

whereby: P = G = c = ∆t1 = Cl = ∆t2 = 1/24

Input power in kcal/h weight to be frozen in kg specific heat in kcal difference between external temperature and 0°C latent heat in kcal/kg difference between 0°C and - 18°C to calculate freezing power per hour instead of freezing inside 24 hours.

The specific heat and the latent heat for lean meat (Tylose (T ylose pack) values are as following: C = 0,77 kcal Cl = 60 kcal/kg so in this case we come to following freezing powe r: P = 1/24 [(5*0,77 kcal*32)+ kcal*32)+ (5*60) + (5*0,77*18)] = 20,52 kcal/h This freezing power has to be added to the 84,85 kcal thermal transmission losses to determine the needed compressor power which is in this case 105,37 kcal/h. As a compressor should not run permanently, but only in the range of 60-65% and 15% should be added as reserve for not optimal circuits, the compressor power should be in the range of 105,37 kcal/h * (100 +15)/62,5% = 193,88 kcal/h kcal/h Transfair can provide an Excel simulation and optimization program pr ogram to minimize thermal losses and foam consumption.

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer …Circuits. 1. Introduction: Introduction: Cabinet Constant, Reduction of Thermal Losses p. 13

1.4.2. Measurement of the Cabinet Constant In case a prototype exists, the thermal losses can be measured in a test laboratory instead of a.m. calculations. In this case a constant ambient temperature of 32 °C is created in the test room and a 10 Watt bulb heater is put inside the closed refrigerator cabinet and in a second step inside the closed freezer cabinet. In case of a larger freezer it is recommended to use a heater with a ventilator and to add the 2 entered energies (E-heater + E-ventilator). The test will stop if the heater does not increase anymore the inside temperature. Let's suppose the reached inside temperature is 46°C in the refrigerator and 51,6 °C in the freezer. In this case the cabinet constant is i s as following: Transmission losses K x A = E/ ∆ t = Watt/ ∆ t [Watt/ °C]

whereby:

K KxA ∆t Watt

is the cabinet constant the transmission losses over surface A is the temperature difference between inside and outside the refrigerant the entered energy (lamp energy or energies of used heater and ventilator). 1 Watt = 0,8598 kcal/h 1 kcal/h = 1,163Watt

In our sample:

Refrigerator cabinet constant Freezer cabinet constant

= 10Watt/ (46-32 °C) = 0,71Watt/°C = 0,83kcal/h °C = 10/ (51,6 - 32 °C) = 0,51Watt/ °C = 0,59 kcal/h °C

Optimal insulated refrigerators and chest freezers should have cabinet constant values underneath of 1. Out of this measured cabinet constant we can calculate the total thermal loss multiplying the 2 constants of the refrigerator and freezer cabinets with the surface areas and the temperature differences in t he different surface areas. Total heat loss = refrigerator cabinet constant * sum (surface areas A1, A2, A3.... * ∆t1, t2, t3. ...) + freezer cabinet constant * sum (surface areas A1, A2, A3...* ∆ t1, t2, t3...) SAMPLE: The 2 door model according to the calculation in previous chapter 1.4.1: Total heat loss = 0,83[0,525*0,8*38+0,525*0,32*38+0,525*0,19*55+0,525*0,19*55+0,51*0,19*38 0,83[0,525*0,8*38+0,525*0,32*38+0,525*0,19*55+0,525*0,19*55+0,51*0,19*38 *2+ 0,51*0,61*38*2+0,525*0,61*50+0,02(0,525+0,8)*38*2]+ 0,59[0,48*0,23*66*2+0,5*0,48*78+0,5*0,23*66+ 0,5*0,48*66+0,02(0,5+0,23)*66*2=68,35kcal/h+ 34,60kcal/h=102.95kcal/h In this case the real thermal losses are 20% above the theoretically calculated losses. To these losses the 20,52 kcal/h freezing power has to be added. This measured or calculated refrigeration capacity determines the size of the compressor so that the selected compressor should be in the range r ange of (102,95+20,52kcal/h)*100/62,5% =198kcal/h.

1.5. Reduction of Thermal Losses If the thermal losses are higher than expected or if the cabinet constant should be better than comparable cabinets we should take a closer look to the insulation, ins ulation, the construction and the manufacturing of the cabinet. Several reasons could be responsible for the thermal losses: - the thickness of insulation, - the quality of the foam, - the quality of manufacturing, - Thermal bridges, - the air tightness of the door or lid seals.

If in some areas the heat transmission will be increased, because of a construction or manufacturing faults, the cabinet constant and the energy consumption will be bad. A system is as good as their weakest points!

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer .Circuits. 1. Introduction: Polyurethane Foam Tests, Thermal Bridges p. 14

1.5.1. Foam Insulation Thickness The lower the temperatures to be reached are and the higher the ambient temperature can be the thicker the foam insulation should be. Inside the compressor compartment and in direction of the condenser the external temperature of the cabinet or chest will be slightly higher ( ∆t could be +5 till +10%), so it is useful to increase in this areas the insulation thickness to avoid weak points. In case of a skin condenser (see chapter 3.2.) with a condensing temperature of +55 °C instead of a environmental temperature of for example 32 °C ∆t is increased by 23°C; in case of a freezer with internal temperature of -18 °C and an environmental temperature of 32 ° the ∆t would be 50 °C without skin condenser; if we install on it a skin condenser of 55°C, the ∆t in the area of the condenser would be increased to 73 °C and in this area the thermal losses would be increased by 50%. Another point of insulation is the foam quality qualit y to be tested by foam tests.

1.5.2. Polyurethane Foam Material Tests Usually, sampling is effected at different spots of a refrigerator. These test specimens serve to determine the core density. The procedure is as follows: Skin 30mm Example: Core 30mm Measurements of the Foam Density in Refrigerators.

Skin 30mm A sample of approx. 10 cm x 10 cm is cut off the refrigerator. Inner and outer cover sheets are removed. The skin is cut of both cover sheets so that only the core remains; thumb-rule: the core represents approx. 1/3 of the insulation. This sample is weighed, and then the volume is determined, e.g. by plunging the sample into water. The quotient from mass and volume is defined as core density. Faster and more accurate is following method following the principle of • • •

Archimedes:

Larger blocks of up to 10 cm sides are weighted. The measured weight has the value G. A 2 l vessel with about one l l water is put on a balance and the balance with the vessel filled with water is set to 0g. A stick or wire is inserted into the foam block and without touching the vessel wall the block is dipped under the water of the vessel on the balance. The increase of weight as measured by the balance after full dipping of the foam block is equal to the increase of volume (1g water=1ml), so that the Density d [g/ml] = Weight of foam block G [g] / Increase of weight on balance V [g]

Usually, approx. 800 g of material are shot into a polyethylene bag, presenting a diameter of about 30cm. 2 to 4 hours later, a sample of 10cm x 10cm x 10cm is cut from the middle of the foam produced in this way. This test specimen is weighed and the weight either divided by the calculated volume or by the weight of water pushed away by the test specimen dipped in water according to the a.m. principle of Archimedes. The quotient from mass and volume is defined as free rise density . Measurement of the foam density in case of test shots.

The dimensional stability can be determined in the following way: Cut/saw a test specimen, size approx. 10 cm x 10 cm, off the refrigerator. Remove the cover sheets. Determine the dimensions of the test specimens (height, width, length). Store one test specimen for 24 hours at -30°C, another one for 24 hours at +80°C. Determine the dimensions again afterwards.

Dimensional Stability.

-

Compression Strength . Foam samples of about 30x30x30 up to 40x40x40mm

foam flow direction and 90° to flow flo w direction).

of cabinet measured in 2 directions (in PU

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer .Circuits. 1. Introduction: Polyurethane Foam Tests, Thermal Bridges p. 15 Sample on fridge-freezer combination :

-

2x4 foam samples taken of side walls 300mm from front side (2x2 in side walls of fridge compartment, 2x1 in middle separator, 2x1 in side walls of freezer compartment) 1 sample top, 1 sample bottom, 3 samples in back wall (2 in fridge back b ack wall, 1 in freezer back wall).

For Cyclopentane driven PU foam minimum compression strength str ength should be 140-145kPa. For Cyclopentane/Isopentane driven PU foam minimum compression strength should b e 135-140kPa. Such compression strength measurement replaces today in praxis more and more the foam density distribution measurements. Following material and equipment is needed: • a beaker of hard paper of about 0.6-1 litres (for examples Messrs. Kamphemann, No. 600, non-waxed, Volume 660 cm³ from Heinrich Kamphemann, Kamphemann, P.O.Box 2604, D-49016 Osnabrück, Tel.: 0541-32037, Fax: Fax: 0541- 23565, • laboratory stirrer, 0, 5W, 1300/min) with disk 60-65 mm, • laboratory balance balance 0,1g accuracy, water bath, knife/saw and glass bar to be used in following procedure to determine the reaction parameters: • The components are tempered in a water bath at 20°C +/- 1°C. • The paper beaker is put onto the balance and tarred. • Component A is submitted first, and component B is added subsequently in the corresponding mixing ratio; the weighed-in quantity should be in total 70g. • Both components are then mixed at 1300m-1 for approx. 1 0 sec. • The stop-watch is started as stirring begins. Tests: Cream Time is defined as time interval from fro m start of stirring to visible volume expansion in the beaker. • String Time is defined as time interval from start of stirring to the moment when it is possible to draw fibres out of the reaction mixture by means of a glass bar. • Rise Time is defined as time interval from start s tart of stirring to visible ter mination of volume expansion. • Raw Density. After the foam surface has cured, the foam is cut off directly at the edge of the beaker. The beaker is put onto the balance. The mass indicated i ndicated is divided by the volume of the beaker (660 cm ). Verification of the Reaction Parameters in the Laborat ory.

●

A continuous quality control should measure regularly the follo wing: Measurement of the foam reaction INSPECTIONS INTERVALS parameters of test shots: the free rise Free rise density of the core at least twice a day density and string time at least twice a String time at least twice a day day; Shot weight at least twice a day Comparison of set and really reached Dimensional stability at least twice a day shot weight every day by random Compressive strength at least twice a day sampling. once a day Dimensional stability: samples should be Mixing ratio once a day taken from refrigerators/doors every day Distribution of core density compressions/pressures of the machine at least twice a day in order to check the dimensional Operational compressions/pressures stability, and if possible, the compressive strength str ength as well. The verification of the correct mixing ratio is also necessary.

Assurance of a Continuous Quality.

•

•

•

•

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer .Circuits. 1. Introduction: Polyurethane Foam Tests, Thermal Bridges p. 16

1.5.3. Thermal Bridges To locate thermal bridges, so called cold bridges a good digital thermometer with tolerances of 0.2 °C and a point feeler can be used. The appliances will be cooled down. A digital thermometer with a point feeler can measure colder surfaces caused by thermal bridges to the inside. A modern method uses thermo-graphical cameras. Weak points are often - metal sheets or tubes which connect the outside with the inside, - bad designed or manufactured door or lid gaskets which allow warm air to enter into the refrigerator or freezer, - bad seals holes for the electrical cable of the lamp-switch-thermostat combination inside the compartment, for the capillary tube of the thermostat, for the evaporator tubes o r for the water drainage tube, - bad positioned anti dew coil. One of the weakest point are the sealing between door and cabinet, the door gasket area where the outer steel with high thermal t hermal conductivity of the cabinet and door comes co mes very near to the cold area of the t he compartment only isolated by the door gasket. In cases that the steel continues to the inside we have a strong cold bridge, in addition increased in case of a freezer or fridge freezer fr eezer by a hot (+55 °C) anti dew coil. Sealing between door and cabinet.

Also by a small distance of about 5 mm between the food liner and a nd the door liner in the conical area of the food- and door liner the cold bridge can be reduced. But the space depends on design of the door profile, if it can absorb slight door tilting after use and from the strength of the hinges and their adjustment possibilities. If the space is too small and the construction cannot absorb absor b tilting of door after use, the door will not close properly. Reduced space between food liner and door liner.

Design and quality of the door gasket .

Last not least the design of the door gasket and the quality of their manufacturing and their welding is very important. In closed condition the door gasket profile sections, separated by thin PVC walls touching the plastic liners, should built up at least 3 further temperature zones between warm outside and cold inside, good ones have even 4 zones in addition to the inside and outside. Even after years of use the gasket should be flexible and close the door tight. Only very few first class door gasket manufacturers can deliver such quality. We recommend co-operating with important and experienced door gasket manufacturers like the German company REHAU in Rehau, near Erlangen, or the Italian company ILPEA, Malgesso (Varese). The purpose of this test is to ensure that the gaskets of the doors or lids of the appliance adequately prevent any abnormal ingress of the surrounding air. The test are executed under an ambient temperature between 16-32 °C on the switched off appliance with the same temperature inside the cabinet. A strip of paper 50mm wide and 0.08 mm thick and with a suitable length shall be inserted at any point of the seal, and the door or lid closed normally on it. The seal shall be assessed asse ssed by checking that the strip of paper does not slide freely. The most unfavourable point can be found by lightening the closed cabinet from inside and checking the light from outside of all seals. The test should be repeated after the durability test acc. New ISO 15502 (previously according to chapter 11 of the a.m. ISO standards 7371, 5155 and 8187 (see in chapter 10.3. of this booklet under “Mechanical tests”). Testing of the air tightness of door or lid seals.

Door Gasket Only in freezer: AntiDew De w coil

d t e e n i m a b o a F C

Foamed Door

Transfair Engineering: Designing and Prototyping of Refrigerator …Circuits. 2. Compressor, Replacement of CFC-12 Compressors, Compressor Capacity p. 17

2. COMPRESSOR In this chapter we can and will not consider how compressors can be developed or optimised using different geometrical, electrical and other characteristics and different kind of refrigerants with different pressure ratios, swap volumes etc. Such considerations should be part of compressor manufacturing study which is not part of our work. We only have to concentrate on the correct selection and use of already optimised compressors co mpressors in the cooling circuit of household refrigerators.

2.1. Replacement of CFC-12 Compressors Today all CFC-12 compressors in household refrigerators are replaced by HFC-134a or by HC-600a (Isobutane). The first question for the user is if the R12 substitutes reach the same or better refrigeration efficiencies as the R12 compressor and which of the substitutes are better and more reliable. The answer at moment is that the reached efficiencies are very similar if the compressor and cooling circuit were really optimised for the refrigerant, independently if R12, R134a or R600a compressors were used. But the specifications for the circuit elements and the specific problems of designing, manufacturing and servicing are different and need to be checked in each application and for the environment of the market and service conditions for which it is produced. HC-600a (Isobutane), HFC-134a and HC-290 (Propane) compressors reaches today excellent energy efficiencies and should – according to many research institutes - not differ in their energy efficiency (Coefficient of Performance) significantly, though some say sa y that they heave evidence that the HC-600a also theoretically, not only practically as seen today should have about 5 % higher efficiencies if other conditions are the same. In the last 5 years a lot of efforts were made to improve energy efficiency of HFC-134a and of HC-600a compressors which today reaches higher efficiencies (COPvalues, see Chapter 2.10) as the old R12 compressors not as far optimised. Specially in the European market dominated by HC600a in the household refrigerator market, the efforts made were so much that in practice R600a models reaches today significantly higher COP-values than equivalent R134a models.

Energy efficiencies.

A mixture of HC-600a (Isobutane) and HC-290 (Propane) in the range of 40:60 has the advantage that it can replace CFC-12 in CFC-12 compressors without modifying the compressor design: Such a mixture matches R12 compressor designs because almost the same displacement volume can be used. But the mixture can have in some refrigeration applications problems concerning energy efficiency due to the temperature glide in condensation and evaporation of the 2 components.

Drop-in solutions.

But pay attention:

Using inflammable Hydrocarbon in a CFC-12 refrigerator needs a safety control of the design according to IEC 60335-2-24 (1997-08) and a design modification (see (s ee chapter 8).

Reliability and lifetime. Concerning the reliability and lifetime HC-600a (Isobutane) and HFC-134a are proven to be very reliable today while HC270 compressors because of higher pressure conditions are under stronger stress, have a much higher noise level , and a smaller lifetime, at least if we concentrate on smaller compressors used in household refrigerators. Also the

lifetime of compressors using the Isobutane-Propane mixture seems to have lower reliability and lifetime and have a much higher noise level than Isobutane compressors because of t heir demanding working conditions.

Because of about 70-80% bigger displacement volume needed in a HC-600a compressor the first R600a compressors became larger and the space for the compressor compartment could be a problem, but meanwhile this problem is diminished strongly because of new design developments, so that a wider range of capacities can already be reached without increasing the overall dimension of the compressor. Compressor dimensions and needed space.

HFC-134a compressors are very similar to CFC-12 compressors. With moderate modifications and investments such compressors can be made in previous CFC-12 compressor factories. Also the switching from CFC-12 refrigerators to HFC-134a refrigerators is quite simple and does not need relevant design changes and investments. Though HC600a compressor manufacturers have made bigger investments in research and factories the today’s price levels of HFC-134a and of HFC-600a compressors do not differ significantly. Investments and costs.

Transfair Engineering: Designing and Prototyping of Refrigerator …Circuits. 2. Compressor, Replacement of CFC-12 Compressors, Compressor Capacity p. 18

2.2. Compressor Capacity There exists no standard system to define sizes of hermetic compressors used in the household application, but more or less common categories to characterise hermetic compressors. In Europe and in the USA there are standards to define the size of the refrigeration capacity of compressors under comparable evaporating and condensing temperatures, the so called CECOMAF or ASHRAE standards.

2.2.1. HP Value The previously used HP designation has been more and more abandoned, because the HP value does not define any refrigeration characteristics of the compressor.

2.2.2. Nominal Displacement In 1963 Danfoss introduced the compressor definition by the nominal displacement of refrigerant in cm³/rev., which are till today the most important figure to compare compressor capacities as long as the same refrigerant is used. If compressors with different refrigerants are compared to each other this parameter does not help. For example R600a has half of the volumetric capacity as R12 or R134a and needs a nearly double displacement to reach the same refrigeration capacity. The motor sizes of R12 compressors and R600a compressors for the same refrigeration capacity are approximately the same while R134a compressors need often a slightly bigger size.

2.2.3. Refrigeration Capacity Today the refrigeration capacity is used more and more for the size definition. But the refrigeration capacity is not easy to standardise and needs further definitions like evaporating temperature, condenser temperature, frequency and ambient temperatures. Today 2 different standards in the world are used to compare refrigeration capacities: the European standard CECOMAF and the American standard ASHRAE (see these standards for further details). The difference is that the European standard measures the cooling capacity under conditions without the sub cooling of the liquid while the ASHRAE states the capacity based on a sub cooling of the liquid to the ambient temperature (32 °C). Last increases the nominal capacity by about 18-25%, depending which refrigerant is used.

2.2.4. Coefficient of Performance The most important value to compare efficiencies of different compressors under same ambient conditions and same temperatures to be reached in freezer or refrigerator (last can be only used if refrigerator is without a freezer) and same refrigeration capacity is the COP-Value: COP-Value: The Coefficient of Performance is the ratio between electrical electrical power input and refrigeration capacity output under ambient ambient temperature of 32°C, 38°C or 43°C, condenser temperature temperature of 55°C and liquid sub cooling to ambient temperature of 32°C , 38°C or 43°C according to American ASHRAE standard or without sub cooling (that means liquid temperature = condensing temperature) according to European CECOMAF standard. The higher the COP value is the better the compressor perform. But high performance compressors needs good electrical conditions often not exist in tropical areas. Higher performing compressors for tropical areas are just started to be developed, but never can reach high performance values without improving electrical supply. See Chapter 2.10. Since more that 12 years European refrigerator manufacturers drain the cold condensed water from the evaporator at backside of the foodliner to a tray on top of the compressor to cool down the shell (see chapter 5.2.2.-5.2.4.). By this way about 12-15% of energy consumption could be reduced and the COP value increased. Further important definition factors for compressors are: Compressor water tray.

Transfair Engineering: Engineering: Designing Designing and Prototyping of Refrigerator Refrigerator and…Circuits. 2. Compressor, Compressor, Starting Characteristics, Electrical Diagram, Diagram, Lifetime Lifetime

p. 19

2.3. Starting Characteristics In general the starting characteristics of compressors differentiate between

low starting (LST) and high starting torque

(HST):

Normally single phase AC motors are supplied in following 4 electrical versions: RSIR: RSCR: CSIR: CSR:

Induction motor with resistance (PTC) start Induction motor with resistance (PTC) start and run capacitor Induction motor with capacitor start Induction motor with run and start capacitor Low starting torque compressors are using normally PTCs without run capacitors (RSIR) or with a run capacitor (RSCR) while high starting torque compressors compressors are using starting capacitors.

The starting device PTC is a semiconductor with a positive temperature coefficient; when the PTC is cold it permits current passing the semiconductor. During operation (current passing the PTC) it becomes heated and the resistant increases so that only sufficient current can pass to keep it warm. PTC starters allow the start winding to be cut-in only for a limited time; if the start run-up is prohibited, no overloading of the start winding is possible. The cooling down time of a PTC is about 3.5 min. The more it is cooled down the longer it allows the cut-in in the subsequent start run-up. Therefore the system depends also on the standstill time defined by the thermostat settings which should be min. 3 min. for a small compressor and 5 min. for a larger one. In the past also current or voltage relays were used instead of a semiconductor PTC; but PTCs have a lot of advantages in comparison to relays: - higher lifetime because of no wear and no relay chatter, - dependable protection of the start winding as above explained, - the PTC function independently from over- and under-voltages, - no radio or television noise, - same PTC can be used for all compressor sizes, - easy conversion from LST to HST compressors by only changing the starting device. Important for the lifetime of the LST compressor is that the compressor have not to start to build up compression against high pressure in the condenser. To avoid this heavy duty in the starting of a synchronous motor in the past a relays, today mainly a PTC is added to the electrics of the compressor. Inside of about 5 min the PTC is cooled down to allow a new start of the compressor, a sufficient time to reach a pressure-equalised system. s ystem. High starting torque compressors use a start capacitor to improve their life time in bad electrical environments like lower voltages as made for (for example 170V instead of nominal 230V) or unstable frequencies (clock problems). The line impedance (voltage drop during start) is normally < 1 V/A in developed countries while we aspect in many developing countries, like in India, Middle East, Black Africa voltage drop > 1.5 V/A – in addition to the severe tropical climate (>43°C). For such electrical and climate conditions special models have to be selected with start capacitor, but still for cost reason many refrigerator producers’ uses standard LST compressors with PTC instead of HST compressors with a start capacitor. Start capacitor will cost about € 5-6,50 more, depending on the size.

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R134a and R600a COP optimised compressors are often not designed for developing countries with difficult electrical and climate conditions. Especially R600a compressor made for this conditions ar e still rare.

Pay attention:

A run capacitors in a RSCR or RSR system normally increases the efficiency (COP) of a compressor by 8-10 %; therefore it can reduce the energy consumption by 3-5 %. In case of a HC-600a compressors with a general temperature decrease in the compressor the effect of the run capacitor is even significantly higher.

2.4. Electrical Diagrams All compressors in addition have an external or an internal (built-in winding protector) motor protection.

2.5. Lifetime In general the compressor life depends on how far the compressor is protected against motor overloads. The careful dimensioning of the refrigeration system, a thorough assessment of the operating conditions of the compressor at expected limit of loads. If it is over o ver dimensioned the energy efficiency will be reduced, if it is under dimensioned the lifetime will be reduced. Long working life and problem free operations of hermetic compressors depend on 4 conditions: 1. The compressor must have enough starting torque to overcome the pressure conditions in the refrigeration system at moment of start. 2. The motor must have sufficient breakdown torque to overcome the loads which occur in connection with start run-ups and during operation. 3. To allow refrigeration systems with LST compressors a pressure equalisation the stand still time is minimum 3 min. often even 5 min. which must be insured by the thermostat. t hermostat. 4. Very important is the well-dimensioned condenser surface and a good ventilation of the compressor. The max. condensing temperature must not exceed 60 °C, at peak time 70 °C in the highest ambient temperature. The winding temperature of the compressor motor should not exceed 110 °C for a R12 system, 120 °C for an R134a system and 125 °C for an R600a system plus 10°C during short peak loads. Compressors working with lower voltages as designed for increase their temperature during operation in a way that after few years running the compressor oil becomes greasy so that the mechanical resistance will even increase under the bad electrical power supply conditions and the compressor coil inside the oil will burn down. That is the main reason why the life time of compressors in developing countries are often less than 6 years while in developed countries it is very, very seldom that a compressor in a household refrigerator has to be replaced during the time the refrigerator is used (about 10-12 years in developed d eveloped countries).

2.6. Heavy Duty That means such a compressor can even run if the supplied voltages are lower than the nominal and under bad environmental and electrical conditions. This can be reached by increasing the motor power of a compressor with the same nominal displacement capacity: Consequently such a system can be either used also for high evaporating temperatures or for low evaporating temperatures under unstable electrical supplies with under-voltages and frequency (clock) problems.

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Often such heavy duty compressors are over dimensioned in comparison to the nominal refrigeration duty for such application. The oversized compressor will surely increase the energy consu mption, but will last much longer.

2.7. Evaporating Temperature LBP, MBP

or HBP letters are used for low, medium and high back pressure to operate in low, medium or high refrigerant evaporating temperatures. In our applications we only use LBP compressors but with different oils and sealing depending which refrigerants are used, for example mineral oil for R600a or R12 and Polyol ester oil for R 134a. The last is hydroscopic and can cause a lot of problems in the manufacturing of R134a refrigerators while the R600a refrigerant can burn and need special precautions regarding electrics to fulfil IEC 600335-2-24 (1997-08) standard.

2.8. Comparison between R134a and R12 Compressors The thermodynamic properties of R12 and R134a are slightly different. Because of the different curves of the pressure and temperature crossing each other at 20 °C the volumetric capacity of R134a is below the one of R12 at low boiling conditions while at high boiling conditions it is the opposite. o pposite.

2.8.1. Pressure-Enthalpy Diagrams of R12 and R134a Such a refrigeration process as shown in the diagrams (next page) is normally used to determine the nominal LBP capacity on a calorimeter. The conditions have the following specification: Evaporating temperature: -25°C Condensing temperature: 55°C Inlet throttle device: 55°C liquid Outlet throttle device: super-heated to 32 °C Ambient temperature: 32°C As it can be seen already on the diagrams the latent heat of R134a is considerably higher than the one of R12; that means at a given capacity a lower mass flow. Furthermore different angles of inclination of the borderline between liquid and vapour can be seen in the diagrams. The T he less steepness of the R134a borderline indicates a capacity advantage in connection with a falling condensing temperature.

2.8.2. A Comparison Test from Danfoss Such differences can be taken out of the enclosed table from Danfoss (Hermetic LBP refrigerating systems for R134a, September 1990, made on a 5cc compressor. This T his test was one of the first tests test s made with R134a (1990) and the R134a compressor and systems where not yet optimised as today. Therefore the efficiency differences to R12 s ystems are quite high:

Transfair Engineering: Engineering: Designing Designing and Prototyping …Circuits. 2. Compressor, Compressor, Heavy duty, Comparison Comparison between and R12 and R134a R134a Compressors Compressors Sections 1. Enthalpy difference

2. Mass flow differences

3. Volume flow at the throttle device 4. Sub cooling influences

Parameters

Evaporating pressure (-25°C) bar Condensing pressure (55°C) bar Enthalpy i2 (-25°C/32°C) kJ/kg Enthalpy i1 (55°C liquid) kJ/kg Enthalpy difference i 2- i1 kJ/kg Compressor capacity W Mass flow ( capacity/(i2- i1) x3600/1000 ) kg/h Gas temperature -inlet cylinder °C Specific volume m³/kg Volume flow - inlet cylinder m³/h Inlet throttling device °C Specific volume dm³/kg Volume flow dm³/h Enthalpy i1 (55°C liquid) kJ/kg Enthalpy is (32°C liquid) kJ/kg Enthalpy difference i 1- is kJ/kg Capacity with sub cooling to 32°C: Mass flow i 2-is kJ/h Capacity without sub cooling to 32°C:Mass flow i 2-i1kj/h Performance relation (i 2- is )/(i2- i1 )

R12

R134a

1.237 13.66 373 254 119 95 2.87 94 0.2 0.57 55 0.841 2.41 254 231 23 407.5 341.5 1.19

1.067 14.912 431 279 152 87 2.06 84 0.28 0.57 55 0.927 1.91 279 244 35 385.5 313.1 1.23

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Conclusions (Part 1): 1.

The enthalpy difference is with R134a considerable larger than with R12. For further details see Chapter 7. Refrigerants.

2.

The mass flow can be calculated out of the capacities which have been measured on the 5 cc displacement compressor. If the temperature at the inlet of the cylinder is known it is possible to calculate the volume flow. In our case the temperatures based on practical measurement. Please note the lower temperature level with R134a .

3.

The conditions before the throttling device differ between R12 and R134a. The volume flow with R134a is 80% of the volume flow with R12; that means that the resistance of the capillary tube must be increased and the capillary must be adapted to the needed higher pressure difference and lower mass and volume flow. An ideal system is operating in such a way that the refrigerant at the inlet of the capillary tube is as close as possible to the liquid/vapour borderline in the pressure /enthalpy diagram. For further details see Chapter 4. Capillary tube.

4.

The influence of using sub cooling before the throttling device is larger for R134a as for R12 systems. R134a systems with a sub cooling of 32°C increases the nominal capacity by about 23% while with R12 the nominal capacity is only increased by 19%.

5.

As a thumb rule a given displacement with R134a will have a nominal LBP refrigerating capacity which is 88-90% of that of R12. In few cases it will be possible to use the same displacement with R134a as with R12, but in general it will be necessary to switch to the next bigger displacement.

6.

Often the evaporator- and freezer design used for R12 do not need to be modified for the use of R134a. Only by an increase of the displacement which means a bigger nominal capacity and if the previous used condenser was just sufficient it could be necessary to increase the surface of condenser. Also important is for a freezer the more steep inclination of the R134a system in comparison to the R12 system. This means a relatively higher load on the condenser during the pull-down. Therefore the condenser surface of a freezer often have to be increased and some models under tropical conditions which in the past could work without oil coolers with R12 could need now oil coolers which means 30% bigger surface and half used for oil cooling. This can be easily checked if the superheat measured on the condenser side is too high (see in Chapter 3. Condenser, 3.4. Oil cooler, 3.6. Testing condensers).

7.

Not to be neglected in the evaporator and condenser design should be the cross sections of channels . The miscibility of refrigerant and oil is important. Ester oil was selected for this reason to be used for R134a; however it is not as perfect as mineral oil for R12 or R600a. Ester oil can pass the circuit. To avoid thermal effects all cross sections should be equal and oil pockets or unnecessary use of parallel channels should be avoided. This is for all refrigerants useful to improve the efficiency but for R134a a must.

8.

The Polyol ester oil is hydroscopic, react with chlorine and mineral oil and therefore a much higher cleanness standard on all cooling circuit elements , their fabrication and their assembly during the refrigerator production have to be applied (see Chapter 7.2). Therefore the dryer must be improved (Union Carbide XH7 as desiccant or similar materials with 3 Angstrom


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pores). But the thermal reliability and stability of R134a/esteroil systems in comparison to R12/mineral oil systems are better. One severe quality problem of compressors is the humidity already in oil, which should not exceed 1/10 of dryer capacity (about 1g), that means 100mg water (125ppm for 280 ml oil). 9.

If system components are not changed 10%

10.

R134a can escape through minor leaks than R12. Therefore circuit and in leak detection are needed .

less R134a charge

are needed in comparison to R12. higher standards in soldering operations, in sealing the

By switching from R12 to R134a compressors and by switching from R134a to R600a compressors the leading manufacturers of compressors and also the leading refrigerator producers have made a lot of efforts to improve the energy efficiency of their systems. In comparison to old R12 systems the new CFC free systems are much more efficient and the energy consumption much lower. But some of this improvement cannot be used in developing countries with low voltages and clock problems as some of the new compressors are more sensitive in this aspect as old not optimised ones. Further details can be taken in the following chapters.

2.8.3. A Comparison Test of R134a and R12 Compressors from National Matsushita Furthermore please find enclosed the 2 tables with comparison data of reciprocal using a piston and of rotary compressors of National Matsushita for CFC 12 and for HFC 134a refrigerants which came to similar results: R12 vs. R134a R134a reciprocal compressor comparison comparison (on model D120LRAA 115V 6HZ0 ) R12 vs. R134a rotary compressor comparison on a 13 cu ft (370l) cabinet (Model NR-D37V1)

kWh/day

Energy Consumption

Btu/h Kcal/h

Amount of Charge

Refrigerant Condenser size Compressor model (100V 60 Hz) Refrigerant charge g Energy consumption acc. to JIS kWh/mo % Running time

at 30°C % at 15°C %

Capacity

Evaporation Temperature

CFC-12 A RA48L 185 36.6 Base 57.9 29.8

HFC-134a A RA48L 185 38.8 +6.0% 63.5 31.3

A+B RA48L 190 37.1 +1.0% 59.0 32.9


At 30°C Cont. Run

Freezer °C Fresh food °C Evaporator inlet °C Evaporator outlet °C Discharge –2 °C Shell °C Condenser outlet °C Condenser pressure kgf/cm²G(psig) Suction pressure kgf/cm²G(psig)

-24.1 -15.2 -31.0 -29.5 90.3 97.9 38.9 9.8 1.02

-21.0 -15.0 -29.0 -28.5 85.5 94.0 39.0 10.1 0.89

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-23.4 -14.0 -30.3 -29.0 80.0 92.0 36.7 9.6 0.84

Conclusion (Part 2): Needed Design Improvements Compressors for R134a need higher power (+7-15%) to reach the same refrigeration capacity in comparison to R12 compressors. To avoid higher costs and energy consumption by switching from R12 to R 134a systems following steps should be made: 1) 2) 3) 4)

Elimination of thermal bridges, Improving of condenser efficiency (see National Matsushita table and effect), often to be realised by an increase of the condenser surface, Improving of evaporator efficiency, especially to avoid oil pockets pockets and reductions of cross sections, Optimisation of the system.

It will be described later how condensers and evaporators can be improved and the system can be optimised. We only want to mention how thermal losses can be eliminated. First the door gasket sector, the construction but also the welding of the door gasket can be improved by avoiding air leakage in the corners and by reducing the space between door and cabinet. The construction of this closing sector and of the door gasket can be improved by using specialised companies like Rehau in Erlangen/Germany or Ilpea in Malgesso/Italy, the 2 mayor suppliers of door gaskets in Europe. Eur ope. We also recommend looking carefully at the construction of the door cabinet section of such refrigerators and freezers which have very low energy consumption to find an optimal opti mal own construction. Last not least areas towards the backside condenser and towards the hot compressor department need could easily be seen on the calculation of thermal losses in the previous chapter.

bigger insulation

as it

With all these efforts an increase of power po wer of the compressor by switching from R12 to R134a systems can be avoided.

2.9. Comparison Tests of R600a, R134a and R12 Compressors from Necchi Necchi has compared in test series different compressors already optimised for the refrigerant used. They have first tested the compressors only with a calorimeter, than they have mounted them on household refrigerators from running productions. Following tests results were achieved: .

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2.9.1. Compressor COP Tests Compressor performance comparison of R600a and R134a were measured on a calorimeter. The T he R600a compressor performance values contain 2 figures, the first without run capacitor, and the second with run capacitor R600a

R134a

Model

Displace- Cooling capa- Energy efficiency Model ment (cc) city (kcal/h) ratio(w/w) HGTR4.5 4.7 60 0.99/1.10 ETR3.5 HGTR5.5 5.5 74 1.05/1.16 ETR4 HGTR6.5 6.5 86 1.10/1.17 ETR5 HGTR8 8.2 109 1.12/1.21 ETR5.5 HGTR9 9.1 122 1.23/1.34 ESR7 HGTR11 10.6 140 1.28/1.39 ESR8 HGTR13 12.5 160 1.30/1.41 ESR8.5 HGTR15 15.1 203 1.29/1.40 ESR11

Displace- Cooling capa- Energy efficiency ment (cc) city (kcal/h) ratio (w/w) 3.50 65 0.93 4.10 75 0.98 5.12 101 1.07 5.55 112 1.10 7.00 127 1.16 7.75 148 1.15 8.20 160 1.17 10.60 212 1.15

2.9.2. Fridge/freezer Tests using R600a, R290/R600a Mixture, R134a and R12 Compressors Aim of these tests of Necchi was to identify the behaviour of refrigerators on charges of different gases and compressors. Only the charge quantity and capillary tube were optimised while the evaporators and condenser were not modified. Necchi uses refrigerator models from running productions.

Single Door Refrigerators Nominal Volume Refrigerant Charge (g) Compressor type(cc) Fridge temperature(°C) Freezing temperature(°C) Energy conservation(kWh/24h) Running %

140 l 170 l 190 l 140 l R12 R600a R12 R600a R12 R134a R600a R12 R134a R290/R600a 110 40 120 58 75 73 27 80 87 25 4 6.5 4 6 3 3 4.5 4 4 4 5 5 5 5 5 5 5 5 5 5 -18 -17.5 -9.4 -8.7 -8.3 -9.1 -8.5 1.12 1.07 1.16 1.06 1.09 0.93 0.87 1.14 1.13 1.08 47 51 43 42 52 47 48 37 40 43

Double Door Refrigerators Nominal Volume Refrigerant Charge (g) Compressor type(cc) Fridge temperature(°C) Freezing temperature(°C) Energy conservation(kWh/24h) Running %

180 l + 60 l R12

260 l + 70 l R12

R290/R600a 110 5 5 -20.5 1.65 66

50 5 5 -19.5 1.52 58

R290/R600a 8.5 5 -13 2.47 69

8.5 5 -16.5 2.32 63

Vertical Freezer Nominal Volume Refrigerant Charge (g) Compressor type(cc) Freezing temperature(°C) Energy conservation(kWh/24h) Running %

120 l R12 95 5.5 -18 1.43 40

290 l 250 l 140 l R290/ R600a R290/ R12 R600a R12 R134a R600a R600a R600a 55 54 50 160 65 110 100 37 5.5 13 8.5 7 11 4 5 8 -18 -18 -18 -18 -18 -18 -18 -18 1.50 1.41 1.48 1.86 1.62 1.25 1.37 1.24 49 35 40 55 62 56 55 51

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Conclusions (Part 3) The R134a application is producing a slightly lower capacity than the R12. The cooling capacity of R600a is approximately 50% in all evaporating temperatures that mean that the displacement of the compressor must be increased to reach the same performance on a given application. R290/600a mixtures were very si milar in this point to R12 applications.

Cooling capacities.

R600a applications show in these tests better COP values than R134a applications. The difference even will be increased by applying run capacitors in so called high efficiency versions which seems to increase the R600a version slightly stronger than the R134a version. But this t his needs further systematic studies. Coefficient of performances.

The needed increase of displacement of an R600a compressor was smaller than theoretical expected. The actual temperatures of compressors along the thermostatic controlled cycles were lower than calculated for R600a with the effect that the gas densities and consequently the volumetric efficiency of R600a compressors were better than calculated. Run capacitors will even increase this effect. R600a displacement increase.

The sensitivity on charge tolerances differ very strongly between R134a and R12 on one side and R600a on the other side. R12 and R134a household refrigerator systems tolerate 10-20 g charge variations without a significant effect on the energy consumption while R600a reacts - not only because of a much lower quantity of charge - very sensitive on deviations from the optimal charge quantity. +/-5 g deviations changes changes the behaviour of the system very very much. (Personal remark: Many refrigerator producers try to keep the charging tolerance of R600a household refrigerators in the limit of 1g). Charge tolerances.

HC blends can be considered as drop-in solutions for existing appliances for R12 as long as the refrigerator fulfils the safety requirements and tests according to IEC600335-2-24 (1997-08). R290/R600a drop-in solution.

R600a compressors produce 2 dB(A) less noise than R12 compressors and 3-4 dB(A) less than R134a compressors. But on some models a slight increase in noise were noticed and the cause was not understood and need further studies.

Noise.

160kcal/h can be obtained by 8 cc R134a or by 13 cc R600a. The increase of displacement of an R600a compressor cannot be always made inside the same housing and in some cases a step-up in the compressor family is required. Overall dimension of compressors.

Lubricant.

R134a needs the use of Polyol ester lubricant with some bad consequences in comparison to R600a and R12

systems: - much higher hydroscopic in comparison to mineral oil used in R600a compressors, - slightly lower thermal stability in connection with anti-wear anti -wear additives, - solubility, not all ester oils get it at all temperature ranges, - limited material compatibility (chlorine etc.).

Such lubricant problems of R134a systems have bad effects on the performance as a result of the so called sludge formation of the capillary tube which does not exist e xist in R600a or R12 systems. Reasons for the sludge formations are: - Excessive moisture content . Through hydrolyse of the ester oil an acid can be produced which react to carbossilates (a metallic salt) This effect can be reduced by strong cleanness controls on all circuit components and by much more efficient dryers (3A pores on molecular sleeves). Any additive which can act as catalyst must be avoided. -Excessive oxidation of the oil. As final result of oxidation, ester decomposition and their reaction with metal ions can be a metal salt, which can be avoided by high vacuum before charging. - Chlorine. Chlorine in combination with heat decomposes ester with the same result as mentioned above. Therefore chlorine often used in productions as cleaning material must be avoided and such pollution need to be controlled. -Temperature. Under bad conditions higher temperatures are reached with R134a as with R600a systems. Such higher temperatures causes deterioration on ester oil, if not compensated by higher quality requirements for ester oil for R134a as required for mineral oil for R12 and for R600a. Such effects are strongly increased by impurities coming from system pollution (mineral oils, oligomers extracted from plastics, etc.

Sludge formation.

The stricter control on cleanness of all R134a refrigeration circuit components is vital for its long life, but it improves the efficiency of all systems. But also the selection of mineral oil in R600a systems and the quantity of R600a in the oil is not unproblematic. If in big refrigerators the quantity of R600a becomes too high the lubricant viscosity can be strongly effected and microscopic foam can be built between the friction surfaces so that the film can break if traditional naphtenic lubricant were used. So also the selection of lubricant is important for R600a compressors. Solubility of R600a in mineral oil and foaming.

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The humidity is also a problem for R600a systems to reach high quality. Humidity can be removed from evaporator and condenser by dry air, but it is today practically impossible in the refrigerator factories to remove it from the refrigerant itself and from the compressor oil. These are the 2 severe quality problems as it is already in the refrigerant and in the oil, both should not exceed 1/10 of dryer capacity (about 1g), that means for the compressor oil 100mg water (125ppm for 280ml oil). Humidity.

The flammability of R600a is their weak point even it is relatively small risk because of the small charging quantity present in domestic appliances. On the compressor the risk can be prevented by using a flame-quenching overload protector and PTC starting device which eliminates any ignition point near the compressor. (Other measures to be taken concerning light and thermostat etc. will be considered in Chapter 8 ).

Flammability.

As consequences of the above mentioned items needed for R134a compressors, especially the higher costs of the Polyol ester oil and needed the higher purity and cleanness standard for R134a the R600a compressor price should be equal or lower than the R134a compressor . But this cost calculation is only valid for displacement ranges reachable inside the same overall dimension so that no upsizing is needed. (Other costs concerning other electrical components of the refrigerator like ex-proof lamps or thermostats - if needed in single cases of constructions - are not considered here, but will be considered in Chapter 8). Compressor costs.

Necchi came to the conclusion that R600a systems for household refrigerators are under economical, ecological and efficiency point of view feasible and the global overall costs should be not higher than the one for R134a, considering the changes needed to prevent any risks coming from the flammability of the gas. E. Biscaldi: CFC substitutes (R600a and R134a): performance, manufacturing, and costs from the compressor point of view. ECO-Refrigeration. Conference on Hydrocarbon Fluids in Domestic and Commercial Refrigeration Appliances. 13-14.2.1996.

2.11. Energy Optimised Compressors In the last 3 years a lot of improvements, especially for R600a models, were made to reduce energy consumption. Today we differ between 4 energy efficiency versions: - the standard compressor versions as offered in the past with COP- values of 1.45-1.6 at –20°C evaporating evaporating temperature, - energy optimised systems (without using run capacitors) with COP-values in the range of 1.7 to 1.75 at –20°C evaporating temperature, saving energy consumption of 5-7% in comparison to standard versions, - high-energy optimised systems by using run capacitors with COP-values in the range of 1.9 to 2.0 at –20°C evaporating temperature - last only reachable today by R600a s ystems, saving energy consumption of 20 up to 33% in comparison to standard versions, and - Variable speed compressors , saving energy consumption of 30-40% in comparison to standard versions. A compressor with variable speed costs about double as much as a standard one while the high efficient one costs DM 3.5 up to DM 8 more that the standard ones as result of the 4 µ capacitor. The prices between standard and energy optimised ones differ today already in the ranges of price fights (DM0-2) and can be neglected. By more compact coils and better designed electromagnetic fields less electrical energy is needed for same cooling capacity, but in this case stable electrical conditions are needed for high COP values. In addition the cylinder in and outlet, specially the tube connection to the suction side was improved: Instead of using the complete shell volume to separate oil from gas only a limited gas volume is used in so called “semi-direct” and specially in “direct inlet”. These design modifications improve the COP ratio by 5-7% without increasing significantly the costs. In the high energy efficient model a run capacitor is added to compensate the coil inductivity and reduce the cos phi phase shifting. The problem is that the energy optimised and high energy optimised models are developed till today for regions with stable voltages and frequencies and good impedance (ratio V/A) and not for developing countries with bad electrical supply conditions. Only very few compressor manufacturers like Danfoss started already to optimise models designed for tropical areas with often higher Voltage fluctuation in the range of 185-230Vac instead of 198-254 Vac (Danfoss with their new FT models replacing the previous G models). But in this field at lot of further progress can be reached.

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2.12. Variable Capacity Compressors In 1996 a new generation of compressors with variable cooling capacity using electronically driven motors together with a reciprocating mechanism were developed. With this kind kind of control the compressor runs continuously and modulating its capacity according to the needs. It can archive optimal compressor and heat exchange pressures by eliminating or minimising stoppages and restarts with a result of strong energy savings of about 30% and a reduction of the noise level in comparison to conventional on-off compressors. Often even the compressor’s size can be reduced. The advantages for the consumer are lower energy consumption, faster freezing, better food conservation, higher temperature stability and lower noise. Also a longer lifetime for the compressor can be expected, but still need to be verified.

Embraco VCC models. Electronic

controls as needed to control the variable speed of the compressors are normally also used to control the temperatures of the food compartments (by ther mocouples instead of thermostats).

Danfoss grant a program called RS +3 which allow to calculate and select the right Danfoss compressors upon fundamental cooling circuit data under http://www.danfoss.com/Germany/BusinessAreas/RefrigerationAndAirConditioning/Product+Selection+Tools+details/R Splus3.htm

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2.13. Compressor testing and performance data EN 12900 (2005) : Refrigerant compressors - Rating conditions, tolerances and presentation of

manufacturer's performance data. This European Standard specifies the rating conditions, tolerances toler ances and the method of presenting manufacturer’s data for positive displacement refrigerant compressors. These include single stage compressors and single and two stage compressors using usin g a means of liquid subcooling. This is required so that a comparison of different dif ferent refrigerant compressors can be made. The data relate to the refrigerating capacity and power absorbed and include correction factors and part-load performance where applicable.

The COP data according to EN standard excludes subcooling, while the US ASHRAE COP measurement data includes includes subcooling. For example Danfoss NLE8.8KK.4 Energy-optimized Compressor R600a 220-240V 50Hz without run capacitor: EN 12900/CECOMAF Evap. temp. in °C Capacity in W Power cons. in W Current cons. in A COP in W/W

-35 62.7 70.1 0.49 0.89

-30 84.0 81.3 0.52 1.03

-25 110 93.0 0.56 1.18

-23.3 120 97.3 0.58 1.23

Typical test conditions for R600a compressor

Condensing temperature Ambient temperature Suction gas temperature Liquid temperature

ASHRAE

-20 141 106 0.61 1.33

-15 -10 -35 -30 179 223 76.7 103 121 138 70.2 81.2 0.67 0.75 0.49 0.52 1.48 1.61 1.09 1.27

EN 12900/CECOMAF 55°C 32°C 32°C no subcooling

-25 134 92.8 0.56 1.45

-23.3 147 97.0 0.58 1.51

-20 -15 -10 173 218 272 106 120 138 0.61 0.67 0.74 1.63 1.81 1.98

ASHRAE 54.4°C 32°C 32°C 32°C

Methods of Testing for Rating Positive Displacement Refrigerant Compressor s and Condensing Units. This standard applies to the methods of testing for rating single-stage positive-displacement positi ve-displacement refrigerant compressors and condensing units that (a) do not have liquid injection and (b) are operated at subcritical (saturated) temperatures of the refrigerant. It also applies to the methods of testing for rating single-stage positive-displacement refrigerant compressors and condensing units that (a) incorporate liquid injection that is controlled by a steady flow rate method and (b) are operated at subcritical (saturated) temperatures of the refrigerant. US-Standard ANSI/ASHRAE 23(2005):

EN 13771 -1 (2003 /2005): Compressors and condensing units for

refrigeration - Performance testing and test methods - Part 1: Refrigerant compressors. This part 1 of the European Standard applies only to refrigerant compressors and describes a number of selected performance test methods. These methods provide suf ficiently accurate results for the determination of the refri gerating capacity, power absorbed, refrigerant mass flow, isentropic efficiency and the coefficient o f performance. This standard applies only to performance tests conducted at the manufacturer's works or wherever the equipment for testing to the accuracy required is available. The type of measuring instrument and the limits li mits within which measurements shall be made are listed in normative annex A. The electric safety of compressors have to be controlled by compressor manufacturer according to IEC EN 60335-1 and IEC EN 60335-34 and a CE conformity declaration of compressor manufacturer including the conformity to EU Low Voltage Directive 73/22/EC and the EU PED 93/23/EC has to become part of type approval of the th e refrigerator.

2.14. Labelling of Compressors with Flammable Gas (R600a, R290 etc.)

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator Refrigerator and freezer Cooling Circuits. 2.12. Compressor Compressor testing and performance data

p. 30

Transfair Engineering: Engineering: Designing Designing and prototyping of Refrigerator Refrigerator … Circuits. Circuits. 3.2. Condenser, Skin Condenser Condenser on Refrigerator Refrigerator or Freezer Freezer Cabinets

p. 31

3. CONDENSER 3.1. Static Condensers Static condensers

are air cooled condensers mounted on the back side of a refrigerator or freezer. There exist 2 types:

3.1.1. Wire-on-Tube Condensers On a tube serpentine with normally a horizontal tube serpentine vertical wires are welded to increase the heat exchange surface. Nowadays there exist high efficient condensers with smaller distances between the wires which allow a higher heat exchange on the same overall dimension of the condenser.

3.1.2. Tube-on-Finned-Plate Condensers On a normally vertical tube serpentine finned plates, made by r oll forming, are mounted.

3.1.3. Condenser Constant In a first approach the following formula can be used for the calculation of the static condenser (for tube-on-finned-plate or wire-on-serpentine condensers): Ks =

whereby:

Compressor kcal/h*1,25 --------------------------------------------------- -----------∆t

Ks = condenser constant in kcal/h °C ∆t = the temperature difference between the condensing temperature and the ambient temperature which is normally in the range of 23 °C. In our sample the condenser should have the Ks value

Ks = 190*1,25/23 =10,33.

This Ks value allows us already to determine from the condenser suppliers' catalogue (for example Bundy or Benteler) which condenser with which Ks value can be selected inside the maximum size of the cabinet width and height. There exist tubing of 5mm or 6mm, different serpentine's radius and different distances and diameter of wires (pitches) welded on the serpentines (in case of wire-on-tube condensers is selected).

3.1.4. Condenser Capacity A second approach of selection of condensers allows the foll owing formula. The condenser's capacity Qk can be calculated:


p. 32

Qk = Qo + N - Qh (kcal/h)

whereby: Qo = N = Qh =

Evaporator capacity and increase of enthalpy up to the cylinder Compression work in kcal/h Heat emission from compressor pot.

The N and Qh values can be received from the compressor co mpressor manufacturer for the selected compressors. By this way the condenser's capacity can be calculated out of the evaporator capacity or vice versa. For an air-cooled condenser the condenser capacity Qk can be also calculated according to the formula: Qk = k * A * ∆t(kcal/h)

whereby: k= A= ∆t =

Transmission coefficient (Kcal/h x m² x °C) Effective condenser area (m³) Temperature difference between condensing temperature and air temperature in °C.

The transmission coefficient and the effective condenser area can be granted by the condenser manufacturer. The ∆t will be defined by the measured ambient and condensing temperatures; therefore we can calculate out of the needed condenser capacity value Qk the condenser size, which has the maximum width of the refrigerator and the length according to the calculated condenser area. The condenser capacity can also be expressed by the circulated quantity of the refrigerant r efrigerant in the following way: Qk = G * ∆i = G * (i1-i2)

whereby: G= ∆i = t1 (i1) t2 (i2)

the circulated quantity of refrigerant [kg/h] enthalpy loss from the condenser inlet to the condenser outlet [kcal/kg) designate temperature and enthalpy respectively at the compressor discharge discharge connector/ condenser inlet; the condition at the condenser outlet, while t 3 is the ambient temperature at the condenser's surface and air.

Out of this data which can be taken from similar systems by measurement or during optimisation of the system itself we can calculate the effective condenser area in the following way: A= ( G*∆ i)/(k*∆ t) = [Gx(i1-i2)]/[k*(t 2-t3)*m³]

3.1.5. Condenser Transmission Coefficient or U-Value The transmission coefficient or U-value describes the quantity of heat in kcal/h which can be removed per m² at a temperature difference of 1°C or 1 K. The U- value is almost the same for the 2 condensers types. The first table described the U-value in dependence on the temperature differential at a tube spacing of 60mm. The temperature differential is in general in the range of 15-16 °C for rear condensers; in this case the U-value is in the range of 10-11 kcal/h xm²x °C.


p. 33

By varying the distance of the tube (see the next table underneath) the Uvalue of the condenser is influenced. For example for tube spacing of 45 mm the U-value is nearly double as high as for tube spacing of 100mm. But the reduction of the tube spacing has limits and it strongly increases i ncreases the material costs. Often lowest relative material costs per output unit are reached with a tube spacing of 60 mm. The wire spacing is economically at 6mm with wire diameter of 1,5 mm. The tube size selected is normally 5-6 mm dia. The 5 mm needs fewer refrigerants but for a larger refrigerator or freezer it needs high maximum condensing pressure. The bigger tube results in longer pressure equalising time of the system and this can cause starting trouble. The reduced charge inside a 5 mm condenser results in lower equalisation pressure and improves the starting conditions for smaller compressors during initial start-up. But the 5mm condenser and discharge tube causes larger pressure drops and during start and pull-up of the compressor the starting capacity of the compressor will be reduced, especially if it starts from high equalising pressure.

3.1.6. Condenser Surface (acc. to Danfoss) To select a static condenser following graph of Danfoss for M/LBP compressor (2 poles, 50 HZ) can be used for a climate class N. The given U-value anyhow can vary, depending on air circulation and type of material used in the condenser. For other climate classes the surface of a given condenser type with fixed coefficient can be recalculated for the smaller ∆ t in ST and in T class.

3.2. Skin Condenser In a skin condenser the refrigerator or freezer outside walls are used as a condenser. The condenser tubes are mounted on the steel sheets by adhesive foils. A good contact between tube and steel plate is important. Under subtropical conditions normally the whole backside of a cabinet is sufficient if the tube spacing is in the range of 60-100mm. For A freezer an anti-dew coil is in addition needed.


p. 34

3.2.1. Skin Condenser on Refrigerator or Freezer F reezer Cabinets See sample sketches beside and construction. Because of higher surface temperature in range of 40°C near the skin condensers the foam insulation must be increased to reach same energy efficiencies and energy consumption.

3.2.2. Skin Condenser on Chest Freezers The condensing temperature should be kept as low as possible in regards of the compressor's life time and energy consumption; that means at an ambient temperature of 32 °C the condensing temperature should be below 50 °C and in tropical conditions underneath 60 °C. If these conditions cannot be maintained, oil or fan cooling of the compressor must be used to avoid strong reduction of the life time of the compressor.

Transfair Engineering: Engineering: Designing and prototyp… Circuits. 3.2. Condenser, Skin Condensers on Chest Freezes, Condenser Capacity, Increase of Insulation p. 35 Skin type condenser for chest freezer (32°C ambient temperature): Relation between gross volume, tube length, tube distance and k-value (go along the array inside the 3 grids):

3.2.3. Necessary Increase of Insulation of Skin Condenser Refrigerators and Freezers By switching from conventional condensers to skin condensers also the foam insulation thickness have to be increased. The heat transmission depends on the temperature difference between outside the cabinet and the inside (see Chapter 1.4.1.Thermal losses). If for example under subtropical climate conditions (38 °C) the outer temperature is increase to the condensing temperature (55°C) of the outer cabinet walls an increase of 20% of heat transmission and energy consumption is expected. Only if the insulation will be increased by 20% plus the tube diameter of the compressor a similar si milar energy consumption can be reached.

3.2.4 Sheet Cover on Condenser Similar aesthetic results as with a skin condenser can be reached when a refrigerator backside condenser is covered by a steel plate. The bottom and the top side must be open to use for the ventilation of the condenser a chimney effect. If the steel plate itself is used as condenser the condensing surface of this plate has to be used to calculate the U-value.

Transfair Engineering: Engineering: Designing and prototyping of Refrigerator… Circuits. 3.6. Condenser, Testing Condensers, Condenser Capacity, Comparison Test p. 36

3.3. Anti-Dew Coil

Bad Cold Bridge Foamed Door

Tension and Quality Quali ty problems Foamed Door

Door Gasket Upright freezer or fridge freezers need an anti-dew coil because of the high Magnetic Strip temperature difference between outside and inside to raise the temperature of the Plastic Liner cabinet front area beside the door to avoid dew fall. In addition this coil is a part of Anti-Dew Coil Plastic Liner Anti-Dew Coil the condenser which will reduce the condensing temperature. Important for the d t d t e e e e n n construction is to avoid thermal bridges between the inside and the outside i i Steel m m b a a b Side a o cabinet; this depends mainly on the link between the steel cabinet and the plastic o a Panel F C F C food liner. In so called cold bridges the heated steel warms up the inside. To insert it into the front profile can cause tension in i n the steel liner joint and can cause planetary problems. There are 2 ways of connecting this coil to the system: 1. the most efficient anti-dew way is to connect it between the discharge Foamed Door Foamed Door connector of the compressor and the inlet of the condenser. But it can cause a thermal bridge. 2. The other way is between condenser outlet Door Gasket Door Gaske Magnetic Strip Magnetic Stri and capillary inlet, in which anti- dew coil temperature is already Plastic Liner Plastic Line lower.

Anti-Dew Coil

Steel Side Panel

d t e e n i m b a o a F C

Anti-Dew Coil

Steel Side Panel

d t e e n i m a b o a F C

Only if bad links are used and if insulation thickness is low the dew coil effect should be reduced by inserting the coil between the condenser outlet and the capillary inlet and their position should be placed more away from the front side. Optimal position of anti-dew coil and insulation to inside

3.4. Oil Cooling Condenser In such oil cooling condenser compressor oil is cooled in the condenser to remove superheat. A partial condensation of this refrigerant takes place in the oil cooling condenser. From the oil cooling condenser the refrigerant is conducted through the oil-cooling coil of the compressor where the enthalpy increases because the refrigerant absorbs heat from the compressor oil. Afterwards the refrigerant is drawn to the main condenser where the final condensation takes place as already described previously. In the a.m. figure the Mollier diagram (i-log p) is shown and refers with t 1, t2, t3 to the oil cooling condenser. In this diagram it can be seen that a large portion of the superheat of the compressed refrigerant between the t 1 and t2 points are removed by the oil cooler. The optimum oil cooling is reached by dimensioning the oil cooling condenser to remove the superheat of the compressed gas and a partial condensation of the refrigerant is produced to prevent the thermal increase in the cooling coil from creating superheat. In his way the increased enthalpy of i3-i2 is achieved to reach the lowest temperature as possible in the entire oil-cooler and to reach an optimum value of the internal heat transmission coefficient of the oil cooling coil. To reach an optimum oil cooler the temperature's increase on the oil cooler cooler coils between the oil cooler should be measured. It is recommended that 50% of the total condenser surface should be used for an oils cooling condenser. Oil cooling condensers need compressors with oil outlet and a nd oil inlet tubes.


3.5. Fan Cooled Condenser Chest freezers in tropical conditions often use fancooled condensers to reduce superheat and if a statical condenser needs more space as available behind the chest. Such a unit consists of a condenser, normally a finned condenser, a fan and a compressor. The advantages of such a fan cooled system are that the condensers need less space and it can be often easier installed or serviced. The disadvantage is the fan noise, more frequent services (fan failures, collected dirt in the condenser) and it is often more expensive than a static condenser. The U-value is highest when the condenser is mounted horizontally and lowest at vertical position. The capacity increases by the air velocity. (See: Literature: Cube, H.L.V., and Tofahr, G.: Formes économiques de condenseurs pour armoires frigorifiques ménagers).

3.5.1. Fin Coil Characteristics The characteristics for such fin coils are: - the spacing of fins (2-10 mm) - their thickness (0,2-0,5mm) - their corrugated or plan surface - their material - the method of fixing to the tube (around 10mm dia), the good thermal contact between tube and fin (fin holes with small flanges) and - the tube spacing between coils (25-30mm). It depends on the spacing how fast it needs cleaning. The U-value falls if the fin spacing is reduced so that a larger surface only gained by increasing the fin quantity in a given space will also reduced the utilised surface. Smaller spacing often increases the noise level. Like in case of all other condensers the tube layout of the finned condenser should ensure a minimum of pressure-equalisation time, which is achieved by locating the inlet on the top and the outlet on the bottom and by b y continuously declining of the tube coil so that liquid pockets can be avoided. To avoid in some cases a large pressure drop and to reduce in other cases the tube cross section a parallel flow system (2 tubes parallel passing the fin condenser) can be used. Examples for a finned condenser unit from fro m Danfoss. Condenser area (32 °C ambient temperature ) Condenser Code No. 119-0081 119-0082² Surface area m² 1.16 1.73 Compressor M/LBP R12 0-10 8.5-15 capacity cm³ HBP R12 0-5.5 4.5-8.5 displacement LBP R504 ² With cooling baffle 18 15.6 k-Value (kcal/h x °C x m²)

119-0085² 3.22 12-21 7.5-15 10-15

119-0088² 4.28 1812-21 12-18

17.3

18.7


The compressor capacity is expressed by the compressor co mpressor displacement in cm³. The table applies to a 2 poles 50 Hz compressor in the range of M/LBP (-40 °C to - 5°C) and HBP (-5 °C to +15 °C). The recommended condenser surface is sufficient for ambient temperature of up to 32 °C and the air velocity at the condenser inlet is approximately approxi mately 1m/sec. For higher ambient temperature the compressor size and the condenser size have to be increased by using the calculation used in the last part of this chapter about condensers.

3.5.2. Possible Solutions for the Air Ducts

3.6. Testing Condensers Condenser determination and selection.

So we have following possibilities to determine the condenser:

1. By taking the data sheets of the condenser manufacturers and the requested value for the compressor power (already previously explained); 2. By measuring the condenser alone in the following way:

3.6.1. Calorimetric Measurement 3. By testing the condenser mounted on a refrigerator. By measuring the condenser alone the compressor is replaced by a heating element to keep the condenser inlet temperature constant at a superheat of 100 °C. At the condenser outlet a capillary tube is fitted to remove the condensed refrigerant under fixed settings (for R 134a for example 0,7x4.000mm). To get defined conditions the suction pressure (evaporation pressure) and hence the circulated quantity of refrigerant are regulated until the liquid level is constant in the sight glass. Since there is only one point of loading where this constant level in a given system occurs (position of equilibrium of the system), only one single measurement per condenser size is possible and needed. T here exist 2 possibilities to measure the condenser capacity now: One theoretical possibility is a flow meter to be mounted instead of the calorimeter, which is for household refrigerators not easily because of the low quantities of refrigerants. In this case the condenser capacity can be calculated by multiplying the circulated quantities in kg/h by the enthalpy difference between the compressed gas superheated to 100 °C and the liquid at the lower limit curve:

Transfair Engineering: Engineering: Designing and prototyping … Circuits. 3.6. Condenser, Comparison Test of Condenser Capacity, Condenser performance Standards p. 39

Qk = G*(t2-t3) = K*A* ∆ T=k*A*(t2-t3)[kcal/h]

The U-value is calculated on the bases of the condensing temperature minus the temperature at the condenser inlet.

It is easier for small household refrigerators (see figure) to use a calorimeter instead of the flow meter, so that the quantity of refrigerant can be calculated out of the measured temperatures by the formula:

circulated

Qk = G*C(t 1-t2)

whereby:

G = Quantity of refrigerant (kg/h) C = Specific heat content (kcal/kg x °C) to be taken out of the data sheet of the refrigerant t1 = temperature at inlet ( °C) t2 = temperature at outlet °C)

The same formula can be used to compare different condenser types by using water as refrigerant.

3.6.2. Comparison Test of Condenser Capacities To compare different condensers to each other a simple test set-up can be used and the a.m. formula allows calculating their capacities. In this case either -

the water is passed on a constant velocity and with a defined inlet temperature and the outlet temperature is measured or the temperature difference between inlet and outlet is recorded and the water flow is measured with the flow meter. So 2 condensers are easily compared by this method either by keeping the circulated quantity of water constant and recording the difference of temperatures (inlet/outlet) or by keeping the temperature difference constant and recording the circulated quantity of water.


3.6.3. Standards of condenser performance testing and test methods The following standards of condenser performance testing and test methods have to be applied in EU and many other areas: (2003 /2005): Compressors and condensing units for refrigeration r efrigeration - Performance testing and test methods - Part 2: Condensing units. EN 13771-2

(2000): Condensing units for refrigeration - Rating conditions, tolerances and presentation of manufacturer's performance data. EN 13215

EN 327 Air cooled refrigerant condensers, Heat exchangers. Forced convection air cooled refrigerant condensers. T est procedure

for establishing performance.


Transfair Engineering: Engineering: Designing and prototyping of Refrigerator… Cooling Cooling Circuits. 4. Capillary Tube, Heat Exchangers, Capacity Calculation and Tests p. 42

4. CAPILLARY TUBE AND HEAT EXCHANGERS The capillary tube must be adapted to the changed refrigerant characteristics, i.e. dif ferential pressure, mass and volume flow etc. The ideal system is operated in such a way that the refrigerant at the inlet of the capillary tube is as close as possible near the liquid-vapour borderline in the Mollier Pressure -enthalpy diagram. Practical and theoretical evaluations show that the resistance of the capillary tube must be increased when switching from R12 to R134a. In a LBP refrigerating system with the same compressor capacity the change can be described as a 20-25% reduction of the flow if measured as Nitrogen flow at 10 bar inlet pressure. This increased resistance of the capillary tube reached by prolongation of the tube or by reduction of the diameter will also increase the pressure equilibration time during the standstill period which can have effects to increase the restarting time and perhaps needs to modify the thermostat differential. The switching from R12 to R 134a gas should not affect much the gas velocity.

4.1. Capillary Capacity Calculations There exist some calculation formulas about the capillary capacity Pc[l/min] = Pf [kg/h] x Psv [m³/kg] x 1000/60

whereby:

Pf = value describes the refrigerant quantity produced by the compressor in kg/h Psv=value steam specific gravity quantity in m³/kg and the factor 1000 to transform m³ in litres and the factor 60 to transform hours in minutes.

For example a particular refrigerator operating at the condition -25 °C and at super-heating to 32 °C with a R12 compressor of 95W and an R134a compressor of 87W had following mass flow: R12-system: 0.17m³/kg x 2.87 kg/h = 0.488 m³/h = 8.13 l/min R134a-system: 0.23m³/kg x 2.07kg/h = 0.476 m³/h = 7.93 l/min This would result in a tube with an internal diameter of 5mm to a gas velocity of 6.9m/sec for R12 and of 6.7m/sec for R134a. To explain the a.m. formula we assuming following condition: 1. The condensing temperature is 55 °C, 2. The selected compressor has a displacement of 2,6 kg/h of R134a. 3. The evaporating temperature to be reached is -30 °C and an absolute pressure of 0.864 kg/cm² acc. to the Mollier diagram of R134a and the system is nearly ideal acc. to the Mollier diagram for R134a, that means the outlet of the capillary is vapour only. In such a case following specific volumes can be assumed: - liquid: 0.72 l/kg. - vapour: 0.2245 m³/kg. In such a case the Capillary capacity for R134a in l/min is as following: Pc[l/min] = Pf [kg/h] x Psv [m³/kg] x 1000/60

= 2.6 x 0.2245 x 1000 /60 = 9.728 9 .728 l/min

There exist also a formula about the capillary capacity as a result of condensation pressure, diameter and length of the capillary using Nitrogen passing the capillary as follows: ________________ Va = 2.35 x √ p² -1

xd

2.5

whereby:

xl

-0.5

Va = capillary capacity with Nitrogen gas passing in l/min


P = condensation condensation pressure in kg/cm² at 55°C d = capillary internal diameter in mm mm l = length of capillary in mm _______________ ________________________ 2,5 -0.5 For example: Va = 2.35 x √ p² -1 x d x l = 9.728 l/min = 2.35 x √ (14.907² -1) x 0.71 2,5 x l -0.5 l -0.5 mm= 9.728l/min /(2.35 x 14.28 x 0.424 ) = 0.684 l = 3.2 m But according to our experience such formulas are a first approach and the length and the diameter should be finally tested with methods as described in the next chapter. If other system components are not changed in a LBP system and same compressor capacities are chosen and similar gas velocities are reached the refrigerant charge by switching from R12 to R134a refrigerant should be about 10 % less. We recommend asking the supplier of the compressor which capillary tube diameter (normally 0,71 or 0,79mm inner dia.) and which length (about 3-4 m for the R 134a) he recommends as minimum and maximum length and there seem to be no way as to determine the optimal length of the capillary but by laboratory tests. Like usually such test first test each refrigeration circuit element separate (see for example the testing method of capillary tubes) and after optimisation of each element the system in total have to be tested as later explained to control interference between the elements on each other. Danfoss grant a program to select upon cooling circuit data the right capillary tube diameter and length called DanCapTM 1.0 http://www.danfoss.com/Germany/BusinessAreas/RefrigerationAndAirConditioning/Product+Selection+Tools+details/DanCap. htm

4.2. Capillary Tube Tests By switching from R12 to R134a the length of the capillary has to be increased or the diameter dia meter to be reduced to increase the flow resistance and to reach similar gas velocities. If the same compressor capacity is used as for R12 such a change can be described as a 20-25% reduction of the flow flo w if measured as N 2 flow at 10 bar inlet pressure.

Test Apparatus But the capillary can be also optimised by varying their length or diameter and by measuring the reached pressure drop with following test apparatus consisting of a gas bottle, a reducer with a manometer, a capillary tube with known capillary characteristics, a second manometer and the capillary tube to be tested. With such a test apparatus and variations of parts to be used different tests can be made: 1. It is possible to measure the pressure drop of a capillary tube. If the capillary tube C 2 is not connected to the manometer 2 the pressure p2 on manometer 2 is equal to the atmospheric pressure; if the capillary tube C 2 to be tested is connected to the manometer 2 the difference between the now measured pressure p 3 on the manometer 2 to the atmospheric pressure at the outlet of the tested capillary tube C 2 is equal to the pressure drop inside the capillary tube C 2. 2. By positioning of the gas bottle on a balance and removing the capillary C 1 and manometer 2 it is possible to measure the weight of gas passing the capillary in time and to calculate the corresponding capillary capacity in l/min for the used liquid or gas. 3. On this apparatus such a test tes t can even be made with liquid R134a pressurised to the 14.9 bar at 55 °C, so that real conditions as existing in a refrigeration circuit can be simulated. Also R60 0a pressurized to 6,7bar at 55°C in water bath can be u sed , if R600a


is exhausted to open air. If a capillary tube is too short or has a too large diameter, so that too much refrigerant liquid enters into the evaporator and reduces the evaporation surface can also be measured by the temperature increase in the entry area of the evaporator. So the size of this area filled liquid liq uid can be measured. Following standard can be applied: ANSI/ASHRAE Standard 28 (1996) (RA 2006): Method of Testing Flow Capacity of Refrigerant Capillary Tubes. It provides a uniform procedure for testing capillary tubes by determining the dry nitrogen flow capacity under specific test conditions so the procedures may serve as a primary standard for use by all test laboratories. Provides a basis for agreement between capillary tube manufacturers and users, and provides a standard procedure against which all other methods of tests may be checked. Dual units of measurement.

4.3. Heat Exchanger Optimum system efficiency can be reach by installing a heat exchanger between compressor suction tube and capillary to ensure The sub cooling or a capillary tube should be in the range of 3K (while such a system for an expansion valve should be in the range of 5K).

sub cooling.

For this reason 1.5-2m of the capillary tube is welded along the suction tube. Instead of welding also a PE shrink film can be used to connect the suction with the capillary tube. Sub cooling of HFC-134a increases the nominal capacity by about 23%, 4% more than in a CFC-12 model. So it is a must for a HFC-134a system. Also for R600a such sub cooling is strongly recommended to improve energy efficiencies.


Transfair Engineering: Engineering: Designing Designing … Cooling Cooling Circuits. 5. Evaporator, Evaporator, Cold Cabinet Cabinet Tube-on-Sheet, Tube-on-Sheet, TOP or Skin Skin Evaporators, Evaporators, with Freezer, Freezer, Two-door

p. 46

5. EVAPORATOR There exist different types of evaporators and it depends on the construction of the refrigerator which type can be used.

Evaporator capacity and k-value As the heat transfer of the evaporator corresponds to the compressor capacity at the relevant operation conditions, the evaporator area can be calculated from the formula: Q = K*A* ∆t

whereby:

Q = evaporator capacity in Watt K = transmission value in Watt/m²* °K (k-value) A = surface in m² ∆t = mean temperature difference in °K between refrigerant and ambient air at the evaporator.

This formula is only a first approach because it disregards certain thermal losses, caused for example by pressure drops in the suction line.

5.1. Roll-Bond Evaporators In the past the mainly used evaporator for household appliances was the aluminium roll-bond type which has an excellent k-value of between 6-8 W/m²* °K. The channel spacing for such types is normally approximately 30mm. They are electrolytic anodised or enamelled and the tube connectors are made with butt-welded Al-Cu tubes to connect on it steel tubes.

5.1.1. Suction Accumulators R12 evaporators have suction accumulators on the last part of the evaporators or as an extension of the suction line after the evaporator to be able to receive refrigerant charge variations and to ensure that refrigerant which does not evaporate in the evaporator e.g. during low loads will evaporate before passing into the suction line and the compressor. In case of roll bond such accumulators are built in (normally 15-20% of the internal volume of the evaporator): In R600a evaporators such suction accumulators should be avoided to reduce the amount of charge into the system. In single tube designs (the most common design) the capillary tube is inside the suction tube. In 2 tubes designs it is separated (see above picture). The first is cheaper, but the last one allows making a preferable gap between inlet and outlet temperature. The weak point is the seal of the capillary tube mounted in the evaporator inlet. Leakage in this section will cause short circuiting and loss of capacity.

Transfair Engineering: Engineering: Designing Designing and Prototyping Prototyping … Cooling Cooling Circuits. 5.2 Evaporator, Evaporator, 2-Door 2-Door Tube-Sheet Tube-Sheet Evaporators, Evaporators, Vertical Freezer Evaporators Evaporators

p. 47

5.1.2. Channel Cross Section There is an optimum size of the channel cross section. If it is too small, the pressure drops too much across the evaporator with the result that the compressor capacity cannot be completely utilised. If the cross section is too large the speed of the refrigerant becomes to low and oil can accumulated in the evaporator with the effect that the evaporative capacity reduces. Such accumulation of oil can even put the oil pumps in the compressor out of order. The speed of the refrigerant should be in the range of 4-5m/sec. By this speed oil accumulation will be avoided. HCF-134a do not separate as good from Polyol ester oil as HC-600a from mineral oil or CFC-12 from mineral oil so that ester oil passes the whole refrigeration circuit much easier. Therefore any reduction of the cross section or pockets in which the oil can be accumulated must be avoided in HCF-134a systems much more than in CFC-12 systems. In R600a systems performance reductions because of pressure drops are even worse because of lower absolute pressure of R600a. Therefore the tube diameter is needed to receive a refrigerant speed of about 4-5m/sec and any reduction of cross sections should be avoided. This was one of the reasons - beside of cost reductions - why roll bond evaporators which can have variable cross sections because of their way of manufacturing and which can have smaller cross sections in the bending area were replaced repl aced by tube-on-sheet evaporators with always correct cross sections. In general for all refrigerants optimised cross sections of channels improve strongly the efficiency. Pressure drops on evaporators can be measured: the temperature difference in a stable system (not duri ng pull down) between the evaporator inlet and outlet should be in the range of 1 °K.

Samples: The channel cross sections are in the

range of 22mm². If by this cross section the channel length exceeds 8m +/- 2m -depending on the compressor size and the evaporator temperatures, the pressure drops will already strongly reduce the utilised capacity. To avoid such pressure drops with larger channels length, parallel flow has to be used.

In practice bent roll bond refrigerators always face pressure drops in the bent area because of reduction of the channel cross area on the bends. To avoid pressure drop a doubling of the channel to 2 parallel channels in the bending area or an increase of the channel size will help. How can pressure drops be measured?

Pressure drops can be easily identified when the temperatures are lower at the outlet of the evaporator than in the inlet. A pressure drop across the evaporator corresponding to 1K in a stable condition (for example -30 °C) is acceptable for refrigerator appliances. We mention "stable conditions" because the pressure drop is at the beginning of the pull-down of a freezer always high; the evaporating temperatures are at this stage high and therefore the compressor circulated more refrigerant at high evaporating temperatures as at low ones: the pressure drop dr op will be the largest at this stage.

5.1.3. Evaporator Types, Sizes and Forms The type, size and form depends first on the temperatures to be reached inside the refrigerator and freezers and the ambient temperatures to be faced (see ISO and DIN standard classes SN, N, ST, T in the beginning of this report).


p. 48

Roll bond forms A and B are typical for so called "cold cabinets", refrigerators without freezer compartment. Form C and D are typical for *star refrigerators and form E and F are typical for ** star refrigerators. *** star refrigerators are made out of form E and F by adding a rear plate to E and side plates to F and to isolate the freezer section from the refrigerator section. Normally *** star refrigerators have a separate evaporator for the refrigerator because it is very difficult to reach the different temperatures in the 2 sections of the *** star refrigerator by one evaporator and screening (see underneath chapter "Screening and drip trays").

5.1.4. Cold Cabinets Refrigerators without freezer compartments contain 2 types of roll-bond evaporators: rear wall and U-shape evaporators, fitted at the top of the cabinet on the rear or rear and sides:

Evaporator Surface

The needed evaporator surface per cooled volume is in the following range for roll-bond evaporators: These are approximate values which can vary. To reduce for example costs for compressors and consumption of energy today often the evaporator size is increased by about 10-15 % to be able to use a smaller compressor. But this can only be finally decided by a series of tests. This sizing must be increased in the same range of the compressor's capacity increase if sub-tropical or tropical climatic conditions are selected (see chapter of refrigeration capacities).

The values are valid for roll bond evaporators. In case tubeon-sheet evaporators behind the inner liner are selected, the surface has to be increased by 10-15% if the inner liner are plastic and by 5-8% if the inner liners are metal (chest freezer or freezer compartment with metal inner walls) depending also if the tubes are fitted to the sheet with heat transmission paste or not, and on the k-values of the materials between refrigerant tube and refrigerator and freezer inside. "Cold cabinets" are normally provided with a thermostat with a constant cut-in temperature of above 0 °C so that the evaporator is defrosting only during the stand st and still period: so called "cycle defrost cabinets". With drip groove on the backside the water of the evaporator is caught and drained outside the cabinet, normally on a tray on the top of the compressor for evaporative cooling of the t he compressor.

Screening and Drip Tray Screens and drip trays are used in *- and ** star refrigerators (and the few *** star refrigerators with only one evaporator) to separate the temperature zones.


p. 49

Example for a ** star refrigerator:

Air circulation around the roll bond evaporator ensured in the typical ** star refrigerator by the distance of 25 mm between the roll bond evaporator and the inner walls. This type of models are meanwhile vanished in markets in developed countries because of icing, manual defrost work and low energy efficiency. Customers prefer *** star star models (next chapter).

What are technological the difference? *** star freezers needs compartments normally air tight separate by a door from fridge. If freezer and fridge is not air tight sealed, water from hot air from each opening of fridge will condense to ice on freezer evaporator. In areas with high humidity and stronger use evaporator will be full of ice. Ice is a very good insulator (Igloo-effect) and reduce evaporator efficiency. So manual defrosting and re-cooling of warmed up refrigerator is often needed, which also cause increased energy consumption. Energy labelling system often doesn’t reflect such customer use conditions. During use normally fridge is opened o pened at least 5 times more than the freezer. Each door opening the complete cold dry air is replaced by hot wet air. A modern fridge with back wall evaporator defrosts automatically all humidity from hot air (door opening) during compressor stop time. The fridge compartment co mpartment is bigger than the freezer compartment so that main air humidity is already automatically removed without icing as water (fridge temperature <0°C). The freezer (<-12°C or <-18°C) volume is often much smaller than the fridge with less air volume and as result less humidity inserted by hot air during freezer door do or openings. In combination with less freezer door openings as fridge door openings much lower ice needs to be defrosted in a model with sealed freezer in comparison to the described model above without air ti ght separated freezer. Suppose the freezer has 1/3 of volume of fridge and is opened in the average 5 times more frequent as the freezer, you would have 3*5=15 times less ice to be defrost as in a same model size s ize with unsealed freezer, as you have described.

5.1.5. Two-Temperature Cabinets Such ***star refrigerators or refrigerator freezer combinations use 2 evaporators, one for the freezer (< -18 °C according to ISO) and one for the refrigerator (0 °till 5°C according to ISO). The simpler ones are -like the cold cabinet-cycle defrost thermostats only switched by the refrigerator temperatures (constant cut-in temperatures above °C). The refrigerant passes first the freezer evaporator and then the refrigerator evaporator. The defrosting of the refrigerator occurs during the stand still period (cycle defrost), while the freezer is defrosted manually and not automatically. In general the evaporator of the freezer should have as much as cooled surface as possible to obtain the requested low temperatures. So normally all 5 walls of a freezer are containing evaporators (see section Tube-on-sheet or s kin evaporators). In freezers above about 60l it is recommended - and for the old DIN standard also necessary- to divide the freezer by evaporator shelves in sections of about 60l. The new ISO/EN/DIN standards (see chapter standard) are weakening this request so that such vertical freezers can now be made only by using the 5 walls for freezing (see section tube-on-sheet or skin evaporators and vertical freezers). Therefore the dimensioning of the freezers in such s uch models is very simple. But in such s uch two temperature models the


p. 50

dimensioning of the evaporator for the refrigerator is more difficult because of the interconnection between the 2 evaporators. The problem is to maintain -18 °C in the freezer without letting the refrigerator temperature falling below 0 °C, especially at lower ambient temperatures. Therefore the refrigerator evaporator is always in the range of 12-15% smaller than the one in a refrigerator of a "cold cabinet" on the same size. The final size of the refrigerator evaporator in a two temperature refrigerator or 2 door model should be tested in a air conditioned room according to the operating temperatures (for example +12 °C up to +32°C ambient temperature) requested on the market. A two temperature refrigerator only thermostatically controlled by the refrigerator will not start freezing in lower temperature environment even if the freezer temperature goes above -18°C. These 2 problems have caused tremendous costs for example for Liebherr in their Chinese project in DXINGDAO, to replace their construction to the conditions that Chinese use refrigerators in cold ambient temperatures in the winter time, not foreseen in such refrigerator constructions.

Connections of Refrigerator and Freezer Evaporators in Series There exist following connection possibilities of the evaporators in 2 temperature refrigerators, but the version with roll-bond (see picture) is history, practically no one anymore in use for cost reasons. After developing tube-on-sheet (TOP) evaporators (see next chapter) for the refrigerator compartment and even for smaller and medium size freezer compartments there are other combination possibilities of the freezer and refrigerator evaporator, which are cheaper and better. But to use one compressor for cooling 2 different temperature zones the 2 evaporators have to be connected and there sizes dimensioned according to the temperatures to be reached and the sizing optimized in tests. Tubes are normally connected by brazing with silver alloy .

An alternative, which for cost reasons is seldom used, is Lockring tube joint method, which costs in the range of € 0.50 per joining ring. Hydraulic Press Lockring Assembly before and after Pressing

The problem with brazing (as well as the use of the Lockring system) is the Aluminium coated tubes. Aluminium coating must be removed completely in both cases to avoid leakage. Tubes have to be delivered with one end extended or have to be extended on one side locally which is difficult.


p. 51

5.2. Tube-on-Sheet, TOP or Skin Evaporators For cost reasons expensive roll-bond evaporators are more and more vanished nowadays. But also quality reasons like -

longer lasting of aluminised steel tubes in comparison co mparison to roll-bond better defined cross sections in a tube in comparison co mparison to roll-bond

were important. Not painted or otherwise protected aluminium tubes could be damaged by the Hydrochloric acid inside foam. Roll bond channels not only in bending areas have partially reduced cross section with partial internal pressure press ure increase (heating) of the evaporator. Especially by using R134a as refrigerant this effect can happen because such a gas does not separate completely from the ester oil so that small quantities of ester oil will pass the circuit. Skin evaporators use the refrigerator or freezer inside wall as evaporator. The first application in which such evaporators were introduced were chest freezers, but in principle all aluminium roll-bond can be replaced by such tube-on-sheet evaporators, TOP or skin evaporators named evaporators, but in practice not in all cases it is recommend and cheaper. Still in some few applications, like some freezers, which have to be cooled from inside and not only by the walls roll-bond remains as technical solution.

5.2.1. Chest Freezer Evaporators Chest freezer inner liners are normally made today out of aluminium sheets and behind the aluminium sheets you have zinc coated steel or aluminium tubes and PE foil. The aluminium tubes can also be painted to protect it against Hydrochloric acid (HCl) which is always a little bit inside PUR foam, but for zinc coated steel tubes the foil is sufficient and it is the cheapest solution with the best quality after copper tubes:

Chest freezer - tube-on-aluminium-sheet-evaporator All the 4 side walls of the chest freezer are used as evaporators. In case of the expensive aluminium roll-bond evaporators there is a difference of 2 K between the evaporator surface and the air temperature in the chest. Today the Kvalues with tube-on-sheet evaporators are less than 5K. But today Zink coated steel tubes are more in use (see underneath).

Chest Freezer Pull-Down Test Several chest freezers show following average values during a pull-down test with big loads. According to DIN 8953 or ISO 5155 the pull-down test will be made by 25 kg Tylose parcels per 100l chest volume. The chest freezers should reach following sequences of the evaporating temperatures. In the new standard 25 °C is used while in the old standard 32°C ambient temperatures were used. E V A P O RA T I N G T E M P E R A TU R E Ambient Temperature Maximum

32°C 25°C

-10°C -13°C

During crystallisation

At stationary conditions

-21°C -24°C

-31.5°C -33.5°C


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We can use this test and these values for a pull-down test to find out if a new developed chest freezer is suitable or need to be changed. The ISO and DIN standard also prescribes a pull-down test with smaller loads to determine the freezing capacity of the model (See standards). The distance between the evaporator coils and and the mode of fixing is important; 85mm is a suitable distance between the tubes tubes as well as a maximum of 40 mm from fro m the upper and lower edges to the evaporator’s coils.

Chest Freezer Evaporator Tube Length The tube length of the evaporators coils are described in the following table: An 5/16 inch (8mm) tube is normally used up to 28 m length, - above it will cause too much pressure drops- and and 3/8 inches (10mm) tube is used for larger tube lengths. The most favourable evaporator coil design for chest freezers in the spiral with the inlet at the top and the outlet on the bottom. Delicate are the corners: Any cross section reduction should be avoided on these corners. For these reasons some manufacturers use evaporators coils divided in 4 sections, but the first variation is better if reduction on cross sections can be avoided (see drawing with corner section beginning of this chapter). Today the tubes are not anymore copper for price reasons. Aluminium tubes need aluminium inner liners while aluminised or zinc coated steel tubes (or copper plated steel tubes) should get enamelled steel inner liners or aluminium sheets. s heets. Aluminium tubes need butt-welded copper joints (protected against corrosion by a coat of PVC or enamel) to connect it to the copper or steel heat exchanger. The tubes are fixed by tapes. In case of poor contact between the tube and the inner liner sheet it is necessary either to increase the length of the evaporator coil or to use contact compound (Terolan with Lambda 0,6W/m °k or thermal mastic with Lambda 0,8W/m°C). The coil must be protected by a Polyethylene foil to avoid that foam can be inserted between the tube and the inner liner and also to protect the aluminium tube against Hydrochloric acid which is in small quantities inside the foam in case Aluminium tubes are used.

Working Processes to mount chest freezer evaporators of Aluminium or copper tubes Version with Aluminium or copper tube winding machines:

1. Mounting Aluminium Sheets on a core 2. Winding Aluminium or copper tubes around the core 3. Fixing tube by scotch tape 4. Protecting evaporator by PE foil of 0.08mm Steel Tube Evaporators in 2 versions. Better quality with a much longer lifetime as with aluminium tubes can be reached if zinc coated steel tubes or even aluminium-zinc coated steel tubes are used (see drawing at beginning of this chapter). No doubt the best would be copper tubes, but copper tubes are very expensive. Zinc coated tubes cannot rust as long as the freezer is running and the tubes under low temperatures. But if there are periods, that the freezer are not used, zinc coated steel will rust. To avoid even in this time any rust aluminium-zinc coated steel tubes for refrigerator evaporators with temperatures above 0 °C can be used. Such aluminium zinc coated tubes also reduce thermo-element effects to the Aluminium sheet. To avoid even in this time any rust aluminium-zinc coated steel tubes for refrigerator evaporators with temperatures above 0 °C can be used. Such aluminium zinc coated tubes also reduce thermo-element effects to the Aluminium sheet.


p. 53

Disadvantage of this tubes are the more difficult manufacturing process of steel tube evaporators. Either the tubes are pre-bent on a special machine to be placed on the liners horizontally with tubes as made like on the last picture and drawing or purchased and mounted by hand. Also such serpentines (see picture beside) can be used. The flat serpentines can be bent by hand round the chest liner by turning a tube by 90 ° on a corner position:

5.2.2. Cold Cabinet Evaporators For refrigerator without a freezer compartment such a tube-on-sheet, TOP (=tube-on-plate) or skin evaporator can be used instead of roll-bond for cost and quality reasons- either tube on flat aluminium foil. This is a high energy efficient version. The vertical loop prevents that liquid refrigerant can come into the suction and destroy the compressor an accumulator is not needed. Furthermore the flatted tube improves the heat exchange and reduces that ice can be built up between tube and Aluminium sheet: Variability of overall dimension:

A = 250-450 mm B = (n-1) x p P = 42 or 50 mm N = 6 -16 as required.

Flatted Evaporator tube:


p. 54

In such models the liquid refrigerant enters directly into the refrigerator evaporator and could pass liquid into the compressor if there is no accumulator between. Accumulators today are removed to increase efficiencies (class A-models). To avoid that liquid refrigerant can return through the suction tube into the compressor, which could destroy the compressor, the vertical bend is made. Today’s most used evaporator version for cold cabinets without freezer.

There are different ways of connecting the evaporator tubes and Aluminium sheet or foil to the inner liner Version with roll formed sheet is too expensive is the solution to insert tubes into a roll formed aluminium sheet (drawing right side).

Also a double adhesive tape (€1,50-1,70/m²) is much more expensive as a hot melt glue (Teroson (Ter oson €7/kg 80g/m²) applied on aluminium sheet and cold pressed on the liner so that a hot melt roller press investment amortize inside 1 year if more than 2500000-300000 refrigerators are produced in a year. Today - especially in countries with higher salaries - an adhesive Aluminium foil is most used (see its specification in next chapter 2 -Door Refrigerators).

5.2.3. Evaporators of one Door Refrigerators with Freezer Compartment Capillary

Evaporators of one Door ** Refrigerator Traditionally a refrigerator with up to 2 star ** freezer compartment or ice tray has a roll bond evaporator inside the refrigerator with a tray for condensed water and for screening (see Chapter 5.1.4). These are more ice makers than refrigerators and consume too much energy and should be stopped in production. All the wet hot air from each door opening are converted to ice on the evaporator, which can be avoided by a 3 star *** model. There exist few tube-sheet-evaporator models on the market made out of aluminized steel tubes of 6-8mm dia. On single adhesive aluminium foils covered by 0.08 mm ethylene foil (see next page) in the following follo wing way:

Freezer Evaporator

Refrigerator Evaporator Subcooling Heat Exchanger

The food liner will be formed with a tilted freezer block during thermoforming to allow sheet material to be inserted between freezer and refrigerator compartment.


p. 55

Evaporators of one Door *** Refrigerator A refrigerator with good isolated *** star freezer compartment can be made with tubes-on-sheet-evaporators in the following way: Bending points The tube distances are between 4050mm for a tube of 5/16inch (=8mm dia).

To the Evaporator of the refrigerator box.

To the capillary tube -

Flat serpentine Evaporator for freezer box of a 12 cu.ft Two-Door refrigerator, Tube: Single wall O.D. 8 x 0.7 mm hot-dip zinc coated

5.2.4. Two Door Refrigerator Evaporator in the Refrigerator compartment Between inner liner and foam a tube-on-aluminium-sheet evaporator can be installed: The tube can be copper, aluminium or aluminium coated steel tubes with 6.35mm round or 8mm pressed to oval tubes. Zinc coated steel can not be used because of corrosion (wet air in time of manufacturing will condense on tube; tubes are not permanently frozen because of plus temperatures in the refrigerator, so a zinc coated tube can corrode). So called Tube-on-Sheet-Evaporator or TOP (=Tube-on-Plate) Evaporator.

st

1 solution: Roll formed aluminium sheet evaporator with aluminium coated steel tubes

One of the first solutions developed was to have aluminium roll formed to enter tube inside channels (drawings), but under cost aspects it is not recommended. Second solution was to use a double adhesive tape

(€ 1,4-1,6/m²) between Aluminium sheet and inner liner. But also t his vanishes meanwhile for cost reasons and was first replaced by aluminium sheet made adhesive with hot melt glue (Teroson Q5707). 3

rd

Solution: Roller machine for hot melt glue on aluminium sheets


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4th Solution: Adhesive Aluminium foils TOP evaporator.

Most used version today is adhesive Aluminium foils on tubes evaporator. Especially in countries with higher wages it is cheapest and therefore most used, as this can be done automatically. Transfair can provide a video of such machines.

Working Process to mount Tube-on-Sheet or Skin Evaporators In the past such adhesive aluminium sheets and round tubes were used (see picture). But today we use adhesive aluminium foils and flatted tubes. The adhesive Aluminium foil TOP evaporator are made as following: with spenders with Aluminium foil rolls, cut in length according to models are placed near the cabinet preassembly to facilitate mounting.

Surface of Tube-on-Sheet (=TOP) Evaporators. The surface of tube on sheet evaporator is a little bit bigger (10-20%) than roll bond (see graphic of chapter 5.1.4.) because of larger pitch of 60 mm, but the procession is much simpler and cheaper. There is no need of painting and no special copper/aluminium joints are necessary, if steel tubes are selected. The adhesive Aluminium and PE foils should be pressed cold by a roller press with 4,5kp/cm². Transfair regularly supplies such evaporator roller press and can grant the production know how.

Freezer Part inside 2-Door Model Up to 60l freezer. A freezer up to 60l does not need inside the

freezer compartment cooling evaporators; cooling from the wall (behind the inner liner) is sufficient.

In this case the same construction of tube-on-sheet evaporator like the freezer compartment as previously mentioned for the one door model can be used or the following construction: The surface of tubes is always frozen (-24 °C), so that aluminium coating is not needed and zinc coating is sufficient, but in case such a system is not always running an aluminium coating is better.


p. 57

Freezers above 60l. A freezer of 60l and above cannot be cooled from the walls of the inner

liner if the old still valid DIN standards are applied. 1-3 evaporator trays are needed inside the freezer. Few existing tube-on-sheet solution for this (Zanussi) do not look as nice as roll bond evaporators and the investment on machines is very high.

Depending from each model itself and the cost of the components and processing mixed solution could be in some cases useful. Theoretically there should be nice solutions. But all solutions for vertical freezers really made till now according to the old DIN standard we can not recommend for smaller scale production, because of high investment costs. Therefore in this area roll bond is still better. To connect the roll bond evaporator tube by brazing special Aluminium Copper joint made by pulsed electrical induction are needed, which can be purchased. Even the a.m. Lockrings allow direct connection of the Aluminium tube to the steel or copper tube in the circuit. Freezers have the highest temperature at the top of the cabinet. To improve the freezer quality often the top evaporator coil are doubled or of a larger size; or higher number of wires or 2mm wires instead of 1,5 mm wires wires are used. A Tube-on-plate evaporator with 50mm spacing between the tubes has approximate a value of 6,9 W/m²** °K. The connection to the tubes is reached by some flanges of the plate being bent Tube-on-plate freezer evaporator.

round the evaporator coil.

Wire-on-tube evaporator.

freezer

A wire-ontube freezer evaporator with tube coil spacing of 6080mm and 1,5mm wires in distance of 10mm at both sides reaches a Lambda value of 8,5W/m²** °K.

Tube-on-Plate Freezer Evaporator

Wire-on-Tube Freezer Evaporator

Transfair Engineering: Designing and Prototyping Prototypin g of Refrigerator … Cooling Circuits. 5.5 Evaporator, No Frost Damper Thermostat, Tandem System

p. 58

Single evaporators are connected in series. A circuit with inlet in the upper section and outlet in the lower section should be selected. Evaporators in series.

Evaporator and condenser in tube version see page 32-34.

5.2.5. Skin versus Roll-Bond Evaporators The roll bond evaporator still has the highest Lambda value of approximate 10.2 W/m²** °K. Major advantage for tube on sheet evaporators is the lower cost as you need only - tubes (for making the serpentine locally) or tubes serpentine, - aluminium sheets or foils, and - PE foils and no expensive roll bond evaporators.

Cost comparison.

Roll bond have to be painted, tube-on-sheet evaporators not. To connect evaporator to steel, no special aluminium copper joints are needed. Steel tubes can be easier welded, but need better bending tools than the roll bond. Processing and Painting.

Instead of costly roll bond or already bent serpentine simple tubes can be used and cut and bent locally by special tube cutting and bending machines (line costs about USD 370,000.00 for 33 0,000 pieces per year in one shift). The inner liners should not be thicker than 2.5mm to avoid isolation between evaporator and refrigerator or freezer so that only modern thermoformers should be used. This T his also reduces the cost of material. Till today aluminium tube-on-sheet solutions are not as nice from the surface as roll bond. Therefore they are mainly used behind the inner liner, which has the advantage that you can clean easier the refrigerator or freezer. If you need evaporator inside the cabinet to be seen (large freezer, one door refrigerator with ice tray) roll bond is still recommended.

Aesthetic aspect.

Aluminium coated steel tubes have less corrosion than roll bond especially if you take into consideration mechanical stresses on surface and acidic areas. If you would place the roll bond behind the inner liner it still can not compete because PU foam contains Hydrochloric acid which will hurt unpainted aluminium tubes more than aluminium coated steel tubes (Al/Fe layer is more resistant against corrosion than Al or Fe alone). Corrosion and services.

In case of wrong processing of braze or Lockring connection of tube on sheet condenser behind the inner liner, repairing is impossible. Therefore all connections should be made outside the foam to be able to repair it if one time it will really be needed


p. 59

which is very seldom. The failure rate on-tube-on-sheet-evaporators behind the inner liner is much lower than with any roll bond evaporator solution. Overall because of costs, European refrigerator producers have already replaced roll bond in a.m. cases by skin or tube-on-sheetevaporators with the effect that the mayor European roll bond production were closed down. But the mayor advantage - beside of costs - are the improvement of cross sections reachable with evaporator tubes instead of roll bond channels. Tubes do not have any reductions in bending areas which is very important for the performance efficiency especially if R134a or R600a as refrigerants are used.

Cross section.

5.3. Optimisation of Evaporators 5.3.1. Evaporator Channels or Tubes and their Cross Sections Since 1991 the R 12 refrigerant is replaced by R 134a refrigerant and size 1994 R134a refrigerant mainly in Europe is more and more replaced by R600a. Both need an improvement of the channels and cross sections in comparison to R12 systems. s ystems. In general for all refrigerants optimised cross sections of channels improve strongly the efficiency. There exist for each compressor displacement and system design an optimum size of the channel cross section, depending on the discharge of the compressor and the length of the tubes or channels. If it is too small, the pressure drops too much across the evaporator with the result that the compressor capacity cannot be completely utilised. If the cross section is i s too large the speed of the refrigerant – optimal at 4-5m/sec - becomes to low and oil can accumulated in the evaporator with the effect that the evaporative capacity reduces. Such accumulation of oil can even put the oil pumps in the compressor out of order. This effect can be increased by the use of R134a which does not separate as well as the R12 between gas and oil so that ester oil can pass the whole refrigeration circuit. Therefore any reduction of the cross section or pockets in which the oil can be accumulated must be avoided in HCF-134a systems much more than in CFC-12 systems. Cross section and efficiency.

5.3.2. Speed of refrigerant and Pressure Drop Speed of refrigerant.

avoided.

The speed of the refrigerant should be in the range of 4-5m/sec. By this speed oil accumulation will be

In R600a systems performance reductions because of pressure drops are even worse because of the lower absolute pressure of R600a. Therefore the tube diameter to receive a refrigerant speed of about 4-5m/sec and any reduction of cross sections should be avoided. This was one of the reasons - beside of cost reductions - why roll bond evaporators which can have variable cross sections because of their way of manufacturing and which can have smaller cross sections in the bending area were replaced by tube-on sheet evaporators with always correct cross sections. Pressure drops on evaporators can be measured: the temperature difference in a stable system (not during the pull down) between the evaporator inlet and outlet should be in the range of 1 °K. If it is larger it should be checked if their are reduced cross section, if not the diameter must be step by step increased till the temperature difference between inlet and outlet is in the range of 1 °K, but do not increase the diameter more than needed to avoid pressure drops to avoid speed reduction on the circuit caused by to big tubes. Measurement of pressure drops.

5.3.3. Liquid-Gas Separator and Accumulator A small vessel for example made from a tube t ube with higher diameter as the evaporator tube can be used as gas-liquid separator to make sure that no liquid comes into suction s uction tube and compressor and could damage compressor. Such a vessel also works as accumulator to allow cooling circuit to work more efficient under a much wider range of temperature and refrigerator/freezer load fluctuation, without increasing the evaporator tube, so such an accumulator also allows refrigerator evaporator size and


p. 60

evaporator tube lengths reduction, without sucking liquid into compressor, which would happen, if the evaporator size would be reduced without an accumulator. In past it was used only in chest freezers and upright freezers, but seldom seldo m in fridge-freezers. Such accumulator even allow to charge slightly more refrigerant, without reducing coefficient of performance, so the cooling system could tolerate even small leaks near 1g/a and by this t his slightly overcharging, without reducing superheat (+3-4°K), in this case it will increase lifetime of such small leaking refrigerator, but only only if leak is really small. Modern high efficient fridge-freezer combinations with low energy consumption ( A and A+ models) are often quite slow in pulldown of the refrigerator temperature cause by a quite long fridge evaporator tube length. Using an accumulator allow to shortening of evaporator tube length and size of fridge evapor ator by 15-20% it increases the speed of refrigerator pull down time. So this accumulator is an instrument to compensate this bad side effect of energy saving effort s, which in past often slow down refrigerator compartment cooling.

5.4. Sizes of Upright Freezer Evaporators Per 100l cabinet volume a 0,6 m² evaporator surface and wire-on-tube-evaporators are suitable, while tube-on-sheet evaporators need about 20-25% higher surfaces per 100l volume. The difference between the cabinet temperature and the evaporator coil temperature should not exceed 5 K.

5.4.1. Pull-Down Test of Vertical Freezers To check if the evaporator on a freezer system is suitable we make the pull-down test already described for a chest freezer test. A pull down should be made at 32 °C ambient temperature with a load of 25kg Tylose parcels per 100l volume. Following average values for a number of upright freezers are reached during the various stages of the evaporating temperature during freezing: EVAPORATING TEMPERATURE Ambient Temperature Maximum During crystallisation


32°C 25°C

-31.5°C -33.5°C

-10°C -13°C

-21°C -24°C

The evaporator surface calculations were already made previously. The tube diameter and length should be selected in the following way: 5/16 inch (=8mm) dia are often used for evaporator coils up to 26 m; 3/8 inch (=10mm) should be used for longer tubes to avoid strong pressure drops and poorer utilisation of the compressor capacity. Roll bond evaporators with 22 mm cross sections used in upright freezers with a volume up to 400l should use 2 parallel flows via 2 channels and above even more parallel channels. To avoid that the frosting up of the evaporator will destroy the freezer door, the evaporator should have a distance to the door of 20-30mm. Because of the reduction of the standard demand (DIN 8953) on the pull-down capacity of a vertical freezer in comparison to previous demands, it is possible today to use only the inner cabinet as evaporator to achieve the standard and no additional evaporator shelves inside the freezer ar e needed:


5.5.

p. 61

NO FROST Evaporators

No frost design separates the evaporator from the storage space and removes from time to time automatically the frosting from the evaporator finned coil by heat so no frost are visible inside the cabinet. Such system exists for 2 temperature cabinets and for freezers. A fan is used to draw the warm air from the storage space across a finned coil evaporator and back to the storage. The defrosting of the coil is made automatically by electrical heaters and controlled by a timer. During opening of doors the fan stops. In a HC-600a or HC-290 design the electrics must be “N” protected or outside the reach of a leak (see chapter 8.); the heater surface temperature should not go above 350°C (underneath the ignition temperature of HC-600a, which can be reached by limiting the electric heating power per surface to 1,5W/cm² by resistance wire and limiters. furthermore the electric terminals should should be outside the R600a leaking area (or with special fixings see chapter 8.3.1.). IR heaters cannot be used.

5.5.1. Surface of Fins and Air Charge Following surfaces are needed for No-Frost cabinets: For a two temperature cabinet a surface of 0,4 to 0,45 m² per 100l cabinet volume is suitable for subtropical areas. For upright freezers it will be approximately 0,5 m² per 100l freezer volume for the same conditions. These sizes apply for a charge of air of about 100m³/h.

5.5.2. Tube Size and Fin Distance Normally the finned coil evaporator for such appliances has 3/8 inch (10mm) tubes and the K-value at natural air circulation is at 8W/m² x °K and at forced air circulation at 14 W/m² x °K as long as it is not frosted up. The fin distances are not lower than 5 mm to avoid reduction of air pressure. In addition the distance of fin at the air inlet is often double as much as at the outlet to avoid too much reduction of the air pressure.

5.5.3. Defrosting The frosting up is much faster than in a normal freezer evaporator; therefore such systems need 3 or 4 times per 24 hours defrosting. A special timer to start and stop automatically every 6-8h the defrosting heater for some minutes is needed inside a No-frost model. This heater is passing the finned coil. Heating up of coil evaporators to remove 3-4 times per day is the main reason why No-frost models increase energy consumption, but it can be limited by some tricks (chapter 9.4.1). In case of HC-600a or HC-290 the surface temperature of the heater should never go above 350°C. This could be easily realized by electric resistance heaters limiting the electric heating power per surface to 1,5W/cm² and additional limiters, but not with IR heaters (see chapter 8.3.9.).


p. 62

5.5.4. Air Ducts of NO FROST Refrigerators A lot of efforts in the design of NO FROST models are made in the air ducts of 2 temperatures models to distribute the quantity of cold air between the 2 sections in right proportions; the freezer normally needs much more.

5.5.5. Dumper Thermostat Good systems have a second thermostat constructed as a damper so that the air flow between the 2 sections and the 2 temperatures between the refrigerator and freezer can vary according to the real needs. This reduces energy consumption. In case of R600a or R290 models a sparking thermostat switch must be sealed by box (minimum IP54 if gas cannot acumulate in this area (see chapter 8. 3.11.) or placed outside leaking area of HC-gas.


p. 63

5.5.6. Tandem System Tandem system is an advance refrigeration cycle approach using 2 no frost evaporators in 2 temperature zones in refrigerator/freezer system. It was developed by K. Kim, B. Kopko and R. Rademacher, University of Maryland/USA and is used by Samsung/Korea. Such a tandem system takes advantage of transient operations, allows defrosting without electrical heaters by using the thermosiphon phenomenon between the 2 evaporators. With a sophisticated electronic control the temperature of each compartment can be controlled independently and the energy consumption can be significantly reduced in comparison to conventional No-Frost refrigerators, which is the main advantage. For example for a large 18 cuft 2 door No-Frost model using such technology 18% savings could be reached in comparison to conventional No frost models of the same size by applying the American Standard for energy consumption. Refrigeration Circuit Scheme

Electrical Scheme

For further details see: K.Kim, B. Kopco and R. Rademacher: Experimental Research and Development of Tandem System Domestic Refrigerator. Department of Mechanical Engineering. Center for Environment Energy Engineering. University of Maryland. College Park MD 20742.

Transfair Engineering: Engineering: Designing … Cooling Circuits. 5.6. Evaporator, Evaporator Tests, Pressure Drop Test, Temperature Distribution, Pull-Down Pull-Down Test p. 64

5.6. Fridge Ventilators Today not only No Frost models, even some so me good defrost models have ventilators.

-

Traditional fridges have different temperature zones with lower temperature in lower areas, so that fresh meat should s hould be positioned on lowest tray etc. They reach about 5°C refrigerator temperature during run though the fridge b ack wall surface temperature is < -7°C (if like in i n Europe on standard fridges the evaporator is mounted behind this wall). A ventilator distributes the air so that maximum 1°C temperature exists. Under same conditions (food load and environmental temperature, door opening times) the ventilation in comparison to conventional model has following advantages: - Ventilation reaches lower set temperature to switch off compressor in about half of time and - the cooling down after door opening is nearly double as fast, with effects on - Longer storage time of food, - Less energy consumption and costs of cooling down (less time for compressor run), which is much more than electric consumption of ventilator itself (~1W), or - 3°C lower fridge temperature (2°C instead of 5°C), if the compressor would run same time with same energy consumption. The fresh goods can be positioned anywhere.

-

The beverage cooling time would reduce to half .

Ventilation in fridge.

Warm air contains more humidity as cold air. Such warm air humidity entering during fridge door opening condensate to water drops, mainly to cold backside wall, but also on already cold foods which in case of cheese and sausage sa usage can reduce their storage time. By ventilation this water drops on o n fresh food would be reduced. Too strong stro ng ventilation of fruits and vegetables would dry them. So they should be stored inside separate not ventilated area like inside a vegetable vegetable crisper or box.

5.7. Evaporator Tests The efficiency of heat exchange of evaporators can be measured like condensers with calorimeters. Also comparison test with hot water is possible (see chapter 3.6). But normally the evaporators are tested already mounted on a refrigerator system by following tests:

5.7.1. Pressure Drop Tests There is an optimum concerning size of the channel cross section and total length of tubes the refrigerant has to pass in the evaporator or evaporators made in series in a multi temperature system. If the cross section is too small for the total length of the evaporator(s), the pressure drops too much across the evaporator(s) with the result that the compressor capacity cannot be completely utilised. If the cross section is too large in comparison to the length of evaporator tube to be crossed the speed of the refrigerant becomes to low and oil can accumulate in the evaporator with the effect that the evaporative capacity reduces. Such accumulation of oil can even put the oil pumps in the compressor out of order. The speed of the refrigerant should be in the range of 4-5m/sec. By this speed oil accumulation will be avoided. Pressure drops on evaporators can be measured: the temperature difference in a stable system (not duri ng pull down) between the evaporator inlet and outlet should be in the range of 1 °K. If multiple evaporator systems are measured such difference of 1 °K can be accepted for each evaporator.

Transfair Engineering: Designing … Circuits. Circuits . 5.6. Evaporator, Evaporator Tests, Pressure Drop Tests, Temperatu Temperature re Distribution, Distributi on, Pull-Down Tests

p. 65

5.7.2. Measurement of Temperature Distribution in MultiEvaporator Systems with one Control Multi temperature cabinets with one or more evaporators have to reach defined temperatures in each zone. I f only one circuit and one temperature control exist the temperature distribution in different environments and loads should be tested to control if the selected different sizes of evaporators in the different zones and/or the screening between the zones are correct made. Each compartment should reach the temperature values according to the standards and climate classes as described in Chapter 1.3.

5.7.3. Pull Down Tests A pull down should be made at 32 °C ambient temperature with a load of 25kg Tylose parcels per 100l volume. Following average values for a number of upright freezers are reached during the various stages of the evaporating temperature during freezing: Vertical freezer pull down test.

Ambient Temperature

Maximum



32°C

-10°C

-21°C

-31.5°C

25°C

-13°C

-24°C

-33.5°C

Several chest freezers show following average values during a pull-down test with big loads. According to DIN 8953 or ISO 5155 the pull-down test will be made by 25 kg Tylose parcels per 100l chest volume. The chest freezers should reach following sequences of the evaporating temperatures . In the new standard 25 °C is used while in the old standard 32°C ambient temperatures were used. Chest freezer pull down test.

Ambient Temperature

Maximum



32°C 25°C

-10°C -13°C

-21°C -24°C

-31.5°C -33.5°C

Pull down test for fridge-freezers and cabinets with or without freezer compartment.

should be reached according to the valid standards:

Following values of the evaporator

Climate

Ambient temperature

Cabinet temperatures

Max. temperature in freezer compartment (inside test packs)

SN

10-32°C

t3
*

N

16-32°C

t3
** -12°C

ST

18-38°C

t3
*** -18°C

T

18-43°C

-1°C
t3
**** -18°C and defined freezing capacity

- 6°C

t1, t2 and t3 are mean temperatures for top, middle and bottom measured in copper cylinders. tm is the mean temperature of t 1, t2 and t3 . Four star cabinets

three-way valve.

with large freezing sections normally have 2 independent systems or one system with separated control by a

More detailed description how such pull down tests have to be executed are described in the ISO standard 5502 (in past ISO 7371, ISO 5155, ISO 8187) which we will not repeat here.

Transfair Engineering: Designing … Circuits. Circuits . 5.6. Evaporator, Evaporator Tests, Pressure Drop Tests, Temperatu Temperature re Distribution, Distributi on, Pull-Down Tests

p. 66

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator Refrigerator and Freezer Cooling Circuits. 6. Dryer/Desiccant, Dryer/Desiccant, types, Standards and Tests

6.

DRYER/DESSICANT

6.1.

Filter Dryer characteristic

The requests on dryers

for R600a did not change to the ones for sizes of 4 Angstrom like 4A-XH-5 of Union Carbide is used in

R600a.

For HFC134a

p. 67

R12 systems. As a desiccant a molecular sleeve with pore household refrigerators and freezers working with R12 and

refrigerant systems more efficient dryers with following follo wing desiccants are required:

which also can be used for R600a. In this case the molecular sleeve has pore sizes of 3 Angstrom. So also other dryers with desiccant using 3A molecular sleeve pores, like Siliporite H3R (CECA) can be used. XH-7 or XH-9 (UOP-Union Carbide)

In general the dryer should be selected in a way that the hygroscopic percentage level of a dryer is below 4% after operating the system and that the moisture level of the t he dryer remains below 10mg. The dryer's volume in case of HC-600a models remains the same as for the same CFC-12 model. For HFC-134a models the desiccant volume should be increased by about 20% in comparison to R12 dryer's volume in the same model. The total household refrigerator system should not contain more than 150mg moisture. To improve the quality of the refrigerator, especially in humid climate, to speed up evacuation, to remove moisture on high and low pressure sides of the cooling system a filter dryer with a third 6mm tube is recommended to evacuate on both sides of the circuit parallel. It is very important for R134a and for R600a refrigerators to dry the evaporators and condensers before assembly by dry air or dry nitrogen with dew point <-50°C. Furthermore is quality wise important to open the filter dryer and compressor, specially the R134a compressor with hydroscopic hydroscopic ester oil, last moments before cooling circuit circuit brazing to prevent entry of humidity. Even under these precautions we still have regularly 2 sources o f humidity -

the refrigerant and the compressor oil,

which both should be controlled with humidity measurement regularly.


6.2.

p. 68

Refrigerant Dryer Test Standards and Methods

Following standards to test filter dryers can be applied: DIN 8949 (2000): Refrigerant filter driers - Testing

ANSI/ASHRAE Standard 35 (1992) : Desiccants for Refrigerant Drying, Method of Testing.

Method of Testing Liquid Line Refrigerant Driers. It prescribes test methods for determining flow capacity and water capacity performance characteristics of liquid line refri gerant driers. It applies to driers that employ a desiccant. The water capacity test method prescribed can be used to test a dr ier either "as received" or after being reactivated in accordance with manufacturer's recommendations. Dual units of measurement. ANSI/ASHRAE Standard 63.2 (1996): Method of Testing Liquid Line Filter-Drier Filtration Capability. It prescribes a laboratory test method for evaluating the filtration capability of filters and filter-driers used in liquid lines of refrigeration systems. ANSI/ASHRAE Standard 63.1 (1995) (RA 2001):

Method of Testing Flow Capacity of Suction Line Filters and Filter-Driers. It establishes a method for measuring the flow capacity of refrigerant suction line filters and filterdriers. Intended for use on both sealed model and replaceable element type suction line filters and filter-driers of all types. Dual units of measurement. ANSI/ASHRAE Standard 78 (1985) (RA 2003):

ARI STANDARD 710:86 Absorption Capacity of dryers

It is useful to received from manufacturer of filter dryer corformity declaration to these standards and capability test results.


p. 69

Transfair Engineering: Engineering: Designing …Cooling Circuits. 7. Refrigerants, Thermal Characteristics; COP, Volume Capacities, Pressure Diff./Ratios, Superheat Superheat p. 70

7. REFRIGERANT Today the selection of refrigerant depends on following follo wing aspects: - environmental aspects (phasing our of CFC's like CFC 12) - high energetic efficiency - non toxicity - chemical stability in use - compatibility to other materials in use and last not least - costs and availability. REFRIGERANTS

Dichlordifluormethan Propylene Propane Propadiene Cyclo-Propane Tetrafluorethan

Formula

R12 R1270 R290 R1250 RC270 R134a

Dimethylether

E170

Isobutane

R600a

Butene Butane

R600

Mol weight

Tnbp

Tcrit

Pcrit

[kg/kmol]

[°C]

[°C]

[bar]

CCl2F2 C3H6 C3H8 C3H4 C3H6

120,93 42,081 44,094 40,065 42,081

-29,8 -47,6 -42,0 -34,4 -32,8

112,0 91,8 96,7 119,9 124,7

41,2 46,0 42,5 54,7 54,9

C2H2F4

102,030

-26,4

101,1

-11,7

135,1

C2H6O C4H10

C4H8 C4H10

46,069

58,124

56,108 58,124

-24,8 - 6,2 - 0,4

126,9 146,5 152,1

40,6

52,4 36,5

40,2 38,0

At moment only 2 CFC free refrigerants are used in the refrigerator household appliances - HFC-134 a (tetrafluorethane) and - HC-600a (Isobutane).

Propane HC-290 which has also an excellent efficiency is not used in the household as it works under higher pressure which causes a higher noise and shorter lifetime for the compressors. Also the mixtures of propane and Isobutane (the so called Dortmunder mixture, invented by Prof. Rosin) and first used by the company Foron upon recommendation of Greenpeace, is now more and more vanished from the market in developed countries for noise reasons, problems of lifetime and in some cases efficiency problems caused by the temperature glide of condensation and evaporation; but it could be possible that it will have success in developing countries, specially in retrofitting of existing appliances if the retrofitted system can pass safety tests needed for using inflammable refrigerant or as replacement of R12 in R12 compressors because the thermodynamic behaviour (displacement volume) is similar to the one of R12 and so no mayor change in designs of the compressor or other circuit components – except electrics are needed. We concentrate on the development of new appliances and therefore on HFC-134a and HC-600a as refrigerants.

7.1. Thermodynamic Characteristics of Different Refrigerants A good refrigerant for household appliances should be able to condense under not too high pressure at 40 °C and to evaporate at -25°C. The superheat should be at 30 °C and it should be possible to use an internal heat exchanger if needed. In the following the most important data of o f refrigerants are compared to the ones of R12:


7.1.1. Efficiencies Following refrigeration efficiencies (COP-coefficient of performance) can be reached in comparison to the one o f R12:

7.1.2. Volumetric Capacities Following refrigerant volumes have to be displaced by the sy stem in comparison to the R12:


7.1.3. Pressure Differences Following pressure differences between the high isobaric pressure on the condenser and the low isobaric pressure on the evaporator are reached by the different refrigerants:

7.1.4. Pressure Ratios The pressure ratio between the condenser and evaporator pressure is in the following range:

7.1.5. Suction Pressure The suction pressure at the starting of o f the compression process reaches following values at different evaporating temperatures for the different refrigerants:


7.1.6. Superheat The superheat (=enthalpy difference between the compressor suction and the evaporator saturated vapour conditions) for the different refrigerants reaches following values:

7.1.7-9. Pressure Enthalpy Diagrams of R134a, R600a and R290 The 3 important refrigerants as used for new appliances have following pressure enthalpy diagram (Mollier-h, lg pdiagram).

Transfair Engineering: Designing …Cooling Circuits. 7. Refrigerant, R134a Pressure-Enthalpy Diagrams

_

p. 74

Transfair Engineering: Engineering: Designing …Cooling Circuits. 7. Refrigerant, R600a Pressure-Enthalpy Pressure-Enthalpy Diagrams _

p. 75

Transfair Engineering: Engineering: Designing …Cooling Circuits. 7. Refrigerant, R270/R600a Pressure-Enthalpy Pressure-Enthalpy Diagrams (Care 30)

p. 76

Transfair Engineering: Engineering: Designing …Circuits. …Circuits. 7.2 Refrigerant, Working Working with with R600a, Purity Purity and Cleanliness, Cleanliness, Flammability and Hazardous Hazardous Situations

p. 77

7.2. Purity and Cleanliness High cleanness of a refrigerant and of all components used in the refrigeration circuit is always thermodynamically a big advantage. Some pollution can react under heat with metals, oil or oil additives and reduce the lifetime of a system. Materials used in food areas have to be known and controlled, if it does not contain any poison. Cleanliness Standards. Standards for the purity and cleanliness of R134a and of R600a refrigerants (in EU EN 378, in Germany DIN8960) and for cooling circuit components, such as tubes, condensers, evaporators, capillary tubes, heat exchangers, compressors and suction accumulators ( DIN8964 , an English translation is in Annex). Refrigerator companies normally use Isobutane 2.5 (=99.5% cleanliness), with in addition addition low limits on non-condensable gas, humidity, humidity, acids and other reacting substances, high boiling or solid substances, which could block capillary: Isobutane impurity limits

2)

Request of major refrigerator producers

Non condensable gas

-

O2, H2 N2 n-Butane n-C4H10 Propane C3H8 Unsaturated C 4 , especially -1,3 Butadiene CH2:CH-CH:CH2 Water content Acids

- CO, CO 2 High boiling fluids Solid particles Sulphur Chlorinated and fluoridated HCs Total impurities

1)

Purity %age by weight

2)

<100ppm

ajor suppliers of Isobutane 2.5 (99,5%)

1)

<2500 ppm <4000 ppm <100 ppm <1ppm < 10 ppm <1 ppm <20ppm < 0,01vol. % 0 ppm 0 ppm 0 ppm

<15 ppm <50ppm <2500 ppm <4000 ppm <100 ppm <1ppm < 12 ppm <1 ppm < 20 ppm < 0,01vol. % 0 ppm 1 ppm 0 ppm

<5000 ppm

<5000 ppm

Impurities of other gases and liquids by volume

The cleanliness and purity can be measured by Gas chromatographs with FID and TCD (HWD) Sensors (mainly HC’s and critical non condensable gases), humidity by capacitive Gold/Aluminiumoxid sensor or Karl-Fischer apparatus, Acid by test titration, boiling test, solid residue measurement (scale) and non-condensable gas test also by gas chromatographic or by Oxygen sensor acc. to US- ARI or German DIN standard. The mayor analytic problem is the splitting of signals of N-butane in ppm quantities inside of Isobutane with concentration above 99.5%, so only good laboratories in the world can measure correctly such small n-Butane quantities in Iso-Butane using Gas Chromatographs. Atom Emission Detectors in this area n- i- butane splitting are easier to use. Supplier for each batch of supply should approve it. See Transfair Engineering: Refrigerator Laboratory and Quality Control. Measurement of Cleanliness and Purity.

from the circuit can be removed during evacuation (see Transfair Engineering: Evacuation, charging, leak detection – 9/2003, p.9ff) and moisture from evaporator and condensers by dry air, but it is difficult remove it from the refrigerant itself and from the compressor oil in the refrigerator factories. These are the 2 severe quality problems as it is already in the refrigerant and in the oil. Refrigerant and oil humidity should not exceed 1/10 of dryer capacity (about 1g), that means for the compressor oil <100mg water (<125ppm for 280ml oil). The refrigerant value of <10ppm are often not reached by R600a suppliers.

Non-condensable gas

As hydrocarbons are mixable with all common types of oil except polyglycols there does not exist such problems like with R134a concerning humidity, solution of soldering etc. The selected viscosity grades are normally the same as for R12 or slightly higher, because Hydrocarbon is more soluble inside mineral oil than R12. It is a strong advantage for R600a that the compressor swept volume is 80% higher in comparison to R12, but it is a disadvantage that the pressure difference is lower, that the stress on moving parts is higher and that the housing of the compressor in same cases is bigger. bi gger. The mayor obstacle for the world-wide introduction of Isobutane as refrigerant, especially in developing countries could be perhaps the service problem. It is not only the problem of inflammability of hydrocarbons which will prevent the strong introduction in developing countries. Also the charging has to be made with a maximum tolerance of +/- 1 g because of the much lower charging quantities in comparison to R12. But meanwhile adequate equipment for a reasonable price is available. Charging without any adequate device as practised in the past in some developing countries from the informal sector cannot be made anymore.

Transfair Engineering: Engineering: Designing …Circuits. 7.3 Refrigerant, Working with R134a, Evacuation pumps and cleaning

p. 78

7.3. Working with R134a in the Refrigerator Laboratory and in the Production 7.3.1. R134a Refrigerant R134a (1,1,1,2-Tetrafluorethane) has a faintly ethereal odour, is colourless, chemically stable, free of acid, non explosive, non flammable, non- irritating and non-corrosive. Their toxicity is very low. Under normal temperatures it is a gas; the boiling point at 1.013 bar is -26,3 °C. At 25°C it can be kept liquid only under pressure of 6,5 bar. To avoid freeze burn any direct contact with the refrigerant like with R12 have to be avoided and the same measures have to be taken (gloves, Eye glasses etc.). General characteristics of R134a.

R134a can be mixed with Ester oil necessary for the compressor. Ester oil is hydroscopic; it is absolutely important to avoid any contact of R134a to mineral oil and humidity (above the very low limits fixed), because as a result of these contacts the ester oil will increase the acidity with drastical consequences for the life of the machine. In addition such contacts will cause residue in the circuit which will block the capillary tube and stop the circulation.

Ester oil.

Furthermore the Safety data sheet and first aid recommendations of the supplier should be respected.

7.3.2. Evacuation Pumps Vacuum pumps filled with normal mineral oil cannot be used for the evacuation of R134a systems. Only pumps which are filled with Polyol ester oil or with synthetic oil of low volatility, PFPE oil, can be used to evacuate such systems. In addition the evacuation time is normally prolonged to 20-25 min. to remove in the last stage any residuals, gasses or moisture from the system. Also the removal of gas ballast (20-30 min. each morning) out of the pump is more important as in the past when R12 was charged. Existing mineral oil filled pumps can be cleaned from fro m refined mineral oil and reused in the evacuation of R134a systems.

7.3.3. Cleaning Technology for Vacuum Pumps for R134a If vacuum pumps which have been used for evacuating of CFC 12 systems have to be used for HFC 134a refrigeration systems, it is possible to clean the pumps and use them, if:

(a) the vacuum pump is in good condition; (b) the pumps should have good final pressure press ure of about 0.005 mbar; and (c) the pumps should not have Viton gaskets, which are not compatible with ester oil needed for R134a, in case synthetic oil cannot be used.

In general the ester oil used for R 134a (or the special mineral oil with low volatility in case of pumps with anti-suck back valve) that will replace the mineral oil used for R12 should have the same viscosity as the one used for R12 according to Leybold (ISO Vg 100) while Galileo recommend to use for ester oil the viscosity of ISO Vg 68 instead of the mineral oil viscosity ISO Vg100. It is recommended to contact the producer of the pump to find out which oil he is recommending for its pumps. Polyol ester oil or PFPE oil.

We recommend using the same oil used for running the pump also for their cleaning,

Galileo recommend for all their pumps used for HFC-134a and for R600a charged cooling circuits the synthetic oil SH100 with low volatility: In the past past they recommend for R134a the ester oil Rotoil ES68 with viscosity of 68 (ISO Vg 68); Leybold recommend for their pump serial Trivac D8B or D16B following oils: Hüls: Anderol RFC96N, viscosity class ISO Vg 100 ( Supplier: Chemie Mineralien KG, KG, Bremen or Servo Delden BV, P.O.Box 1, NL-7490 AA Delden, Fax No. 0031-540775055); ICI Emkarate RL 68S, viscosity class ISO Vg 100 (Supplier: ICI Chemical Products, P.O.Box 90, Wilton,


Middlesbrough, Cleveland TS6 8JE; United Kingdom, Fax: 0044-642-432 444) or the synthetic mineral oil called with very vapour pressure from Hüls for both systems.

p. 79 PFPE

140

Cleaning process: 1. Replace the hose from the vacuum pump to the connector (Hansen coupling) for the service tube of the compressor (or filter) with a new one: 2. The connector (Hansen coupling) can still be used for HFC 134a refrigerator system; 3. Remove the oil out of the pump still warm from operation; Load the vacuum pump till tank minimum level (about 50-100cm² synthetic or ester oil) and start the vacuum pump. Let it run for minutes; 4. Repeat step 3 3 times with new synthetic or ester oil; 5. Remove the oil out of the pump, charge the pump with new synthetic or ester oil up to the maximum level; 6. Connect the vacuum pump to an HFC 134a refrigeration system and evacuate the system down to the specified vacuum level; 7. Connect the refrigeration system to the HFC 134a charging board and re-evacuate. Charge again with the specified amount of HFC 134a; 8. Start the compressor and let the system s ystem run for about one hour.

If some mineral oil or chlorine is still left in the vacuum pump on the suction side, it will be transferred to the HFC 134a refrigeration system and the capillary tube will be blocked after few minutes. If the vacuum pump has been washed with ester oil and not with the recommended synthetic oil with low volatility, it should only be used for HFC 134a refrigeration systems. If it is used for the evacuation of R12 or R600a systems it should have an anti-suck device or at least an efficient suction filter to avoid that mineral oil of the compressor can enter into the pump. The pumps, which are used, for R134a evacuation should be never used for re-evacuation of systems before filled with R12. or R600a and vice versa, if there is no anti-sucking device mounted.

Note:

7.3.4. R134a Charging Charging boards used for R134a must be free of mineral oil. Existing R12 charging boards can be cleaned from mineral oil, all sealing which can contain rest of mineral oil should be replaced. Production charging boards are working either with a mass flow meter or with a volumetric measurement. The parameters of R134a must be programmable inside such a system converted from R12 to R134a which is normally possible. Also the evacuation pump (see the last paragraph) and the refrigerant feeding pump must be cleaned and the sealing must be replaced before a charging board previously used for R12 can be used for R134a. There exists a huge quantity of new R134a charging boards for all applications.

7.3.5. Brazing R134a is more aggressive to brazing materials as R12. The selection of these materials and the way the joint are designed to avoid contact spaces are more relevant as in the past. Also the gas can pass smaller holes than R12, so that the system should be better sealed and controlled than in the past. How the brazing joints have to be designed and how to braze see Transfair: Cooling circuit sealing chapter 5).

7.3.6. Leak Detection The leak testing standard for R134a has to be improved because of the size reduction of the molecule and of higher reactivity with brazing materials as R12. At least a halogen leak detector which works with positive ion emission (thermo ionic method) and which is optimised for the detection of flour inside the halogen group should be used, like Leybold Inficon HLD4000A or Yokogawa Model H-25C. Newer model Inficon HLD5000 works with IR-sensor. Best would be for household refrigerators (and small other systems using capillary tubes the application of mass spectrometric systems like Inficon ECOTEC. The state of the art leak detection today is such a mass spectrometric spectro metric measurement in connection with a charge and recovery of Helium.


p. 80

7.3.7. Working with R134a Circuit Elements In general all R134a circuit elements have to follow the new standard of cleanness DIN 8964 to avoid blockages of the capillary tube. Following rules and instructions of work have to be followed during the working process of integration of the refrigeration circuit elements using R134a: 1. 2.

3.

4. 5. 6.

7. 8.

9.

can enter the refrigerant circuit elements (compressor, condenser, suction tube, evaporator, capillary tube, dryer, dryer, heat exchanger, exchanger, refrigerant). Specially solvents or chlorine substances (R12 (R12 etc.) should be avoided; Use in all equipment which will come in contact with the refrigerant (not only the circuit elements, but also the vacuum pumps and the charging boards and the equipment to produce the circuit elements) ester oil or oil compatible with it, but never mineral oil or greasy substances , in all cases in which mechanical work on the circuit elements are executed. Components made with mineral oil or grease must be completely cleaned from it. Don’t use any chlorine solvents for cleaning. It can be controlled by tests described in the standard DIN 8964 to be on the safe side. Take special care during the welding or brazing operations, but also during the processing of tubes, capillary tube, removing of zinc or aluminium coatings, burrs, to avoid the risk of entering solid residues in the circuit . The cutting of the tubes and the capillary tube must be made in a way, that - it should be as far as possible p ossible orthogonal, - the border of the inner hole has to be without burrs which easily can remove and enter in the circuit, and - the section of the hole should not be visibly deformed or oval. Do not use water containing desoxydants during the welding or brazing to avoid that humidity enters in the circuit. A nitrogen flow to avoid oxidation is sufficient. Avoid as far as possible an overheating of parts during the welding or brazing. The circuit elements have to be supplied according to the new cleanness standard, charged with dry Nitrogen and closed by plastic cabs to avoid entry of humidity, dust etc. The time which is needed between opening of the circuit elements (removing the plastic cabs) and their closing by welding or brazing should be as short as possible, under normal humidity conditions not more than 15 Minutes and under extreme high humidity conditions less than 8 minutes. The compressor which contains the hydroscopic ester oil should be opened in the last moment and welded or brazed first. For quality reasons it is even recommended to clean - before welding or brazing of the filter and the compressor - the other circuit elements by dry nitrogen or air (dew point < 40 °C) for 20 sec. Use only material in the circuit and during the operations of welding, evacuation and charging which are compatible with ester oil. The vacuum pumps and the charging boards have to be specially made for R134a (filled with ester oil and only to be used for R134a and not anymore used for a refrigerant containing chlorine (except some multi charging pumps and boards with filters on pump and separate charging hoses specially made for charging of d ifferent refrigerants). Use sufficient evacuation time of not less than 15 minutes, in regions with high humidity not less than 25 minutes with a pump of more than 8 m  /h capacity, drawn from one side and a vacuum level less than 0.5 torr. Recommended is an evacuation time of 25-30 min. By this way even water and other liquid residues will be removed. Avoid that any pollution

7.3.8.

Mixed Production during Transition from R12 to R134a or from R134a to R600a: Anti-Suck Valves, Suction Oil Separator or Glass Trap in Vacuum Pump

In cases such separation cannot be made in the production and the same evacuation and charging line have to be used for compressors charged with mineral oil and others charged with ester oil or both with synthetic oil of low volatility, special precautions has to be added to avoid charging of wrong refrigerant into the cooling system (R134a or R600a marking on the backside) and mixing of different oils from compressor and vacuum pump under normal operation and under power failure. In cause of power failure the already evacuated refrigerator cooling system will suck back oil from the pump is there is no anti-suck back valve built inside the vacuum pump. In such evacuation evacuation lines with HFC-134a systems mixed mixed with HC600a (or CFC12) either the pumps should be filled with ester oil or with the expensive mineral oil with low volatility (SH200). To Refrigerator To pump Oil Glas Trap for a mixed R600a-R134a Production

Anti-suck back valve

The repair of R134a and R600a on the same pumps is restricted by following conditions – in addition to the a.m. conditions for mixed evacuation lines: - a system already charged with R600a must be evacuated with a burst free evacuation pump, and not with a standard pump,


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- Refrigerators already running during evacuation as needed in case of R600a or during performance tests should be repaired on separate pumps, the R600a (or R12) ones on pumps with mineral oil and the R134a one on pumps pu mps filled with ester oil. The reason is that mineral and specially ester oil o il never completely separate from the refrigerant and will pass the cooling circuit and would enter into the hose and evacuation pump. But it is possible to use the same evacuation pumps – even for systems which have run already and which have oil in the condenser and evaporator the conditions, that an oil separator on the suction line must be installed on the pump, pu mp, the pump must have an anti-suck back device, and the used oil is a synthetic s ynthetic mineral oil with low volatility.

7.4. Working with R600a or R290 in the Refrigerator Laboratory and Production 7.4.1. Flammability and Hazardous Situations Isobutane and Propane safety data: Media

Isobutane Propane

Flash point [°C]

Ignition temp. [°C]

Explosion group

Temperature class

LEL/HEL vol. % Depending of country

Density (air=1)

- 83.15 -105

460 432

II A IIA

T2 T2

1,8 / 8.5 (35-165g in 1m³ air 2,1 / 9,5

2.05 1.56

For R290/R600a blends the the LFL is 1.95% blend in air and the upper flammability flammability limit (UFL) is 9.1 % blend in air. Concentrations between these limit values can be hazardous in presence of an ignition source like an open flame, an electrical spark from an electrical component or discharge of static electricity or a surface hotter than 460 °C.

Safety precautions.

Important is that an explosive mixture can build up even below the calculable concentration if the equipment carrying hazardous gas or the surroundings are made in a way that an accumulation in dead spaces, ground channels, pits or other deepening is possible.

A natural or artificial circulation (last one controlled by gas sensors and ventilator controls) of the air underneath the emission zones (R600a is heavier than air) should be insured and accumulations in the ground area or in a closed room should be avoided by using exhausts and ventilation. Clear instruction have to be granted to the operators and maintenance maintenance staff of the equipment which can come into contact with Hydrocarbon and their following needs to be regular trained and controlled. Hazardous situations. 1.

2. 3.

Following hazardous situations which needs partially different sa fety measures can happen:

Any open fire, an electrical spark of electrical equipment or discharge of static electrical loading, a surface temperature of 460 °C or above can ignite or even can let explode the hazardous hydrocarbon/air mixture. Fire from outside which reaches Hydrocarbon filled equipment or their leaks can let explode and burn down the equipment filled with hydrocarbon. Air leaks into equipment filled with Hydrocarbon. Normally all hydrocarbon filled equipment and tubes are under pressure and so such implosion can not happen except on the filling tube of the charging equipment. Production charging units therefore clean the tube with nitrogen to avoid any accident. In all other cases the 3rd hazardous situation can be neglected. Refrigerant leaks into the surrounding air.

7.4.2. Handling of Hydrocarbon Refrigerant Besides the a.m. safety precautions further handling precautions for these refrigerants are needed similar to the ones used for R12 refrigerants: Like R12 liquid Hydrocarbon on the skin will cause freeze burn and should be treated with cold water. Therefore gloves, goggles and protective clothing are needed to cover the body if refrigerant are handled in a way that liquid Handling precautions.

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quantities can escape. Hydrocarbon replaces air so by escaping of relevant quantities are asphyxiate and can cause suffocation. But R600a or R290/R600a blends are not toxic. As they are heavier than air they will distribute on the ground level and can concentrate to a hazardous mixture in pits, ground channels, channels, basements or any vessels underneath the leak. Therefore such areas need an additional ventilation to avoid explosion. Hydrocarbon cylinders. Such cylinders must be labelled being - inflammable with the ISO sign for it and marked with the - type of refrigerant the cylinder contains, like R600a, R290 R290 or R290/R600a 50/50 Blend.

-

In addition same rules as used for any high pressure gas cylinders have to be applied, like Closing the protection cap of the valve when cylinder is not in use, ensuring with a chain that the cylinder cannot fall down, do wn, avoiding the exposure of the high pressure cylinder to high temperature (>45 °C) and sun, if the cylinder must be heated to remove the gas, only a water bath or a PTC heater with a no -sparking limiter of temperature to max. 45 °C can be used, the cylinder or valve have neither to be modified or repaired, nor refilled again (for recovery special marked cylinders should be used), to check if a cylinder is empty a scale should be used and compared with the marked Tara weight on the cylinder. The pressure gauge mounted on the cylinder is not exact, avoid decanting of the cylinder in smaller bottles. Such work needs special equipment and precautions. Let it only do from your qualified refrigerant supplier.

The rules of transportation are the same as used for LPG. Such cylinders should be transported in open or good ventilated vehicles only from drivers experienced, well trained and authorised for the transportation of such hazardous goods.

Transportation.

Storage. The storage should be made like other light and inflammable inflam mable LPG gases. The best is to store the cylinders - outside in an naturally ventilated area above ground and never underneath the ground, upright, secured against falling down, and the valve and cap closed when not in use, - protected from weather and direct sun by a roof and - the area should be closed by an air passing fence and locked so that no unauthorised unauthorised person can enter and and manipulate manipulate

-

any valve. Minimum 5-10 m around the area no ignition source (electrical installation) should exist and smoking, open fire, electrical maintenance work work or welding in this area in presence presence of the cylinders have to be prohibited (ISO labels like symbol B 3.2 acc. to ISO 3864 or others according to local rules). There should be neither a window nor a door, nor any pit, basement or channel near the storage area to avoid that leaked gas can accumulate accumulate into a closed room or into lower areas (R600a and and R290 is heavier than air). Fire extinguishers have to be installed in this this area. The best would be if a water water extinguisher is place in a way that it can can be used even when there is a risk of explosion (behind a strong wall or corner. Staffs have to be trained in handling of the cylinders c ylinders and in case of accidents.

There exist also guidelines to store such cylinders inside a building; depending from the local rules. Such guidelines build classes of risks by quantities of flammables gas; they normally require a gas alarm systems, natural or artificial ventilation, fire protections and other precautions. But as these rules differ strongly from country to country and the storage outside is always much safer we prefer not to describe such storage s torage possibility to avoid generalisations. In all countries there exist rules and regulations how to use, to transport and to store such gases which belongs the group of LPG gas, and approvals for the installations and authorisations of their use are always required.

7.4.3. Evacuation Pumps The same evacuation pumps as used in the past for R12 filled with mineral oil can be used for the evacuation of R600a systems. A system already charged with R600a cannot be easily evacuated by a standard pump as there is a small chance that such a pump will explode. Leybold has developed a special ex-proof pump for this purpose. p urpose. The discharge of the pump must be lead to the open air by a pipe. Another solution is to use as pre-evacuation a venturi pump in the first stage to remove the hydrocarbon out of the system and compressor oil. Also in this case the pump discharge must guide into open air. It is needed to run the compressor during the first stage (10-15 Min.) to facilitate the removal out of the oil. Afterwards the system can be evacuated as usual with a standard pump.

Pay attention :

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7.4.4. R600a Charging In case R600a is used as refrigerant the existing service charging board can be used in the refrigerator laboratory as follows: follo ws: Service charging equipment.

A standard charging board as used in the past for R12 operated with an electrical pump which do not always fulfil the electrical safety requirement (IP54 for terminal boxes and switches and IP55 for motors) needed to use hydrocarbon (see chapter 8.3.) If electrical equipment is used underneath the IP 54 level special precautions have to be made to avoid that refrigerant can enter the electrical housing of the pump. A good ventilated area is needed and the distance between the gas cylinder and the refrigerator on one side and the pump motor on the other side should be 2 m and it is useful to position the electrical unit higher than the charging cylinder, the 3 way valve and the refrigerator. But pay attention:

The process of evacuation by an pump with a motor which do not follow the IP55 protection can be completely separated from the Hydrocarbon charging, for which only a exact electronic scale (like TIF 9050 deluxe or else) and a 4-way manifold (like Refco M4-3-BS-R600a)

are needed.

To avoid any risks it is better to use units already designed for Hydrocarbon charging stations like Refco 10854: Hydrocarbon charging boards.

If refrigerant is charged liquid into the suction part or into the compressor discharge line than it must be evaporated before it reaches the system to avoid compressor damage. This can be managed by using a short length of capillary tube between the hose and the system. This is not necessary if liquid refrigerant is charged into the liquid line or liquid receiver. Charging liquid into suction.

Safety approved production charging equipment. Their exist meanwhile from A’Gramkow (model Max 95F-1) and from Galileo (model Frigus H11) different production evacuation and charging boards with special feeding pumps (Galileo RP2 for HC, A’Gramkow R600a Supply System) specially designed for Hydrocarbon refrigerants and approved from different safety auditors, like German TÜV or Italian CESI following the required safety standards like IEC 60079-10, 15 and 16, CEI 64-2 and DIN VDE 165 and 105. Such charging boards contains internal controls on leaks of sealing, internal ventilation, Nitrogen flushing of the filling hose and a self closing quick reaction safety valve and overpressure relief valves for each section which can be closed by valves valves etc. between the Hydrocarbon tank cylinder and the machine.

The operation of such Hydrocarbon charging boards in the production area needs further safety devices normally put inside an alarm board, consisting of a gas sensor alarm system and a ventilator control (A´Gramkow Safe5+, Galileo Cerberus) and if the charged Hydrocarbon quantity per hour is not very small, like in the service of household refrigerators an exhaust and ventilation system is needed. Fire extinguishers have to be placed in the charging area and the staffs have to be trained in the use, the maintenance and in case of alarms and their skills have to be regularly controlled.

7.4.4. Exhaust and Ventilation of the Charging Area Artificial redundant ventilation can be used to increase the hazardous zone class from 0 to 1 200-500mm around equipment filled with hazardous gas and from fro m class 1 to 2 outside the direct emission zones. In such s uch a case the electrical safety requirements of electrical components around the emission zone are reduced. For example electrical components following IP54 standard are sufficient (see the standard IEC60079-16: Electrical apparatus for explosive atmospheres. Part 16: Artificial ventilation for the protection of Analyser(s) houses. and compare it to IEC60079-15 in Chapter 8.2. and the following chapters of 8. or with the CEI 64-2) The artificial ventilation has to be dimensioned in a way to keep in normal operation cases the concentration of

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hazardous gas underneath the lower lower explosion limit, for example on the level of 20% of the LEL. If artificial ventilation is safety relevant (depending from the released quantity, the existence of gas alarms and other local factors, than such a system have to be redundant, that means doubling of the ventilators, in case of any failure of a ventilator motor, and the ventilation has to be controlled (mechanical flow control inside the ventilation air stream or by measurement of the pressure differential. The formula for the ventilation is the following: The refrigerator charging area in the production need following ventilator output: Vc = a * 60 * Mair/M HC * 1/pair *100/LEL * 100/d % wherein:

Vc = Required ventilator output a = Average emission of HC (g/hour) = max. 120 * 15g = 1800 g Mair = Molecular weight weight of air = 28.97 g/Mol MHC = Molecular weight of R600a = 58,12 g/Mol pair = Average density of air = 1200 g/m³ LEL = Lower Explosion Limit = 1.8 % volume d % = % to which one wishes to delude HC underneath The LEL = 20% Vc = a *60 * 28.97/58.12 * 1/1200 * 100/1.8 * 100/20 = a * 6.9 m³/h

Important for this formula is the amount of Hydrocarbon which can be released. To reduce this amount their exist a lot of safety devices: Between the Hydrocarbon tank and the charging machine a self closing quick action safety valves are installed, so that the larger amount of Hydrocarbon Hydrocarbon in the tank has has not to be considered in case of leakage in the charging equipment. Also leakage on the sealing of the machine itself have to be and are normally controlled by the the machine itself which will cause cause a closing of the operation and closing of the quick action closing valves between the machine and the tank, so that emissions around the machine in such cases are strongly minimised under normal operation conditions. Therefore it remains for the calculation of the required ventilation output the average emission of HC during the normal operation of the charging unit. In case of the Galileo charging machine Frigus H11 for example a dead space of 1.8 cm³ will be purged by Nitrogen into the atmosphere and have to be considered and in case of a leak in the machine only 100g Hydrocarbon can escape. With a density of 0.555 g/cm³ at 20 °C and a cycle time of 30 sec. the emitted g Hydrocarbon per hour could be 120g which is about 2.4 m³ Hydrogen-air mixture on LEL level and the needed ventilation output should be minimum 24 m³/h to keep the concentration underneath 10% of LEL. In addition there exist under normal conditions rates of leakage on the manufactured refrigerators which will be minimised by a pressure rise test executed before charging can be executed. So only the small emission of remaining small leaks not identified by such a test has to be added. If we consider a 5% leak rate, an average charge of 50g and a cycle time of 30 sec. we have to add further 300g HC-emissions and further 60 m³ ventilation to keep the level underneath of 10% of the LEL value, totally 84 m³/h, with reserves 100 m³/h. Using such machines to charge household refrigerators with charges of 15- 40g for a small unit and 60-120g for large units a ventilation of the charging area is even not always needed, if an effective gas detector system is installed and if the machine controls their sealing and the safety quick reaction closing valve is closed automatically in case of leaks or alarms. But we still recommend the installation to avoid any accumulation and to increase the safety level. In case of an alarm and operation interruption the work can be restarted faster if a ventilation system is installed. It also has a positive effect on the detectable rate of leaks because the leak detectors near to the charging area are not disturbed. Standard electrical boards in the ex-zone area should be pressurised by air and the overpressure should be controlled by flow meters or differential pressure transducers to avoid entry of hazardous gas.

7.4.5. Alarm Board with Gas Detectors The concentration of inflammable gas in the Hydrocarbon charging area of a factory needs to be controlled by gas sensors. Such alarm systems have at least 2 alarm levels, often even 3: A first, so called pre-alarm (yellow light) for example when the hazardous gas concentration reaches 10% of the LEL value of 1.8 % gas volume in air, a second alarm (red light) on the 30% of the LEL, which will switch off the charging equipment. A third level alarm at 90 or 100% of the LEL will cause that all electric boards of the whole area will be switched switched off. The alarm board itself is built in a box following the IP54 standard. If a ventilation system is installed, the ventilator control should s hould be added to the alarm board.

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7.4.6. Fire Protection Rules and Fire F ire Extinguishers To protect the personnel and equipment against fire special rules to prevent any fire have to be established and their application regularly controlled. Special rules are not only needed in areas with potential leaks of Hydrocarbons, but also rules have to be established for the area around these zone to avoid any fire which can reach the risk zone. Any welding or brazing near the hazardous zone, for example the welding or brazing of the refrigerator circuit tubes, needs a permission of the engineer responsible for the safety and special arrangements have to be established, like a fire extinguisher on the spot, the presence of a supervisor able to use the fire extinguisher, to avoid fire and in case of fire to avoid their spreading out to the hazardous zone. Fire from outside which reaches Hydrocarbon filled equipment or their leaks can let explode and burn down the equipment filled with hydrocarbon. Powder fire extinguishers in areas with expensive equipment and water fire extinguishers for Hydrocarbon storage areas are therefore needed to protect this equipment against fire. If fire has already reached such equipment filled with larger quantities of hazardous gas, the personnel should escape from the area and only good trained and experienced staff can continue to extinguish the fire from far distance and behind a protection wall resistant against explosion pressure, till the fire brigade reaches the area. In case of a larger leakage (gas tube) the staff have to make sure that the hole building has to be put out of electricity to avoid any sparks and that all open fires have to be extinguished and heaters to be stopped and that all doors and windows have to be opened to increase venting.. The fire protection of the whole building should be sufficient according to the local rules (for example the standard EN 2 and EN 3 in Europe). In addition 2-3 powder fire extinguishers of min. 12 kg, better 50 kg on wheels should be placed around the charging area. The normally outside storage of the high pressure Hydrocarbon cylinders should be protected with water fire extinguishers fixed on a position, which allow the fire extinguishing even if the cylinders can explode. The fire protection measures need to be approved from the local authorities and the local fire brigades should be involved.

7.4.7. Grounding and Anti-Static Floor All metals of the hazardous area, the equipment in the charging area, the enclosure, the ventilation and exhaust tubes, the roller conveyer of this section and last not least the refrigerator cabinet which has to be charged must be grounded and the grounding should be measured (in the range of 0.5-1 Ohm, all parts in this area should have the same potential). The floor should be antistatic. Any sparking should be avoided.

7.4.8. Brazing How the brazing joints have to be designed d esigned and how to braze see Transfair: Cooling circuit sealing chapter 5 ). If the R600a charging tube is good closed by a crimping tool to be applied twice per tube, perhaps by a pneumatically driven one, it is possible to use normal welding to close even the filling tube. But today’s standard is to close the filling tube by e ultrasonic welding machines (like Viper from Stapla, RSA3000 from Stado or Ultraseal from Amtech) because of the flammability of R600a.

7.4.9. Leak detection We recommend to test every refrigerator not only by a leak test using leak detectors, but also by a pressure test with min. 8.5 bar (10 bar) dry Nitrogen for R600a respective min. 13 bars for R290/R600a blends. The pressurised system should withstand the pressure without any pressure falls several minutes (3-5 min.).

Pressure tests.

Hydrogen leak detectors working with 5% Hydrogen in 95% Nitrogen as well as HC-combustible leak detectors are not sensitive enough to reach leak rates underneath 0,5g/year –even not by the method itself – beside the fact, that often used Cyclopentane as blowing agent will case 50-100 times higher leak signals. Even molecule fraction specific mass spectrometric leak detectors as often used (for example Leybold ECOTEC II) cannot work reliable on a sensitivity level of leak detection underneath of 0.5g/year, because same mass fractions as detected for R600a are in the often Helium and Mass spectrometric leak tests.

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used Cyclopentane foam blowing agents already up to the level of 40-50g/year, so that such a system will cause often failure alarm. The only reliable method in this case is Helium leak detection lines. See Transfair Engineering text to Leak detection in the refrigerator industries today.

7.4.10. Further Precautions To avoid any ignition from the refrigerator unit itself the refrigerator should not be connected to the electricity and the design of the refrigerator should be made for Hydrocarbon (see ( see Chapter 8.). All electrics inside the charging area, all terminals, switches, light, other electrical equipment placed in this this areas, which can come in contact with the Isobutane in case of a leakage should be intrinsically safe or ex-proof acc. to IEC 79-15 standard with protection N or sealed acc. to IP54 or even better removed out of this area. Using R600a in the production, not only in the Laboratory, see Transfair Engineering: Evacuation, Charging, Detection and Performance Testing in the Household Industries Today T oday 2006; and the Transfair documentation supplied with the equipment.

7.5. Determination of Refrigerant Filling Quantity Before systematic tests of refrigerator cooling circuits can be executed including the optimisation of the capillary tube diameter and length on an existing refrigerator system we have to optimise first the charging quantity of the refrigerant to be able to execute further test. This test of determining the optimal refrigerant filling quantity has always been repeated if t he volume of the condenser suction tube, condenser or evaporator changes. Conversion from R12 to R134a. If an identical system will be converted from R12 to R134a the new refrigerant should have about the same volume. R134a has a 16% less mass volume than R12. So we we aspect a 16% less charge calculated calculated by weight. But in practice normally the condenser surface has to be increase so that the reduction of charge weight is lower lo wer than 16 %.

If we convert an identical system from R12 to R600a we aspect to charge R600a with a weight of about 40% of that of R12. We can receive a more accurate estimation if we take into consideration the different quantities of R600a respective R12 gases inside the used compressors. These figures we can receive from the manufacturer of the compressor. Hydrocarbon refrigerants are very soluble in the mineral oil so that a greater percentage will remain inside the compressor. On the other side we normally remove suction accumulators inside the system and we try to keep the R600a charge low to improve the performance. Conversion from R12 to R600a.

So series of tests are needed to optimise the charging quantity in each single case. The refrigerant filling quantity can be determined in the following way:

- In a test room the ambient a mbient temperature will be kept at 32 °C. - The evaporating temperature will be adjusted to -20 °C. At the starting point of the test series the filled in quantity of refrigerant should be slightly less than calculated according to the volumes of evaporator, condenser, suction tube and compressor and the mass volume of the refrigerant. Under these 3 conditions the quantity of refrigerant will be increased step by step of 2-3g in case of R134a and and of 0.5-1 g in case of R600a till the the measured temperature at the evaporator outlet shows an increase caused by b y superheat (compare Mollier i-log diagram in i n Chapter 7.1.79, temperature i). A slightly superheated system (+ 3…4°K) is useful. By reaching superheat measurable at the evaporator the optimal charge of refrigerant is reached. If evaporator with capillary tubes was correct selected the temperature difference between inlet and out should remain in the range of 1°K under running condition, not during pull down.

1 Inlet y r a l l i p a C

Evaporator Outlet 2

7.5.1. Refrigerant Charging: Liquid or Vapour? How a single system of refrigerators, air conditioners or other cooling systems should be charged depends on the experience, the geometry of the model and existing charging devices.

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In general a system can be charged either in liquid or vapour state. The upright refrigerant cylinder will allow saturated vapour charge, the upside down cylinder saturated liquid charge. Vapour charge is safer as it prevents that liquid is "slugging" the compressor. Liquid charging is much faster than vapour charging. If liquid refrigerant is charged into the suction line the compressor will be damages if the liquid is not evaporated before entering the compressor. The evacuation can be done in a way that the liquid charged refrigerant passes a capillary tube (1 m) before it reaches the suction. s uction.

Pay attention:

When you vapour charge a system that needs a complete charge, hook up the gauge manifold to the system in the normal way. The utility hose is connected to the refrigerant cylinder. With the system compressor off, and after you have bled the manifold hoses; open the refrigerant cylinder valve and the high and low pressure manifold valves. Control the refrigerant weight scale or charging cylinder. When it is obvious that the refrigerant is no longer entering the system or only entering very slowly, close the high pressure manifold valve and charge through the low pr essure valve only. When 50-75% of the total charge has been entered the system starts the compressor if Hydrocarbon is not used to complete the charging. The compressor will cool down or even freeze the refrigerant cylinder. If the procedure will slow down, warm the cylinder in a water bath up to 50 °C or with PTC heater with thermal fuses to avoid overheat. Liquid charging is always down in the high side of the system with the compressor off. Some larger refrigeration systems have a liquid charging valve between condenser and metering device. The system and the refrigerant cylinder are hooked up through a gauge manifold. After the manifold hoses are purged, the refrigerant cylinder valves are opened. Often the entire charge can be introduced by this way. When the whole charge does not go in, close the high pressure and refrigerant cylinder valves, turn the refrigerant cylinder upside down and introduce the remaining quantity in the vapour low side of the system with the compressor running.

7.5.2. Charging Accuracy Overcharging and undercharging will cause serious problems which should be avoided by using accurate charging methods . This problem will increase if Hydrocarbon as refrigerant is used. Undercharging causes flash gas to form upstream of the metering device. This starves the evaporator and will cause a low saturated suction temperature with excessive superheating of the suction gas with the effect of poor cooling of the hermetic compressor motor and thus endangers it. The discharge gas becomes overheated and the capacity and efficiency of the system are reduced. Overcharging causes fixed metering devices like capillary tubes or fixed orifices, to overfeed the evaporator so that liquid refrigerant floods back to the compressor. Liquid slugging will cause the compressor damage as well as a noisy operation, overheating inefficiency and wear. The high side pressure will increase in the condenser because of liquid backup in the condenser and will reduce the system capacity and efficiency.

7.5.3. Charging Methods Charging with Dial-A-Charge Cylinders .

This accurate method of charging is used for servicing household application (limited charging quantity) and adjustments of charges in larger applications as the level of refrigerant to be viewed in the charging cylinder and its graduation scales permits to charge the correct amount (see operation manual of charging stations supplied) as long as the refrigerant is liquid under environmental temperatures. For larger applications the charging by weight method is the best. But even for small quantities and for Hydrocarbon refrigerants which are gases under normal temperature and pressure there exists nowadays very exact scales with very high accuracy to allow the accurate charging of small refrigerant quantities as used for household refrigerators. The accuracy should be within within 0,5% of the total system charge if non Hydrocarbon refrigerants are used. Hydrocarbon charged Charging by weight.

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household refrigerators need an accuracy of +/-0.5 g. Register the starting weight and calculate the final desired weight before starting of charging. Some scales are even made to program the needed charge. The charging is completed when the final weight is archived. Do not move the gauge manifold and hoses during charging to avoid false weight indications. Systems with sight glasses in the liquid line close to the inlet of the entering device allow identifying the correct charges. A system with bubbles (mixture of liquid and gas) are undercharged. Only pure liquid should enter the metering device. But a clear slight glass can also indicate a severe undercharge if it is pure gas or an overcharge (liquid). Therefore this charging method allows only the charge starting from undercharging (clear sight glass caused by PURE gas or already bubbles caused by mixtures of gas and liquid refrigerant) till the sight glass- after passing the bubble stage - become clear. When this will happen saturated liquid is obtained. Some manufacturers require an extra charge above the saturated level to establish the desired sub cooling leaving the condenser; other manufacturers may instead indicate a desired liquid line temperature to be reached by adding smaller quantities during operation of the system. More charging increases the sub cooling and lowers the liquid line temperature. So pay attention in this method: clear sight glasses can be pure liquid (correct or overcharged) or purr gas (strongly undercharged). Charging by sight glasses.

7.5.4. Fine Tuning and Control of Charge Fine tuning and control of charge with charging calculation charts and already executed performance test can be made with the so called superheat and/or with the sub cooling method. Such methods are sometimes used also in the service sector of large appliances. In this case the manufacturer of the appliance has provided data for checking a system while it is in operation: like charging charts, charging calculations and performance charts. They can be used to check a factory - charged system and to adjust the charging by measuring the inside and outside temperature as well as the refrigerant pressures and comparing these measured data with the charts or calculated data. One method to adjust the charging of a system already in operation and tested by performance test is to measure the refrigerant superheat in the vapour line. This approach can only be used for systems with fixed metering devices like a capillary tube in the household hous ehold refrigeration but not with throttle devices. Charging for proper superheat (Superheat method).

Superheat is the temperature added to the refrigerant vapour at the end of evaporation/compressor suction above its saturation temperature (typically for the household refrigerators: 2-5 °C and for air conditioners: 5-8 °C). Often as much superheat as possible should be obtained between evaporator outlet and compressor inlet. Probably performed the superheat method is a very accurate way of checking and adjusting the refrigerator charge: Only 1% changes of a system charge will cause a change of superheat by 1,7 °C or more, if R134a is used. In case of R600a the increase can be even higher. Measurement.

-

-

The system should run as "cooling-only" (bridging (br idging of the thermostat cut off). Install one thermocouple on the suction line and insulated the probe well. Install the pressure transducer in the suction line. Run the system for 30 Minutes to allow system temperature and pressure stabilisation. Take inside refrigerator and freezer temperatures and environmental temperatures and read the pressure and the temperature of the suction line. Use the refrigerant pressure/temperature calculation program or table to determine the saturation temperature that that matches the pressure for the suction line. Subtract the saturation temperature from the actual actual suction line temperature, compare it with the requested superheat of 35°C for household refrigerators respective 3-8 °C for air conditioners. conditioners. By increasing the charge charge the superheat will will drop, by reducing the the charge the superheat will increase. If the superheat is 2-3 °C above the superheat value recommended recommended for the system by the refrigerator design company and/or compressor compressor manufacturer add liquid refrigerant to the compressor compressor inlet (compressor not running) or vapour refrigerant through the low side service port with compressor running.

It is too low by more than 2-3°C, remove vapour refrigerant. After any charge adjustment repeat the measurements of temperatures and pressure to control if the system is adjusted to the required superheat.


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The charge of systems using devices with thermostatic expansion valves (larger air conditioners and refrigeration machines) cannot be controlled by the superheat method as such devices maintain a constant superheat over a wide range of load and charge conditions. In such cases the measurement can be made in the liquid line using the sub cooling method. Charging for proper sub cooling (Sub cooling method).

Sub cooling is the temperature removal from fro m a refrigerant liquid below its saturation temperature. A typical s ub cooling value for a refrigerant entering the metering device (expansion valve) o f an air cooler air conditioners' system is in the range of 3-8 3 -8 °C. The charts of the air conditioner manufacturer for the specific conditions and loads should be used for fixing the value of sub cooling which refrigerant charge should reached. Run the system for 20-30 Minutes to stabilise the pressure/temperature values with cooling-only (No thermostatic cuttings). Measurement.

- Register the temperature and pressure in the liquid line. If the system has a liquid charging valve, attach the high pressure hose to it and make your pressure readings there. If you have only a high side system access port near the compressor discharge, take the pressure readings there and subtract 0,07 bar (10psig) to allow for condenser pressure drop. -Use the refrigerant pressure/temperature calculation program or table to determine the saturation temperature that matches the pressure just found by the pressure transducer. Subtract the actual liquid line temperature from the saturation temperature. This figure is the system's sub cooling value. More charge will increase the sub cooling; less charge will reduce the sub cooling. If the sub cooling is too low by more than 1,7°C, add vapour refrigerant through the low-side service port with the compressor running. If it is too high about more than 1,7°C above the value recommended by the manufacturer, remove vapour refrigerant through the high-side access port (use recovery units). After any adjustments of charges repeat the measurement procedures to be sure that the charge is within the correct corr ect range.


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Transfair Engineering: Engineering: Designing Designing …Cooling …Cooling Circuits. 8. Safety requirements, Special Safety Safety Requirement Requirement for for HC-Refriger HC-Refrigerators, ators, Electric Electric Safety Tests

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8. Safety Requirements of Refrigerators – especially with Hydrocarbon Refrigerant 8.1. Safety Standards for Refrigerators and Freezers The safety standards specify which electrical safety rules the manufacturer have to respect, which electrical components acc. to which electrical standard he can use in the appliances and which kind of tests he needs to make on prototypes for the declaration of conformity (CE, etc.) and to which production quality control tests must refer. Following international valid safety standards exist for refrigerators and freezers: -

IEC /EN/UL/J/GOST etc. Standard 60335, Part 1: Safety of household and similar electric appliances, and IEC /EN/UL/J/GOST etc. Standard 60335, Part 2-24(2005-04): Particular requirements for refrigerator appliances and ice makers. (This version 6.1. contain version 6 (2002) and Amendment 1 (2005). Meanwhile there is

another amendment 2 (2007) as result of changes in referred standards (ISO15502, ISO3864 and IEC60079-15). The electric safety of commercial refrigerators is described in IEC 60335 part 2-89 and of commercial dispensing appliances and vending systems in IEC 60335 part 2-75; the ones of motor-compressors in IEC 60335 part 2-34 . Such standards have to be applied in addition to the performance standards of refrigerators as described in the next chapter and in addition to the electrical standards IEC/EN for each used electrical part and in Europe the EU Low Voltage Directive (73/23/EEC) as amended 93/68/EEC.

8.2. Special safety requirements for refrigerators using a Hydrocarbon refrigerant After the introduction of Hydrocarbon as refrigerant the a.m. standard for the safety of household refrigerators and freezers was amended. R600a (C4H10) and R290 (C3H8) are flammable refrigerants and have been classified A3 in accordance with ANSI/ ASHRAE 34. Consequently certain safety instructions should be observed. New safety standards for refrigerators filled with Hydrocarbon refrigerant like R600a, R290 or R290/R600a blends are already introduced. In 1995 the CENELEC committee recommended to amend the existing IEC 335-2-24 (3rd edition) to cover potential risks originated from the use of flammable refrigerants and to integrate a special CENELEC Test Schedule TS95006 for such refrigerators into the standard. With the 2002 amendment it meanwhile became a worldwide valid standard: Safety of household and similar electrical appliances. Part 2: Particular requirements for refrigerators and food freezers. Use of flammable refrigerants. IEC/EN/UL/J/GOST 60335-2-24(2005):

In 2004 this standard was again amended (Amendment 1) by EU CEN/CENELEC and IEC now version 6.1 to carry out risk assessment and test procedures for inflammable refrigerants, like R600a, by integrating risk assessment rules CEN/TR 14739 (2004) and test procedures TS95006. It based on the application of the existing electrical safety standard for equipment exposed to explosive atmospheres IEC/EN 60079-15 Electrical apparatus for explosive gas atmosphere. Part 15: Electrical apparatus with type of Protection “N” and explosion limits applicable for R600a and R290.


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So refrigerators with inflammable R600a and R290 refrigerants need some special designs and precautions and type tests which can differ from the previous considerations of designing and specifications. In this chapter these special design problems and their solutions will be described. A small modification of IEC60335-2-24 become valid with amendment 2 on 20 07-01 (compressor sound; warm damp equable climates). Its actual version in 2010 is Edition 7. IEC60335-2-89 was slightly amended in 2005 and in 2007. Its actual version in 2010 is Edition 2

8.2.1. Flammability and Hazardous Situations Isobutane and Propane safety data: Media

Flash point [°C]

Ignition temp. [°C]

Explosion group

Temperature 1) class

LEL/HEL vol. % Depending of country

Density (air=1)

Isobutane - 83.15 494 IIA T2 1,8 / 8.5 (43-165g in 1m³ air) 2.05 Propane -105 470 IIA T2 2,1 / 9,5 (38g in 1m³ air) 1.56 For R290/R600a blends the LFL is 1.95% 1.95 % blend in air and the upper flammability limit (UFL) is 9.1 % blend in air. 1)

The IEC60335-2-24 (2005) Para 22.110 respective 89 (2002) Para 22.109 allow maximum surface temperature to be exposed to leakage of flammable refrigerator 100K underneath above mentioned ignition temperature >350°C; that is why we specify T2<300°C and not only T1<450°C.

Concentrations between these low and high explosion limit values can be hazardous in presence of an ignition source like an open flame, an electrical spark from an electrical component or discharge of static electricity or a surface hotter than 470 °C respective 494°C. Important is that an explosive mixture can build up even below the calculable concentration if the refrigerator construction is made in a way that an accumulation in dead spaces or deepening is possible. A natural circulation underneath the refrigerator cooling circuit should be insured by using the temperature differences during running. Also some user instructions were to place the refrigerator in the household and labelling o f the refrigerator is needed. On the refrigerator appliance we can identify 2 potential hazardous situations which need partially different safety measures: 1. Refrigerant leaks into the surrounding air, 2. Refrigerant leaks into the food compartment, normally closed, so that a concentration above the lower flammability limit can easily be reached.

Last can only happen if the evaporator is - inside the food compartment or if the evaporator is - foamed-in behind the food liner, has joints in the evaporator pipe work and if the inner compartment is not completely sealed, for example if there are holes for the thermostat capillary tube and for the power supply cable of the light-switch combination. The 2nd situation can be avoided, if the construction is made in a way that no leaks can go into the food compartment. Normally defrost models today are made in this way in Europe. But the sealing must be tested (see ( see underneath). . The 3rd hazardous situation, air leaks into the system (as the suction pressure is underneath the atmospheric pressure) can be neglected. It would be very rare that there exist sufficient air inside the system for combustion. Even if combustion inside the system could happen, according to tests executed by Liebherr and others the maximum pressure peak of 12 bars created during explosion in the cooling circuit remains under the critical load loa d of any cooling circuit components. Also the 4th hazardous situation that fire from outside will burn down a hydrocarbon filled refrigerator can be neglected. In comparison to conventional R12 or R134a refrigerators the risk to be injured is even lower. In 1997, fire tests executed by Calor Gas in Britain on commercial ice cream freezers showed that there was no significant difference in the fire intensity and fire duration of refrigerators filled with hydrocarbon in comparison to R12 filled systems. High fire intensity was required for failure of the pressure system. The compressor withstood the fire. Failure occurred through brazing joints. More important than the fire it was the observation on the fumes. People in case of fire are seldom killed by the fire itself but by toxic fumes, which in case of R12 is an important risk increase not existing with hydrocarbons. (See Calor Gas: Fire Test Report Application of CARE Refrigerants. Warwick 1997).


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8.2.2. Sealing of the System Such systems require much more care on the sealing of the system as in R12 or R134a systems. In the design of the cooling system is already important, where joint are placed, how they and specially the capillary tube are protected against mechanical damages during packing and de-packing, transportation or use through cleaning or de-icing. Important is how each tube joint itself is made to avoid mechanical damage. Even some joints can be and should be avoided, for example between 2 evaporators or some prolongation tubes in the compressor compartment. Also how the necessary tube joints are made inside the manufacturing is important, the experience and quality efforts and control of workers doing the brazing, the ultrasonic welding or the mechanical closing with lock rings or else. The brazing alloys, their positioning, quantities or shape and the used flux are very important (see Transfair Engineering: Evacuation, charging, leak detection and performance testing chapter 5. Sealing). Nevertheless each joint must be more carefully and with much more sensitive and selective methods the past. Mass spectrometric leak tests, or even helium leak tests are recommended.

tested on any leakage

as in

Even with highest efforts in this field of sealing ignition sources must be avoided in areas where hydrocarbon leaks can occur. Evaporator behind foodliner (3) .

Standard defrost models often install evaporator behind the foodliner and keep standard sparking thermostat, light switches and hot light inside compartment. The foodliner prevents that flammable refrigerant can come into touch with this standard electric components (see underneath chapter 8.2.4.); leak tight closing of holes for the thermostat capillary tube and for the power supply cable is here essential; but tightness has to be type tested by a leak simulation test according to IEC60335-2-24 clause 22.107.1 or IEC60335-2- 89 clause 22.106.1. Electric component in top (2). Others relocate such electric parts with ignition outside cooling compartment, for example in refrigerator top . In a type test it has to be

sources (electric sparks, hot surface) checked that no flammable refrigerant can touch such electric item according to IEC60335-2-24 clause 22.109 (2005) or IEC60335-2-89 (2002) clause 22.108.

Meanwhile very seldom is the use of double layers components, like double layer roll bond, double wall wall No Frost coil evaporators, because of their their high prices. IEC-600335-2-24, clause 22.107.2 or IEC600335-2-89, clause 22.106.2 require a scratching tool test that double layer are mechanically strong enough. More in use are following modified electrics: Double layer refrigerant carrying components.

If separation is difficult, electrics can be sealed or by other means mentioned in IEC60079-15 to prevent sparks and hot surfaces (IEC60335-2-24 (I EC60335-2-24 clause 22.108 and Annex CC or IEC60335-2-89 clause 22.107). “N” protected electrics (1).

Let’s take a closer look to the potential ignition, the mentioned strategies to avoid explosion and required t ype tests:

8.2.3. Potential Ignition Sources Refrigerators can have following ignition sources: Loose electrical connections (terminals, plugs and sockets on compressor electrical box, power cable, terminal blocks, light, switches, thermostats, etc.) unsealed compressor overload protection (Klixon), unsealed compressor relay, start and run capacitor with unprotected leads, on/off switch, door switch, Thermostat, In case of NO frost models in addition: defrost heater and defrost control (timer, defrost thermostat) Fan motor and blade. On appliances where leaks can enter the food compartment additional ignition sources must be considered: Thermostat, Light and light switch, In case of No Frost: Defrost thermostat and temperature control


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Fan motor and blade. A risk assessment and approval tests have to be carried out according to actual version of standard.

8.2.4. Separation of Ignition Sources from Potential Leaks One often used and for many models the least expensive way of minimising any risk is to modify the construction in a way that electric sparking components are placed in areas where no explosive mixture can be built up in case of any leakage. In standard defrost model the evaporator can be mounted outside the food liner and foamed in so that no leak can enter inside the food compartment and no special protection or precautions are needed for the electrical components inside the food compartment. Important for such a construction is that the food liner is closed. Holes to allow the passing of the cable and/or the capillary tube of the thermostat should be avoided or specifically sealed and controlled. Also joints in the foamed in evaporator should be as far as possible avoided and not near to sealed holes. Such models have to be type tested by a leak simulation test according to IEC60335-2-24 I EC60335-2-24 or 89 clause 22.107.1. See chapter 8.5.3. underneath. Standard defrost models.

Concerning the R600a or R290 compressor and the needed tube joints in the compressor compartment , there is no chance of such a separation so that all electrics in this area must be protected or spark free (see next chapter), which is meanwhile standard for all compressor manufacturers according to actual version of IEC60335-2-34 for compressors. Another solution exist for one door models or freezer compartment with standard defrost if the evaporator is left inside inside the food and/or freezer compartment without using expensive double layer evaporators (the disadvantages of roll bond evaporators often used in such cases cases are described in chapter 5.2.5.). In such a case all electrics (thermostat, light, light switch and terminals can be removed from inside the food compartment and built in the upper front plate. Freezer compartment in 2 door models seldom have any electrics. R600a, R290 and their blends are heavier than air. In case of any leakage on the backside of refrigerator or freezer the small quantity of R600a will be rarefied in ground direction. In case of a leak inside the compartment, there exist no electrics anymore inside. By opening the door the heavier gas and heavier cold air will move to the ground area and rarefied so that no explosive mixture can be built up on the level of the upper front plate. Such models have to be type tested by a leak simulation test according to IEC60335-2-24(2005) clause 22.109 or 89 clause 22.108 (2002). See chapter 8.5.5. underneath. One door models or freezer compartment with inside evaporator.

In some models relocation of thermostat or switch are more expensive as its enclosure and sealing according to “n” protection. All No frost models do not allow all ow such a separation and need special selected electrical components which have to follow the I EC standard 600079-15 or must be replaced by components without electrical sparks like solid state switches (PTCs) or the sparking components must be completely sealed. Such spark free components must be chosen for all electrical components in the compressor area and even in the food compartment when the a.m. separation cannot be made or where it is cheaper to use such spark free components (see next chapter) instead of the separation of flammables from electrics. But such ‘n’ protected parts have to be tested by the component manufacturer. He has to declare the conformity of his model parts with the standard IEC60079-15 or to present a conformity declaration of an authorized body according to IEC60335-2-24 clause 22.108 and Annex CC for household refrigerators refrigerators and IEC60335-2-89 clause 22.107 for commercial refrigerators, before they can be used in the refrigerator. Further details of such components see next chapter:

8.3. “n” Protected Electrical Components in Hydrocarbon Leak Areas The requirements of electrical components installed in areas with potential leaks of hydrocarbon like R600a or R290/R600a blends should follow strictly the new amendment of the IEC 60335-2-24 clause 22.108 and Annex CC or IEC 60335-2-89 (2002) clause 22.107, which both following now the IEC 600079-15 standard about electrical apparatus for explosive gas atmospheres type protection ‘n’ to be applied to on refrigerators and freezers using flammable refrigerant. It includes the requested test methods, requests of Manufacturer’s Declaration of Conformity and approvals of new models and components. co mponents. Important : Refrigerator manufacturers should not use any electric components ins ide areas with potential leaks of flammable refrigerant without such manufacturer’s type tests and its declaration of conformities or approvals of 3 party authorized bodies according to IEC 600079-15.

rd


8.3.1.

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Electric Connections

Electrical connection are considered as not normally sparking if they are made in a way that they cannot be disconnect by use, vibration or accidentally. Brazed or welded wire connections are acceptable. Also wires with crimped terminals screwed to a contact. Plugs and sockets are acceptable if the separation force exceeds 15N and if they meet in their construction the standard IEC600079-15, especially chapter 14. The quantity of electrical terminals in the hazardous area should be limited.

8.3.2.

Compressor Relay

The best is to use a sealed or solid state (PTC) relay which cannot give any spark. Other solutions with a sparking relay in a sealed box need an approval acc. to the valid standard like IEC 600079-15 and EN 60730-34. PTCs are better than sealed boxes because seals can be damaged by incorrect repairs.

8.3.3.

Compressor Overload Protector

Standard external overload protectors (like Klixons) cannot be used except in sealed and approved boxes. Solid state or sealed protectors without any sparking can be used. Also special combined compressor relays and overload protectors made, sealed and approved acc. to the IEC 600079-15 can be used. Today’ R600a and R290 compressor models have to comply with IEC603352-34 and are not critical anymore.

8.3.4.

Compressor Start and Run Capacitors

Even if the capacitors themselves cannot produce sparks the leads connected to them can! So called integral leads (flying leads) can fulfil the requirements of IEC 600079-15 and have to be used to fulfil IEC60335-2-34. International compressor manufacturers are supplying the HC compressors with approved electrical devices like terminals, relays, overload protectors and, if part of compressor, capacitors (chapter 8.5.1-4) acc. to the new standard IEC 60335-2-34, which integrated the Hydrocarbon safety requirements so that the refrigerator manufacturer does not need to make own constructions, tests and approvals on this components according to chapter 8.3.2.-8.3.4 and IEC60079-15.

8.3.5.

On-Off Switches and Light Switches

On-off switches of refrigerators are often not needed and can be easy eliminated. In single cases if they are still needed, they should be placed as far as possible away from the refrigeration circuit in the upper area of the refrigerator to avoid the risk being in flammable atmosphere. After the relocation it has to be tested that no explosive gas can reach it (chapter 8.5.3.; IEC60335-224 clause 22.109 or IEC60335-2-89 clause 22.108). If this separation from hazardous areas is not possible standard sparking switches cannot be used and must be replaced by non-sparking sealed versions as used out doors in a waterproof version and approved acc. to IEC 600079-15. The same has to be applied for the door light switch: If it is not placed inside the food compartment or outside the door in an area leaks can reach according to executed type tests only sealed door switches can be used (see Chapter 8.4.).

8.3.6.

Luminaries, Lamp Holders and Fluorescent Lighting Ballast and Starter

First condition is that the temperature of the lamp is not exceeding 350°C. Filament, tubular fluorescent or other discharge lamps can fulfil this condition. The lamp rating concerning temperature class T2 must be printed on the lamp and confirmed by the manufacturer. Even lamp holders, which are non-sparking in normal operations, shall be made in a way that arc, sparks or hot spots are minimised. Their construction have to follow IEC600079-15 Paragraph 21 and requires enclosure and special fixing, torque


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strength of screw lamp holders and other specifications, like non-sparking plugs and sockets Para 20: A E14 respective B15 lamp to be fixed with 0,15Nm or a E27 respective B22 lamp to be fixed with 0,25Nm into its lamp holders shall withstand a push force and a pull force of 10N+/-1N for 1 min in direction of the axis of the lamp holder. A lamp holder used in a hazardous area, the way of its fixing and terminal connection should follow this standard. Often screw lamp holders with a rubber lid for water proof are fulfilling the requirements of this standard. Fluorescent lighting ballast and starter are normally made not to be ignition sources. Starters are tested by lamp manufacturers according to IEC60079-15 Para. 33.10 and declared to be confirm: Normally only sparks can happen on loose contacts, terminals plug and sockets so that the considerations of chapter 8.3.1 has to be applied.

8.3.7. Thermostat Standard thermostats have bodies with open contacts which can spark and cannot be used in hazardous areas. Either the thermostat is relocated outside the ex-zone and their position is type tested according to the standard, that leaked refrigerant can not stagnate in areas with such a sparking component or only sealed or solid state thermostats can be used which follow the requirements of IEC 600079-15. Even a standard thermostat can be used if it is inserted in a sealed box following the IEC 600079-15 standard, but good thermostat manufacturers (Invensys, Danfoss etc.) have such sealed models with certificates from authorized bodies in the supply program with nearly same price p rice as their standard thermostat version.

8.3.8. Fan Motor and Blades The major fan motors to ventilate air on fin coil evaporators (No Frost models) or on fin coil condensers uses today sealed induction motors (squirrel cage shade pole motors) following already the IEC 600079-15 with “n” protection, so that they do not need to be replaced in case hydrocarbon refrigerant is used. DC-motors with commutator and brushes are forbidden, but anyhow rarely used in such an application. Also the fan blade should be made of a material that there is no sparking possible (not ir on). Furthermore the fan motor should not reach excessive temperature (<350°C for R600a) if the motor locks or could not start (locked-rotor test to be executed according to IEC 60335-2-24 60 335-2-24 Annex AA).

8.3.9. Defrost Heater and Thermal Fuse (in No Frost Models) Asian and American No Frost models are normally using infrared defrosting heaters, European resistance heater. The rule is that the surface temperature should be 100 °K underneath the ignition temperature. Infrared heaters often above 350 °C are forbidden. Resistance heater limiting the electric heating power per surface to 1,5W/cm² with special limiters to limit the temperature to max. 350 °C can be used.

8.3.10. Defrost Probe, Temperature Cut-Out and Defrost Timer Control (in No Frost Models) The existing defrosting probe, temperature and defrost timer controls as used on No Frost models can spark under normal operation conditions. Parts which are placed in areas with potential leaks must be replaced by ones which meet the IEC 60007915 requirements. Bimetal temperature probes can be quite easily sealed. But there exist often the possibility to relocate parts like timers in areas where no explosive mixture can be built up (for example in the table top) which should be checked first and tested according to the mentioned IEC 60335-2-24 standard clause 22.108 (our chapter 8.5.3.) to avoid often more expensive electrical components following the IEC 600079-15 standard.

8.3.11. Sealed Box IP54 or higher Instead of replacing sparking electrical components by non-sparking or sealed ones it could be in some cases cheaper to enclose such components in a sealed box which follow at least the IP54 rating for sealed components. IP54 components are dust and splash proof and are considered by European specifiers sufficiently sealed to reduce significantly the probability of combustion in the event of a leak, but only if the gas cannot accumulate in this area . Important is that the sealing gasket is permanently


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fixed and that it cannot be removed during service or that it cannot be wrongly positioned. It is absolutely necessary to mark the lid of such sealing boxes with a label showing the importance of replacing the lid to maintain maintain the sealing. The cable entries should be made via terminals permanently fixed to the box and through glands. Any possibility to use other, not sealed entries as the protected ones should be avoided by the construction of the box. This sample of sealed box and service precautions shows the problem which we can face in areas with informal refrigerator services. Any solution which separate the leak risk areas from the electrics by relocations and which can use standard electrical components are preferable to solutions which depend on qualified service which will not destroy the sealing.

8.3.12. Manufacturer’s test of electric component for flammable gas atmosphere, conformity declarations and markings The manufacturer of all electric components used in potential leak zones of flammable refrigerant must execute type tests according to IEC60079-15 mainly para.33, grant the conformity declaration for it and mark its product including temperature class T2 or higher to allow refrigerator manufacturers to use them in such hazard zones. Components not tested and approved according to IEC60079-15 or other IEC60079 clauses are not allowed to be used in these potential leak areas.

8.4. Labelling of Hydrocarbon-Refrigerator Appliances charged with Hydrocarbons must have a label stating in local languages of the market as well as in common foreign language that the refrigerant is flammable. It also should explain how such a system has to be repaired. The label should have following information: - refrigerant type and/or composition like R600a, R290 or R290/R600a blend in 50/50% by weight or else and the amount of charge needed; - the refrigerant is inflammable (previously ISO 3864 symbol B 3.2); - if the refrigerant has to be vented or the refrigerator to be charged with Hydrocarbon refrigerant, the refrigerator has to be positioned outside a building or in an well ventilated area, no flames, cigarettes, unsealed electric equipment or other equipment which can spark or with surfaces above a temperature of 350 °C should be within 2 m around the refrigerator positioned in a

ventilated area.

8.5. Electrical Safety Tests and Controls 8.5.1. Electrical Safety Tests for all Household Appliances There exist special standards like the IEC60335-1 and 2-24 or 2-89 which regulate the electrical safety requirements of refrigerators and freezers, their control and testing for type conformity approval (CE etc.). Beside of the specific ones concerning hydrocarbon refrigerant there are several tests and controls to be executed (see these standards) like in past with no flammable refrigerants, not here described, like Protewction against access to live parts (para 8), heating (para 10), resistance against moisture (para 15), heat and fire (para 30), rusting (para. 31) etc. all needed for type testing. Furthermore the manufacturer has to insure that each produced refrigerator and freezer follow the requirement fixed for the type approval, by quality controls (leak test, pressure test, electric tests and inspection of correct mounting etc.). Often following electrical safety tests are applied on all produced refrigerators and freezers (class 1 with PE): •

Earth test with <12Vac/25A and threshold R-PE<0,1  in 2-5s;


• • • •

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High voltage (Dielectric strength) test at ≥1000V (often at 1250V) for basic insulation or ≥3750V for reinforced insulation with threshold <3,5mA; Leakage current test with 1.06x rated voltage I-PE <3,5mA and/or Insulation test with 500Vdc and threshold between L-N and PE>1M  (basic insulation) or >7M  (reinforced insulation) Absorbed current and power test with threshold value to be fixed per model to assure energy labelling class values; Residual voltage test (only needed for on models with capacitor) with rated voltage and threshold value <60V to avoid electrical shock on de-plugging.

In addition other parameters like correct wiring, earth connection, IP54 sealing, functioning of all electrical components like switches, thermostats, signal lights, light switches, light should be inspected and/or tested. The safety standards specify which electrical safety rules the manufacturer have to respect, which electrical components acc. to which electrical standard he can use in the appliances and which kind of approval he needs.

8.5.2. Pressure Test of Refrigerators Charged with Hydrocarbon The IEC/EN 600335-2-24 section 22.7 requires a pressure test on circuit components at least as type approval . They should withstand an absolute pressure of 3.5 times of the saturated vapour pressure of the refrigerant at 70 °C for parts exposed to the high side pressure during normal operation, that means 35bar rel.; 5 times of the saturated vapour pressure of the refrigerant at 20°C for parts exposed to the low side pressure during normal operation, that means 10bar relative; The pressures are gauged pressures. Also the EU PED Directive requires such tests. R600a and R290 in household and commercial refrigerators are category 1 (<50p*V at saturated low and high pressure), s o pressure test have not be repeated during refrigerator lifetime. This IEC/EN 600335-2-24 section 22.7 requires a hydraulic pressure test on R600a in the type approval for 1 min. without any leakage with 35bar rel. on high pressure side si de and with 10 bar on low pressure press ure side. See chapter 10.17.

Pressure tests.

We recommend, if possible, executing pressure test on all R600a refrigerator during production at time of Helium leak test at 35 bar respective 10bar to stress brazed joints and to reduce leaks and returns from the market. But pay attention: flat aluminium (Roll Bond) or copper parts (accumulators, receivers) could deform by such pressure on samples. So a compromise must be made.

8.5.3.

Leak Simulation Test of Refrigerators Charged with Hydrocarbon

Electric components and cooling circuits must be separated by construction (see our chapter 8.2.-8.3.) and the separation tested by leak simulation tests for type approval. We have to execute such tests for 3 different groups of appliances: 1. Appliances with protected hydrocarbon charged cooling systems without any part of the cooling system inside the food storage compartment, but with electrical components which do not comply with the IEC 600079-15 requirements (“n” protection, IP54); 2. Appliances with protected hydrocarbon charged cooling systems where the cooling circuit parts located inside the food compartment are constructed with an additional at least double layer, each of min. 0.1 mm thickness; the bounded seams must have a minimum width of 6mm; or the cooling system inside the food compartment is built into a separate enclosure; in both cases the food compartment contain electrical components which do not comply with the IEC 600079-15 requirements ("n” protection, IP54); item 2 is practically not used; 3. Appliances without protected hydrocarbon charged cooling systems where the unprotected electrical components (thermostat, light switch, light etc. are relocated outside the cooling department in areas supposed to be free of refrigerants in case of leakage. In all these cases leakage have to be simulated and the Hydrocarbon concentration to be measured near electric components by Hydrocarbon leak detectors. IEC/EN600335-2-24 in clause 22.107 describes test of protected cooling circuits in combination with unprotected electrical components which can cause arcs, sparks or hot surfaces while clause 22.108 describes test of unprotected cooling circuits in combination with “n” protected electrical components (IEC/EN 600079-15 n protection; IEC/EN 60335-2-24 Annex CC), certified by component manufacturers, inside food compartment and clause 22.109 the test of standard electrical components allocated to outside food compartment, if their location cannot anymore be reached by leaking refrigerant.


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The leak simulation should be made from all critical points. All interconnecting points are considered as critical points as well as locations of a capillary tube which can be destroyed mechanically. At these points the leak has to be simulated through a capillary tube of 0.7 +/- 0.05 mm and 2-3 m length. In case a joint is foamed in also the leak capillary tube has to be foamed in, but in a way that the tube will not be blocked by foam. 80% of the nominal charge of appliances should be injected or the maximum which can be injected inside of 1 hour. Doors and lids should be closed during test to check if hazardous gas can be accumulating inside the compartment. The gas should be taken from the vapour side of a bottle with a temperature of 32 +/-1 °C if leakages are simulated on low pressure side and 70 +/- 1 °C if leakage is simulated on the high side pressure circuit. At the end of the test there must be liquid refrigerant left in the bottle. In case of blends this test has to be executed with the fraction which has the lowest LEL value. The instrument which measures the gas concentration, like calibrated infrared sensors, gas chromatographs or mass spectrometer should have a reaction time of max. 3 sec. and sampling should be take at least every 30 s inside and outside the compartment near electrical components for 1 h after injection of gas has stopped. Sampling must be limited to maximum 2 ml every 30 sec. not to influence test results (on/off valve on inlet to gas chromatograph or mass spectrometer; if Inficon Ecotec is used, remove capillary flow alarm setting during such tests). Best are IR sensors with gas flow control and return of sampling gas into the area, from which gas was taken (Dräger PIR 7000 Type 334 with gas probe inlet and return system IWS). The measured value value should not exceed 75 % of the LEL of the refrigerant and 50% of the LEL for a period exceeding 5 min. to pass this test. 30 min. after gas injection into close compartment is finished the door or lid is opened by 90° for 2-4s every 30s. Separate components such as thermostats which contain less than 0.5g of flammable refrigerant are not considered to cause a fire or explosion hazard in the event of a leakage of the component co mponent itself acc. to the standard IEC 600335-2-24.

8.5.4. Scratch Test of Refrigerators Charged with Hydrocarbon in addition a scratch test have to be applied on all accessible surfaces according to standard IEC600335-2-24 section 22-107.2 with tools described in Figure 102 with specified parameters and criteria of pass and fail, which we will not repeat hear as it is described in this standard. We do not recommend such solutions for cost reasons, as it is avoidable. On multi-layer cooling circuit systems

8.5.5. Testing of standard electric components not reachable by flammable Refrigerant Sparking electric components can be positioned for example in refrigerator top. In a type test it has to be checked that no flammable refrigerant can touch such electric item according to IEC60335-2-24 clause 22.109 or IEC60335-2-89 clause 22.108. The test is performed in a dr draught-free aught-free location with the appliance switched off or on (first run without powering the electric part to be tested) whichever gives the more more unfavourable result. A quantity equal to 50 % of the refrigerant r efrigerant charge ±1,5 g is injected in a draught-free location from the nearest external pipework joint to the electric component to be tested into the considered area over a period of 1h in constant consta nt rate. Sample: Let’s suppose the charge of the model to

be tested is 120g R600a. In this case we have to inject 1g/min. If the R600a bottle is inserted into an ice-water bath (0°C) (0 °C) on a balance R600a gas phase pressure is 0,57bar rel., the gas volume is 0,232l/g and we need a flow rate of 0,232l/min.=1g/min on scale to be calculated (see chapter 4.1.) and tested using adequate capillary tube diameter and length. Such test records should be stored to adapt capillary tubes lengths to other rates r ates for other models. The concentration of leaked refrigerant as close as possible to the electrical component is measured at least every 30 s by IR gas sensors from the beginning of the test until 15 min after a sustained decrease is observed. The measured value shall not exceed 75 % of the lower explosive limit of the t he refrigerant as specified in above table about LEL LE L values of R600a or R290, and shall not exceed 50 % of the lower explosive limit of the t he refrigerant as specified in this LEL table for a period exceeding 5 min.


8.5.6. Testing and Control of "N” Protected Components Used in Hydrocarbon Leak Areas

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Electrical

In cases where electric components are placed in areas in which potential leaks can happen or in which the a.m. appliances could not pass the leak simulation tests or the scratch test the electric components must fulfil the requirement of IEC IE C 60079-15 with the protection “n”. Refrigerator producers have to insist on their suppliers of these electrical components components to receive at least a declaration of conformity for the component and, better, test reports of a good, internationally reputed test institute. In case of any doubts it is better to insist of another independent test report or to replace such items by ones without any reserves. If the refrigerator manufacturer has a well equipped laboratory he can do such tests according to IEC600079-15 himself.

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9. TEMPERATURE CONTROL Different types and kinds of temperature controls can b e used to control the operation of refrigerators and a nd freezers.

9.1. Capillary Tube Thermostat Most common types of temperature controls are electromechanical thermostats using a mainly vapour filled capillary tube as temperature sensor: A temperature change causes a pressure change of the fill. This change is converted to a travel via a diaphragm or corrugated tube, actuated by a lever system which mechanically closes a switch on temperature rise above a set value and opens the switch again on temperature fall underneath a set value. Following terms are used: The operating range of a thermostat describes the temperature range in which the thermostat can operate. The whole needed temperature ranges in the household refrigerator section cannot be covered by one control type only, so different types working with different ranges are needed. Operating range.

A mayor group of thermostatic controls are adjustable inside their operating ranges. The adjustment range is the difference between the cut-in point in warmest control positions to cut-in point in coldest control position. There exist some exceptions used in chest freezers with a constant cut-in feature. In such a case the adjustment range is the difference from cut-out point in warmest control position to cut-out point in coldest control position. The 2 temperature values of cut-in temperature range and the 2 of the cut-out temperature range are normally printed on the thermostat casing. Adjustment range.

Switching differential.

The switching differential is the difference between cut-in and cut-out point of the temperature control.

There a certain correlation between adjustment range and switching differential, i.e. the indicated limits cannot be assigned optionally. Correlation between adjustment range and switching differential.

Tolerances. There exists a permissible deviation from fro m nominal operating point.

The temperature control is set in the thermostat factory according to specified temperature values. In the refrigerator factory adjustments never should be made at the switch differential screw, but only on the range screw or the temperature screw: Such an adjustment will change the cut-in and cut-out value to be shifted in direction of cold or warm, but not the switch differential, if a standard thermostat is used which allows adjustment on the cut-in position. In case of a thermostat with constant cut-in is used, such adjustment will change the cut-out position and therefore in Adjustments in the refrigerator factory and in the service.

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addition the temperature differential. The new set point must be temperature controlled to ensure the correct operation of the thermostat. Temperature controls are available with and without OFF-position. The OFF-position will interrupt the operation even when the temperature is above the cut-in position. OFF-position.

It seems that all manufacturers of adjustable capillary tube thermostats for household refrigerators follow the same dial layout: - A clockwise rotation of the dial shaft causes colder control settings. - The standard dial angles are the following: - Total adjustable range: 270 ° - Dead angle: For thermostats without OFF positions: 90 ° For thermostats with OFF position 45° and OFF position at 45 ° Dial layout.

Following types of thermostats used for household refrigerators are on the market:

9.1.1. Standard Thermostat Typical function chart

Typical Electrical Wiring diagram

Such standard types execute only simple cut-in and cut-out operations. They are used for simple refrigerators and freezers, automotive air conditioners and other appliances. Such thermostats can be made adjustable with a spindle and dial knob or for fixed temperature values without such a knob. Adjustment range is normally from 5 °C to 20°C

inside the operation range of -40 °C to +15 °C.

9.1.2. Thermostat with Auxiliary Switch Typical Electrical Wiring diagram

Typical function chart

Such types are the same as the first ones, but have in addition an auxiliary switch (terminal 3-6) connected in series with the main switch which breaks the current circuit as soon as the temperature control is set to OFF position The function of this thermostat is the same as the last one. But an electrical heater can be added on terminal (6) to allow heating at OFF-position of the thermostat.

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9.1.3.

Thermostat with Heater Contact



Such types are more used in ice makers and air conditioners.

The function of this thermostat is the same as the last one. But an electrical heater can be added on terminal (6) to allow heating at OFF-position of the thermostat.

9.1.4. Thermostat with Signal Contacts Typical function chart

Typical Electrical Wiring diagrams

Such types are used in freezers. The function of this thermostat is the same as the first one. But in addition to the cut-in and -out switches a contact for a warning signal lamp is closed in case of higher temperature. In addition it is possible to get an operation signal if needed.

9.1.5. Thermostat with Semi-Automatic Defrost Push-Button Typical function chart


Such types are used in some refrigerator types. The function of this thermostat is the same as the first one. But in addition to the cut-in and –out switches a push-button for semiautomatic defrost function is added to allow a manually initiated automatic defrost cycle. By initiating the defrost the main switch is opened and later automatically closed when the set defrost temperature, normally +6 °C (between +2 and +10°C possible) in reached.

9.1.6. Thermostat with Fast Freeze Typical function chart

Typical Electrical Wiring diagrams Such types are used in today in vertical freezers and deep freezers .

The function of this thermostat is the same as the 3rd one with signal lamp. But in addition there exists an auxiliary function to initiate fast-freeze/deepfreeze cycle till a specified temperature value is reached by actuating the pressure pin or a bush-button signal lamp. The specific fast freeze

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temperature value can be fixed separately or parallel with the cut-off characteristic of the thermostat. The main switch is manually locked with starting the fast freeze cycle and if the fast freeze temperature is reached, the system automatically resets this lock, so that the system will go back to the standard cut-in cut-off control. In addition a manually reset is possible by turning the dial shaft to OFF position.

9.1.7. Thermostat with Fixed Cut-In Temperature Typical function chart


Such types are used today in refrigerators and 2 door fridgefreezers, controlled only by the temperature of the refrigerator. In such systems the cut-out temperature can be adjusted, but the cut-in temperature which is above 0 °C remains fixed. During cut-offs the refrigerator evaporator defrosts and the water is drained to the outside normally on a tray above the compressor. The defrosting can be made by natural temperature increase (used normally in standard defrost models) or even by a heater on the evaporator (used in No frost models) during the stand still time of the compressor. When the thermostat is switched off the electricity can pass the heater and the compressor coil. Because of the ratio of resistances in the heater and compressor coil the power is mainly used in the heat resistance and not in the coil. In this case it is necessary that the heater is not switched off in the OFF position of the thermostat. Therefore another terminal on the thermostat is needed. The last wiring diagram shows a version which allow a separate switch s witch off of the defrost heater.

9.1.8. Thermostat with a 3 Ways Solenoid Valve Control Such types are used in 2 door fridge-freezers, equipped with one compressor but 2 separate refrigeration cycles for the refrigerating and the freezing part. The system controls a 3 ways solenoid valve. Typical function chart


Terminal 2-3 opens at temperature rise. Terminal 3-4 closes at temperature rise. Terminal 3-6 opens in OFF position. This type comprises all features of the last type; but with an so called SPDT switch instead of an SPST switch between the terminals 23 a solenoid 3 way valve can be switched to control in function of the refrigerating part temperature and with that the refrigeration cycle to the evaporator of the freezing or of the freezing and refrigeration part. Further details can be granted from Danfoss about Thermostat type 077B63 and their 3 way valve or from Ranco about thermostat type K61.

9.1.9. Thermostat with 2 Sensors Typical Electrical Wiring diagram


There exist also thermostats with 2 capillary tube sensors. Sensor A normally fixed on the evaporator taking over the cut-in function and a nd sensor B normally placed in the inside the cut-out function. The advantage among others can be energy savings, almost unaffected control temperature in the *** freezing and refrigerating compartment at ambient temperature changes between + 15 °C

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and +32°C. There are different versions with fixed cut-in or with adjustable cut-in. Even a version with crossing cut-in and cutout exists.

9.2. Bimetal Thermostat American and Japanese refrigerator producers use in their No Frost bimetal thermostats. Their dimensions are very small. But their functions and applications are still limited comparable with adjustable capillary thermostats.

9.3. Electronic Controls and Thermocouples Nowadays more and more electronic controls are developed for freezers and fridge freezers to improve the control on frozen food and to reduce the power consumption. With an electronic device sophisticated controls can be executed. With Fuzzy logic, ASICS, EEPROMS, compressor speed control (see chapter 2.10. Variable capacity compressor) further important parameters can be controlled in a way that the system can be much better adjusted to the actual environment, temperature needs and conditions. In such cases temperature are measured by cheap thermocouples instead of mechanical thermostats. Warning buzzers, temperature LCD displays, LED’s, electronic timers verbal speech etc. can be easier integrated as with conventional methods. Price wise such systems became more and more comparable with conventional electromechanical controls as long as similar features are compared. The cost of an electronic temperature control for a fridge-freezer with a light switch combination and a visual and acoustical warning signal are nowadays not more expensive as the same in an electromechanical version, if it is produced in large scale. But electronics allow much more features and controls to be added. In areas with bad electrical supply conditions electronic controls are not as reliable as the electromechanical controls used in the past, but also this can change in the future. With an electronic control additional controls and operation modes can be realized, like: -

“Child safe” Switch-off : 3sec activation of ON/OFF push button SuperCool (only with electronic control). The SuperCool function reduces the fridge temperature for

6h to +2°C after

shopping to speed up cooling of higher fresh fres h food charges. SuperFrost. In SuperFrost mode (often push button with lamp) the temperature of food to be frozen are stronger pulled down to a temperature same or even deeper than the normal cut-off (last only in electronic control), to preserve vitamins, minerals and aromas in food, in No Frost models with increase ventilation speed. DuraFreeze (only with electronic control and variable speed compressor). The DuraFreeze can be switched on if needed, to reduce temperature of freezer to -28°C, which doubles the freezer storage time, preserve the taste, aromas, vitamins and minerals. SuperFrost push button with lamp (permanent run till a fixed temperature, which can be different from the normal cutoff, is reached) and in case of No Frost with increase Ventilation speed Holiday is a mode to run only the freezer. The T he refrigerator part is emptied and their temperature te mperature kept on +15°C with closed door to avoid any bad odours and mold. LCD display control with actual temperature measured by cheap thermocouples instead of capillary thermometers and programmed temperature in refrigerator and freezer, operation mode display in clears words (SuperCool, SuperFrost, DuraFrost, Holiday etc.) Fuzzy logic for extended controls like SuperCool after Shopping (time temperature controlled permanent run for about 6h at +2°C in case of high new load after shopping. “Frostmatic” (time temperature controlled permanent run for about 24-52h in case of high new load of minimum 4,5kg/100l load), and in case of No Frost with increase Ventilation speed Warning buzzers or voice Temperature too high, if compressor don’t start and temperature still increase above set value Warning buzzers Doors not closed or voice Please close door in different languages. No-frost freezer defrost control. To save energy the defrosting of evaporator coil is not made by timer 3-4 times t imes per day but by defrost temperature control to switch on and off the heating. rd Temperature zone near 0°C as 3 compartments. If in addition a storage temperature near to 0°C (0°…+3°C or even -3°C…*3°C) can be reached

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instead of 5°…8°C fresh meat, fish, milk products, vegetables and fruits remain 2-3 times ti mes longer fresh, keeps 3 times longer taste, aromas, vitamins and minerals. This can be realized with a 3 door model, a 2 door model with movable or not movable inner insulation separators. The different temperature zones ( 5-12°C, 0-3°, >18°C) can be kept already by evaporator and insulation designs without separate temperature controls up to a certain deviation range or - very accurate - by temperature controls on each zones zones with refrigerant valve or separate circuits and compressors (expensive solution). But such 3 temperature zone models will consume more energy as a 2-door (2-temperature) model, a part of fridge remain on -1°-3°C temperature while in the past only o nly on 5-8°C. Even a temperature range of -3°C for fish, -1°C for meat, +2°C vegetables and fruits would be best, but it needs in this case a separate temperature te mperature control on this food storage part which can be easier and cheaper realized by an electronic control. T his temperature zones are under freshness of food a very relevant aspect, but still s till not enough reflected in the Energy labelling system s ystem as it needs this additional model group to be compared and not to be compared co mpared with standard fridge-freezers. Ice and Water Spender . On side-by side models it is today’s standard. It is sold as lifestyle product (party house bar). The operation needs further controls which can be integrated into the electronic control (temperature, levels, refilling of ice maker by tap water, if as often done the refrigerator refri gerator is connected to tap water). Control of variable compressor speed . If a variable compressor is mounted the speed control can be integrated into the electronic control to let the compressor run r un according to temperatures and load conditions. This often can save 2033% of energy in comparison to conventional compressors with 1 speed to reach energy saving models (A+, ( A+, A++).

9.4. Special Controls for NO-Frost Models No frost models need special controls to execute automatic defrost on the coil evaporator.

9.4.1. Defrost Timer and Thermostat The simplest way is to start the defrost cycle and to heat the evaporator by a timer, for examples 3-4 times per day. To reduce energy consumption the defrost cycle should be stopped when the ice is removed, which could be measured by a defrost thermostat on the evaporator. In a multiple evaporator system defrosting by a reverse valve or by using thermosyphon effects is less energy consuming as electrical heaters (see chapter 5.5.6.).

9.4.2 Damper Thermostat Standard No Frost fridge-freezers controlled only by one thermostat in the refrigerator are consuming much more energy than systems which keeps control on the reached temperatures in both compartments. A simple possibility to optimise such a system is to introduce in the air channel a damper thermostat which distributes the cold air flow between the freezer and the refrigerator according to the needs.

9.5. Testing of Temperature Controls The settings of temperature controls should be b e tested by random system in the following way: -

The dial shaft should be positioned on test position; The temperature feelers of a same group of temperature controls should be dipped in a well circulated water bath; the min. depth of immersion of a capillary tube feeler is i s 160mm; Before recording the actual operating points, 2-3 no-load c ycles of on and off switching have to be executed; The temperature change in the bath should be 0.5 °K/min. Near the on and off point respective the signal point, i f any, if necessary, barometric corrections have to be calculated. Normally gas filled capillary tube sensors work in the range of 0600m above sea level with the deviation of +/-0.6 °C (reference point is 736,6 mm Hg= 0.98 bar = about 263m above sea). On 1500m we aspect about 634 mm Hg and on 300m about 526 mm Hg. That means that a vapour -filled thermostat with a

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cut-in temperature of -20 °C (at 736.6 mm Hg) will cut-in already on a 2+/-0.5 ° at 1500m respective a 4 +/-0.5 °K at 3000m lower temperature as calibrated, depending with which gas it is filled. All temperature switch settings of a system should be tested in this way. In addition electrical tests should be executed, like current (6A on main contact, 0.1 on signal contact) flash test 0-400Vac (0-180 sec), normally at 1000Vac, insulation test and electric strength 500Vdc (0-180 sec) 3-50 MOhm, M Ohm, depending which temperature control is used. The supplier of temperature control should guarantee a maximum failure rate of 0.7% and the measured rate should be in the range of 0.5% and not higher. To allow replacement already after the performance test inside the factory and in case of service, the feeler should be place in a plastic tube when it will be foamed in to allow the exchange of the unit.

Modern energy saving refrigerators for N and SN climate class need several hours for cut-off after first time of refrigerator running and often 1-2 days to cut-in again with closed doors, so the thermostat of all refrigerators cannot be tested by the short performance test and even not by the 2-4h performance test on samples. But up to 0,7 % is already a high failure rate of such temperature controls and cost relevant for maintenance service during guarantee – beside of damage of trade mark by such a failure. Therefore good refrigerator manufacturers control cut-in and cut-off functioning and temperatures of 100% of used thermostats to reduce these high guarantee costs. We strongly recommend to do such 100% test - best inside factory of supplier of such controls, so that statistical sampling and and additional control tests inside the refrigerator factory are sufficient - and to establish mounting and handling precautions to prevent damage of such thermostats during assembly. 100% control on temperature control device.

Relevant remarks in operation manual of f ridge/freezers with single temperature sensor control: Freezer defrosts in a fridge/freezer. In a cold location the freezer may begin to defrost or even completely defrost, so defrosted frozen food will spoil. Most fridge freezers will only operate satisfactorily in an ambient temperature down to +10 °C, if made for SN climate class, or +18°C if made for N climate class (see chapter 1.3.2.). This may seem strange but the fridge thermostat governs the operation of the freezer and if the ambient temperature drops to either of the figures above the fridge will switch off. That will not be a problem for the fridge which should be cool enough to keep its contents safe but it will mean that the freezer will cease to work and that will create a problem. Therefore the customer should be warned in the operation manual or by a warning sign to insure ins ure minimum ambient temperature to ensure functioning of freezer.

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10. FINAL TESTS In previous chapters we have described tests to be executed to optimise each single refrigeration circuit element separately, like -

cabinet constant test to determine the thermal losses (chapter 1.4.2), foam insulation tests (chapter 1.5.2), testing of the air tightness of door and lid seals (chapter 1.5.3), calorimetric tests to optimise compressors (chapter 2.), condensers

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pull down tests (chapter 5.2.1, 5.4.1) capillary tests (chapter 4.2.), refrigerant and circuit components purity and cleanliness tests (chapter 7.2.) refrigerant charge quantity tests and fine tuning (chapter 7.4.), electrical safety tests (chapter 8.5.), temperature control tests (chapter 9.5.).

(chapter 3.6.), heat exchangers or evaporators (same

like chapter 3.6.; chapter 5.3.),

In this chapter we will describe the final tests to be executed to optimise a refrigerator and/or freezer circuit after each circuit element was already optimised and tested and tests to be executed according to the applied standards. Many final tests to be executed are described in the a.m. ISO standard 15502, which replaces ISO 7371, 5155, 8187, like -

Testing of reached temperatures in the refrigerator and freezers Testing of storage temperatures Water vapour condensation test Energy consumption test Ice making test Test of percentage running time Temperature rise time (freezer) Freezing test (freezer)

The relevant standards are describing these tests in all needed details so that we have not to repeat them in this chapter in all details.

10.1. Definitions, Classifications, Designs and Characteristics The ISO standard 15502 for household refrigerators (previous ISO 7371), fridge freezers (previous ISO 8187) and freezers (previous ISO 5155) describe all relevant definitions, classifications and characteristics in their first chapters: the appliances and important parts of them are defined and classified, the used materials, design and manufacturing, the required characteristics, the volumes, areas and performances. Also the method method how to measure the dimensions and volumes are determined (for details see these standards). Furthermore these standards describe general test conditions, the test room, the used Tylose test packages, the measurement means, where and how to measure the temperatures and the test period. The test period must be minimum 24h. The 24h test period must be prolonged to 48h if there is inside ins ide the first 24h not a single sin gle defrost period. Test conditions and periods.

Under given conditions of ambient temperature and internal storage temperatures is the percentage of running time R for the appliance with on/off control the ratio r atio Percentage running time.

where

R = d/D *100

d = the duration of the refrigerating system operation during the whole number of cycles; D = the whole duration of cycles.

For 2 temperature storage with 2 independent systems 2 R values have to be determined.

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10.2. Refrigerator Test Room In this chapter we describe a test room specification and requirements according to the established standards for test rooms (DIN 8953 draft 1987, ISO/DP 5155 and American standard B 149.1 AHAM/ANSI DH 1-1986). The proposed equipment and their specification will allow testing refrigerators and freezers according to a wide variation of condition, established standards and power supplies existing in countries all over the world. For limited market with smaller variation of conditions, the full range of condition variations are often not needed and can be reduced for cost reasons, if the customer wants.

10.2.1. Thermo-Insulated Test Room To be able to test refrigerator and freezer cabinets with up to 1800mm height, 800mm width and 800mm depth, and chest freezers with up to 800mm depth the test room should have minimum following inner dimensions: 2400mm height, 2400mm width and 4000mm length. The door should have the dimensions of 2100mm height and 1000mm width and placed in a way that freezers and refrigerators can be transported tr ansported from and to the test room without removing r emoving a 2nd refrigerator.

Dimensions.

Light. Light intensity 500 lux measured 1

m above the floor.

Supply. The test room needs following fo llowing service supplies:

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Cold and hot water (also for humidifying plant) Air (low pressure) Drain from the vacuum pump Drain channel Voltage supply of 220V and 50 Hz, 115V and 60 Hz, and 3x 380V, 50 Hz (three phases current).

The test room's temperature should be adjustable to constant values in the range of 10 till 48 °C. The maximum deviation from the set value is +/- 0,3K from the constant value and from the varying heat load in the room (intermitting operation). The demands must be met by b y the measurement object for the following heat emissions:

Regulation ranges .

Q (constant) = 50 - 900W Q (variable) = 0 - 500W (max.) and 0 - 50W (min.) The relative humidity must be adjustable in the range of 40-90% relative by +/- 5% in the a.m. regulation range for test temperatures. Such heating and air conditioning equipment including humidifier/dehumidifier can be purchased, for example from Danfoss with requested regulations. The ventilation of the room must be placed in a way that the natural air circulation around the cabinet and the refrigeration system is not obstructed. the max. permissible air speed according to the ISO and DIN standard is 0,25m/sec. The American standard allows only 0,2m/sec. To fit the a.m. voltages and frequencies it is necessary to have a frequency converter from 50 to 60 Hz with control and a voltage regulator and control

Voltage regulator and frequency converter.

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Nominal voltage and frequency outputs (U n) are: - 230 V 50 Hz Hz - 230 V 60 Hz - 240 V 50 Hz - 110 V 50 Hz Hz - 115 V 60 Hz Hz with a regulation range: +/- 20%. The max. voltage and frequency deviation allowed is +/- 1%. The max. allowed main impedance is: - for 110 V and 115 V: -0,4V/A and - for 220 V and 230V: -0,4V/A. Loads and supply places . Following loads and supply places are

needed:

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Measurement object: 1,2 kW Auxiliary functions: 1,0 kW Co sinus phi: 0,6-1,0.

Starting current . Following starting currents are needed:

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At Un = 110 V and 115 V: 36 A At Un = 220 V and 230 V: 18 A

Voltage, Ampere and frequency supply flow chart

Refrigerator Test Room Data Recording Scheme Power Supply

VarioTranformer 110-250V

50-60HZ Generator

Control Panel

Thermoregulated Room Refrigerator to be tested Plug Box Bo x Thermocouples

Wh, V, A, Cos Phi, Hz

Monitor

Printer/ Plotter

Personal Computer

Electrical Data Interface

Temperatures

Thermoregulator

Terminal Board Humidity sensor Thermocouple

See Transfair Engineering: Refrigerator Test Room Equipment and Manuals. Düsseldorf 2000

Analog-Digital Data Logger

10.2.2. Measurement Equipment Energy measurement.

measurement object.

The installation must contain kWh-meters for the measurement of the energy consumption to the

The meters must be provided with revolution counters in order for the data collection equipment to register the actual energy consumption. The accuracy should be 1% at nominal voltage and frequency. The power consumption (W) measurement by built in transducers (without measuring of secondary supplies) should be in the range of 100-1200W (co sinus phi: 0,6-1,0) with an accuracy of +/- 5% of the actual value. The signal of the transducer should be transferred to the data collecting equipment. Power consumption measurement.

Transducers are to be installed for measuring power to measurement object under the before mentioned conditions with accuracy of +/- 1 % of the actual value. The signal has to be transferred to the data collecting equipment.

Power measurement.

Transducers are to be mounted for voltage measuring to the measuring object. The measuring ranges are 90 V -255 V with +/- 0,5 % accuracy of the actual value. The signal has to be transferred to the data collecting equipment. Voltage measurement.

For some electrical tests ampere and power converters, vario and current transformer and frequency, voltage and Ampere meters and digital temperature meters are useful. Further electrical tests.

For testing the compressor a clamp tester (Refco Art. No. WM 150) and a test cord (Refco Art. No. 13575) to bridge the thermostat switch are needed. Further units can be made locally. This panel should have following facilities: Digital voltmeter to display actual voltage of the measurement objects Equipment for the regulation of voltage to the measurement obj ect Switch for start and stop of measurement object Digital display for passed time and relative operation time of the measured object Switch for manual cut-in and cut-off of the kWh meters

Control panel (outside test room).

-


p. 111

- Electronic counters with BCD outlet for measuring speed (rev./min) o n kWh meters All or parts of it can be integrated i ntegrated in a registration programme instead of the control panel. Inside the test room on the backside wall there should be positioned a panel to connect the measurement signals and the power supply to the refrigerator(s). re frigerator(s). This panel should have following facilities: - Voltage supply - Connection for 2 pcs. pressure transducers (for example Hottinger & Baldwin type PM3) - Connection of minimum 16 pcs. thermo-elements cu/ko (for example type T specifications according to ANSI 96.1.82 or type J) with standardised plugs and plug sockets so ckets should be chosen. - 8 digital inputs (8 signals, 170-270 V, 50 and 60Hz; 60-140 V, 50 and 60 Hz). - Option: 8 digital outputs (8 signals, 220 V, 50 Hz; max load 1A). Connection panel (inside test room).

10.2.3. Measurement Ranges and Accuracy -50 < t < + 200 °C +/- 0,5 in the range -25 < t < 50 °C +/- 0,75 in the range -50 < t < -25 °C and 50 < t < 200 °C. -1 < P < 10 bar 1 < P < 20 bar 1 < P < 50 bar +/- 1,0% of measured value

Temperature:

Range: Accuracy:

Pressure:

Range 1: Range 2: Range 3: Accuracy

Power:

Range: 0 - 1200 W Accuracy: +/- 0,5% of measured value Range 1: 0 - 10 A at Un = 110 and 115 V, 50 and 60 Hz Range 2: 0 - .5 A at Un = 220 and 230 V, 50 and 60 Hz Accuracy: +/- 1% of measured value Measurement with approved gauges in the a.m. range of power and current and the accuracy of 1% at actual load. Range 1: 170-270 V, 50 and 60 Hz Range 2: 60-140 V, 50 and 60 Hz Accuracy: +/- 0,5% of measured value.

Current:

Energy: Voltage:

The selected Voltages and Frequencies depend for which market the refrigerators are developed. There are different ways possible to register the measured temperatures, pressures, humidity and electrical data and to register it.

10.2.4. Test Data Loggers, Recording and and Evaluation Today A/D interfaces on PCs are used to test refrigerators and to record test data (pull down temperatures,, high and low pressures, humidity, electric power absortion, cos phi, etc. The quantity of measurement channel channel per test place and session depends on the models to be testedTo permit preparation and execution of 2 or 3 independently recorded tests it is much more convenient to use 2-3 interfaces each of 8 channels for simpler units up to 30 channels for Coca-cola or Pepsi cola vendors, to be registered into PC. Such a system consists of the following: following: -

1 pce with actual Intel or AMD processor, pr ocessor, large hard disk, colour display, USB and serial ports; 2 pce A/D interface each with at least 8 analogue analogue input channels and 1 digital input (8 signals, 60-270 V; 50-60 Hz); Option: 1 pce. Digital/analogue output; 1pce colour printer; 1 pce data recording and evaluation software like AMR measurement software; 16 temperature transducers: thermo-elements like type T (Cu/Ko) (Cu/Ko) or K (NiCr-Ni) specification according to ANSI standard 96.1.82/1; 2 pcs. pressure transducers for example 1 pce -1/ +2 bar; 1 pce 0/20 bar or higher if needed from refrigerant side; 1 pce power transducer 0-1200W; +/- 0,5% or higher if needed from model side; 1 pce. current transducer 0-10 A; +/- 1% or o r higher if needed from model side; 1 pce. energy transducer (0- 1200 W; 0-10A or higher if needed from model side):


-

p. 112

1 pce voltage transducer (60-270 V, 50-60 Hz).

Max. load for all a.m. transducers transducers are: max. = 36 A for for 5 sec. Un = 110 V/115 V and 50/60 Hz or max = 18 A for 5 sec. at Un = 220/230 V and 50/60 Hz This equipment is normally sufficient to measure 2 refrigerators or freezers for designing and optimisation purpose independently from each other. For performance tests to control the reached quality of the production the same equipment can be used; but in this case more refrigerators can be measured parallel, only limited by the measurement channels (each proposed interface has 8 analogue inputs, 2 units 16, 3 units 24 channels etc.). Transfair has developed such computerised measurement hard- and soft ware by combining reliable and cheap standard components. See Transfair Engineering: Refrigerator Test Room Equipment and Manuals – Description, Manuals, Technical Documentation. Düsseldorf Düsseldorf 2000 .

10.2.6 Test Packages For all the 3 methods of performance perfor mance tests following test packages which simulate lean meat have to be added: 350 kg Tylose test packages 200x100x50mm (1kg each package)) 150 kg Tylose test packages 100x100x50mm (0.5 kg each package) 50 kg Tylose test packages with thermocouples in geometric centre 200x100x50mm (M-Package of 1kg each) 50 kg Tylose test packages with thermocouples in geometric centre 100x100x50mm (M-Package of 0.5 kg each)

10.3. Mechanical Tests Several mechanical tests have to be applied on the household refrigerators and freezers, concerning: - air tightness of door and lid seals , - opening force of the doors and lids , - durability of hinges and handles, - mechanical strength of shelves and similar components.

Details for executing these tests can be taken from the standards.

10.4. Testing of Storage Temperature The purpose of this test is to check if the appliance fulfils the storage temperature requirements under the ambient temperature of the selected climate class. How to prepare the appliance, how to storage the food into the freezer and where to position the temperature probes are described in ISO standard 15502 (under chapter 13 of previously valid ISO 7371, 5155, 8187.

10.5. Water Vapour Condensation Test The Water vapour condensation test is made to determine the extend of condensation of water on the external surface of the cabinet under specific ambient conditions and humidity. The test conditions and procedures are described in chapter 14 of these standards.

Transfair Engineering: Engineering: Designing …Cooling Circuits. 10. Final Tests, Mechanical, Storage Temperature, Water Vapour, Energy Consumption, Temp.rise p. 113

10.6. Energy Consumption Test and Labelling The energy consumption test tests the energy consumption (W/24h) of an appliance over a period of 24h running under stable conditions at the ambient temperature for which the appliance was designed for (Climate class N, ST, T with 32 °C 38°C or 43°C). How to execute this test can be taken from ISO standard 15502 (chapter 15 of ISO 7371, 5155, 8187) and in Europe it has to follow EN153 (2006) for classification in group A-G (see Annex).

10.6.1. Energy labelling system To reduce energy consumption many countries have introduced energy consumption labelling s ystems for household products in which the groups of household equipment on each market are compared with each other concerning their energy consumption. Many countries (EU and neighbour countries, USA, Canada, J apan, Korea have agreed of labelling classes A to G. In Eur ope the labelling system is according to EU rules 94/2/EC amended with 2003/66/EC (by introducing A+A++ classes) and the te st procedure to be applied is according to the EU standard sta ndard EN 153 (1996, revised prEN153 2005) and will be checked once per year (see Annex).

10.6.2. Calculation of EU Energy Label Efficiency classes For cold-appliances the efficiency class grades A to G were defined for each product category in terms of an energy efficiency index I (defined as the tested model electricity consumption divided by the prescribed "average" model consumption for a unit of the same adjusted volume) as given in Table 1. Table 1: Relative efficiency grades used in t he EU energy label for cold-appliances Energy Efficiency Energy Calculations: Index Iα Efficiency Class Iα=AC/SCa *100 30>Iα A++ where: AC= annual energy consumption of appliance A+ 42>Iα≥30 SCa= standard annual energy consumption a of appliance A 42>Iα≥55

0.55
α

α α

α

α

B C D E F G

Completely Phased out in EU 2004

SCa= Ma * Σ (Vc *(25-Tc)/20 *FF*CC*BI) + N a *+ CH

where:

Vc is the net volume [l] of compartment co mpartment Tc is the design temperature [°C] of the compartment Ma and Na values see table 2 FF, CC, BI and CH values see table 3

Thus, a G class model uses 125% or more energy of an "average" cold-appliance of the same t ype and the same adjusted volume, while an A class model uses less than 55% of an average appliance of the same type and adjusted volume. The energy consumed by an average appliance of a given type and adjusted volume is calculated fro m the appropriate average performance reference line equation given in Table 1 and based on the values measured under the norm EN 153. Table 2: Type of appliance and Ma and Na factor values Type of appliance

1 2 3 4 5 6 7 8 9 10

Larger Fridge Refrigerator/chiller Refrigerator no star Refrigerator * Refrigerator ** Refrigerator ***/ Fridge-freezer *(***) Upright freezer Chest freezer Multi-door or other appliance

Temperature of coldest compartment

> – 6 °C > – 6 °C > – 6 °C ≤ – 6 °C * ≤ – 12 °C ** ≤ – 18 °C ***/*(***) ≤ – 18 °C ***/*(***) ≤ – 18 °C *(***) ≤ – 18 °C *(***)

Mα

Nα

0,233 0,233 0,233 0,643 0,450 0,777 0,777 0,539 0,472 (1)

245 245 245 191 245 303 303 315 286 (1)


(1) For these appliances, the temperature and star rating o f the compartment with the lowest temperature will determine the values of M and N. Appliances with – 18 °C *(***) compartments shall be considered as fridge-freezers *(***). Table 3: Correction factor Correction factor Value

FF (frost-free) CC (climate class)

BI (built-in) CH (chill compartment)

1,2 1 1,2 1,1 1 1,2 1 50 Kwh/y 0

Condition

For “frost-free” (ventilated) frozen food compartments Otherwise For “tropical” appliances For “subtropical” appliances Otherwise For built-in appliances (1) of under 58 cm in width. Otherwise For appliances with a chill compartment of at least 15 litres Otherwise

(1) An appliance is “built-in” only if it is designed exclusively for installation within a kitchen cavity with a need of furniture finishing, and tested as such.

The revised version EN153 2006 as result of new EN 15502 (2003) is still under vote and being expected to become valid End of 2006. It concerns following changes: • The fridge mean temperature for the “storage test” (Table (T able 2) is 4°C with allowed maximum and minimum temperatures o f 8°C and 0°C. (The fridge mean temperature for the energy test (Table 5) remains at 5°C and must operate between between 10°C and 0°C). • Two tests and an interpolation can be carried out for forced-air (frost-free) appliances. (In the current EN ISO 8561, only one test is allowed so that there is no temperature deviation warmer than –15°C during the defrost cycle). • After the first stabilisation and test period, a further test should be carried out which must be within a temp of 0.5°C and the energy should be within 3%. • The temperature below the test platform is measured and should be within 1.5K of the ambient temperature (Clause 8.4). (This is currently not measured, the room ambient must be 25 ± 0.5°C). • The new test voltage will will be 230 V. The current EN 153 specifies specifies 220 V. • The energy consumption is adjusted by an ambient temperature correction factor (Clause 15.2.1).

New EN153 2006.

The test for all appliances involves setting each ea ch compartment(s) to the characteristic temperature as follows: COMPARTMENT CHARACTERISTIC TEMPERATURE Cellar +8 to +14°C Fresh food compartment (Fridge) mean of +5°C Chill -2 to +3°C 1 star No warmer than -6°C 2 star No warmer than -12°C 3 star No warmer than -18°C 4 star (Freezer) No warmer than -18°C Background.

A cellar compartment is useful for storing fruit, vegetables, beer and and wine. The market share for these is very small. A chill compartment is useful for storage of “delicate” “delicate” foodstuffs e.g. fish, meat and and shellfish. Chill compartments are normally only available with frost-free fridge-freezers. The storage time for the various star compartments will be b e indicated on food packaging but typically it is: 1 star 1 week 2 star 1 month 3 star 3 months A 4 star compartment is a true freezer i.e. it can freeze down fresh food from room temperature and will have a freezing capacity – an amount in kg which can be frozen in 24 hours declared on the rating plate. The freezing capacity test is also covered in EN 153. Exempting frost-free appliances cooled by forced air, once the r egion of the characteristic temperature has been found two 24 hour tests will be carried out; one slightly above and the other slightly below the characteristic characteristic temperature. An interpolation will determine the energy consumption at the precise temperature.


Compartments cooled by forced air are normally frost-free and currently undergo only only one test run. This may change with the introduction of the combined combined standard (ISO EN 15502). This defrost cycle has temperature temperature and time restrictions. Frozen food compartments are packed full of “tylose” which represents the thermal characteristics characteristics of lean beef. (The US test standard uses a sawdust mixture and the Australian standard uses nothing – the compartment is empty!) The volume of the compartment is measured, this crucial to the energy label calculation. calculation. For the energy label consumption of the appliance on test is compared with a “standard energy consumption” for an appliance of that type and size or net volume. This net volume is typically 10 – 15% greater than the volume which can be realistically used b y the consumer. Unlike the test for commercial refrigeration (EN 441), neither the current or proposed EN 153 has any door opening aspect. Since the ambient temperature is 25°C, there is an argument that this presents a similar situation to heat ingress ingress that would be experienced with door opening. Comparative tests between door opening and doors shut have been conducted (See BNC11). MTP research[1] suggests that energy consumption measured for energy lab el information reflects ‘real use’, including compensating for a lack of any door openings and the the more typical UK 20°C ambient. However the energy label testing cannot present ingress of humidity – particularly p articularly important for automatic frost-free appliances 1[2]. This does not matter for timed frost-free appliances, they will defrost every 10-24 hours anyway. With the doors shut for the 3 days of the test, automatic or sensor frost-free appliances may not defrost for 75 hours. Yet in normal use, these will easily show defrost peaks twice per day. Door opening.

One possible solution therefore would be to have a door opening condition for (some) frost-free fros t-free appliances during the test for energy. Alternatively, these appliances could loose their favourable “1.2 factor” factor” in the energy index calculation. Fit for purpose. Fridge temperatures are obviously important for food safety and therefore storage temperatures colder than 5°C are to be welcomed. Appliances with longer cycling times may find it difficult to keep a mean mean of 4°C within the boundaries of 0 and 8°C. It is disappointing that the mean for the energy test in either the prEN 153 or ISO 15502 also has not moved to 4 or even 3°C.

Since 1.7.2010 EU forbid sales of household refrigerators class B-G and only allow sales of class A . furthermore the class is split into 4 groups A, A+, A++, A+++. Each extra + means a 20% higher efficiency respective a 20% less energy consumption, consumption, so that A+++ A+++ is 60% more effective as A. MTP research comparing the standard energy test with a 'real use' scenario shows that some fresh food compartments (fridges) do not quickly recover their correct temperatures. Further research is necessary to consider this issue. Energy Labelling EN 441 for commercial refrigeration.

Similar labelling system exists for commercial refrigerators.

10.6.3. Impact of EU Policy and Measures - a Story of Success The efficiency spread indicated in these classes is based on several considerations: 1) The efficiency of models on the EU cold-appliance market tends to be distributed like a slightly skewed

Gaussian function except that there is a long tail on o n the side of the inefficient models while the efficiency of the most efficient model is bounded.


2) The aim of the label is to encourage people to buy more efficient appliances - this means that it is not necessary to set the width of the efficiency classes such that there are an equal number of models in each class, but rather in such a way that it is a compromise between reflecting the real efficiency distribution of the market at the time that the label is introduced and the efficiency distribution one may hope to achieve after so me years. Thirdly, that the highest efficiency class needs to be theoretically attainable even if it is not attained by b y any model at the time the label is introduced. When the cold-appliance energy label was introduced in 1994 there were almost no models in the A efficiency class available on the market; however, a detailed engineering analysis had shown that it was quite possible to manufacture A class models. Since that time several hundred A class models have become beco me available on the EU market, justifying the principle of leaving the top efficiency class almost empty when a new labelling benchmark is set. Meanwhile C-G models vanished completely f rom the market mainly already as market result. An EU Voluntary Commitment for cold appliances is negotiated with industry, wherein the current C class appliances are phased out as per

January 2004 followed by a "fleet" (i.e., weighted according to the sales o f the different models for each manufacturer) average efficiency of new products, reaching the EEI=52 level by 2006. A new scaling is under negotiation in EU to be established soon.

10.7. Noise of cooling system Also the noise of a refrigerator of o f the refrigerator should be tested, for example according to European rule 86/594/EEC and according to test procedure standard EN 28960. Correct made R600a systems have low noise as result of low lo w pressures. If the noise is higher, it contains air or o r other non condensable gases from the beginning or as result of leak in the low pressure pr essure side, with is -0,5 bar underneath the atmosphere. In Europe it is part of the required label.

10.8. Temperature Rise Test The purpose of this test is to check the time for the temperature rise of test packages in food freezers and frozen food compartments (***) under special test conditions. The temperature rise time is the period between the moment when the warmest M package in the food freezer compartment reaches -18 °C to the moment when any of the M-packages (excluding ** sections) first reach a temperature of -9 °C, when the operation of a refrigerating system is interrupted. How to execute this test can be taken from EN ISO standard 15502 (chapter 16 of ISO I SO 7371, 5155, 8187).

10.9. Freezing Test and Ice-Making Test The freezing capacity is the capacity of freezing down food simulated with Tylose test packages in a defined time or quantity under the ambient temperature of the selected climate class. The test conditions and procedures are described in new EN ISO standard 15502 (as well as in not more valid ISO 5155, 8187, chapter 17. Freezing test (only for refrigerators with freezer compartment and freezers).

For refrigerators with temperature areas underneath 0 °C (* or ** compartments) an ice making test instead of a freezing test have to be executed according to ISO standard 15502 (chapter 17 of previously valid ISO 7371). The ice making capacity described the quantity of ice a system is able to produce during 24h. Alternatively it also can describe the time a water filled tray with a defined quantity of water needs to freeze. Ice making test (only for refrigerators).

10.10. Test of Absence of Odour and Taste With this test the absence of odour and taste in an appliance is tested. The test conditions and procedures are described in ISO standard 15502 (chapter 19 of the previously valid standards sta ndards ISO 7371, 5155, 8187).

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator and Freezer Cooling Circuits. 10. Final Tests, R600a Properties Tables

p. 117

10.11. Refrigerator Performance Tests Calorimetric tests . A calorimetric test was already described in the chapter "Condenser" under "Testing the condenser mounted on

a refrigerator". The whole refrigeration circuit can be measured and optimised by the same test configuration.

But before we describe a systematic testing of the system necessary for optimisation of single components including capillary tube we have to optimise first the charging quantity of the refrigerant to be able to execute further tests. This test of determining the optimal refrigerant filling quantity has always been repeated if the volume of the condenser suction tube, condenser or evaporator changes. See for the determination of the refrigerant fillin g quantity chapter 7.5.) All measurements with a calorimeter can be made acc. to DIN 8977 with type "Secondary-liquid-calorimetric procedure A“ as described in details in this standard. In practise the temperatures of the refrigerant at the inlet of the capillary tube or expansion valve are not on the left curve of the InPi-diagram, but slightly lower. For comparison reasons the CECOMAF GT4-001 standard request to recalculate all results to be on the left curve of the Mollier diagram (InP-i-diagram) (InP -i-diagram) to gain following 2 standard conditions for the calorimetric measurements: Measurements 1 2 Evaporator temp. Condenser temp. Superheat Ambient temp.

-25°C 55°C 32°C 32°C

-30°C 40°C 32°C 32°C

The first measurement stage is recommended by CECOMAF GT4-001 as basis for the catalogues' values of LBP compressors (LBP = Low Back Pressure = low evaporating temperature as used for our applications). The second measurement stage has relations to the operation conditions which we find at the stage just before the thermostat cut off to determine the standard energy consumption. Already out of these a.m. temperature measurements on the refrigerator system and the maintaining of the temperature in the cabinet according to the applied class of the standard we can calculate the reached performance. To improve the data set for performance calculation we should also register the high pressure reached on the condenser and, if existing, the temperatures on the oil cooler. So we will have - beside of the maintained temperatures - in the cabinet according to the supplied standard and class following ENTRY DATA set: Entry Data:

Refrigerator duty Evaporator temperature Condenser temperature Suction condition Delivery condition Liquid return temperature High pressure

Unit

kW °C °C °C °C °C bar abs.

For example:

0,2KW -25°C +55°C +52°C +60°C +24 °C

10.12. Refrigerator circuit measurement positions The measurement of the temperatures of cooled or frozen goods, the position of the Tylose packs with thermocouple probes, the quantity of Tylose packs, the temperature of the environment and which performance tests have to be made and how, all these variables are described in all details in the ISO standards (see chapter "STANDARDS" and the relevant ISO standard tests and drawings). We only describe here where to position the temperature thermocouple feelers and the pressure manometers to measure the refrigeration circuit elements on the models to optimise the refrigeration circuit.

CHEST FREEZERS


p. 118

Thermocouple feelers have to be positioned on the evaporator on the inner wall of the chest freezer or freezer's compartment of the refrigerator and on the refri gerator's evaporators as follows: - 1 probe near the entry point of the evaporator coil (Top), - 1 probe on half height (in case of horizontal coils) or in the middle of the side wall behind which the half of the length of the evaporator tube is positioned (in case of vertical serpentine tube evaporator) and - 1 probe at the exit of the evaporator (often at the bottom of the evaporator). The 3 probes can be replaced by one probe if the position of the probe represents the mean temperature of the evaporator according to different measurements. Evaporator Temperature.

Condenser Temperature. Thermocouples' probes have to be positioned on the tube t ube coils of the condenser. - 1 at the entry point of the condenser - 1 at the middle of the length of the coil and - 1 at the exist point of the condenser. After several trials the 3 measurement points can be replaced by 1 measurement point if the point represents the mean temperature of the condenser.

A small tube inside the foam beside the suction tube from the compressor compartment's side has to be made to place a thermocouple probe on the suction tube.

Suction Condition.

Delivery Condition.

A thermocouple has to be positioned on the delivery tube of the compressor.

A thermocouple can be positioned at the inlet of a capillary tube, if accessible, to measure the liquid return temperature. Often chest freezers have the capillary tube inside the foam. In this case the same hole as the one for the suction condition can be used to position the thermocouple probe.

Liquid Return.

High Pressure. On the tube between compressor and condenser a small hole can be pierced with a special piercing tool and connector valve without without soldering. For example: Refco tube piercing valve HP-41, or Refco Tupper valve E2 36-1 or Refco supper rap LT-36 (5mm, 3/16"), LT-46 (6mm, 1/4" ), LT-56 (8mm, 5/16"), LT-66 (10mm; 3/8); with soldering also the cheap connectors Refco A-31905, A-31906, A-31908, A-31910 A-31910 can be used. A valve pressure gauge has to be connected to this valve. In case of the chest freezer also a hole can be pierced in the filter-dryer and a connector tube can be soldered to this hole.

A vacuum gauge on the compressor filling tube will be connected to measure the low pressure side with a vacuum gauge. The connection between tube and gauge can be a Hansen coupler to be able to fill the system again when needed.

Low Pressure.

10.13. Test Panels It is not possible to describe for all variations of designing and development a systematic test panel. Therefore we will only mention proceedings normally used. To optimise a given system we have to vary components which seem not yet optimal selected and to measure the a.m. data and then to calculate their performance results out of these data. The test panel should be selected in the way that we start to vary components from which we believe that it weakens the most our system balance. How to test, measure and optimise each component used in the refrigerator was already described in the previous chapters. After optimising each component we vary the next one and so on. Many components can be dimensions already according to experience and calculation as described in the previous chapters. But the final diameter and length of the capillary tube under the selected standard and classes to be fulfilled and the optimal charge with refrigerant can only be gained by systematic tests. Between the limits of pre-tests performance tests can be performed to optimise the single refrigerator model. Test panels and test proceedings cannot be designed for all variations of models, but only for each single refrigerator model design and its problem. We can supply our clients with computerised measurement hard- and software to measure systematically the relevant data and to evaluate the data under the reached performances of the refrigeration system.


p. 119

10.14. Refrigeration Performance Calculation and Evaluations There exist different refrigerator system calculation programmes on the market which allow calculating out of the a.m. entry data the important performance results of a refrigerator, r efrigerator, depending on which refrigerant were used. Results

COP - coefficient of refrigerator performance Vol. Flow (suction): Mass flow: High pressure: Low pressure: Pressure ratio: Pressure difference:

m /h kg/sec bar abs. bar abs. bar abs.

Such programs can also be received through the suppliers of refrigerants. For our customers we add a programme which can be used to calculate out of the a.m. measured entry data the reached performance of the refrigerator under good conditions, like Specific Enthalpies:

-

Unit

End of Evaporation Compressor suction Compressor Delivery Expansion valve/Capillary

kJ/kg kJ/kg kJ/kg kJ/kg

Delta Hs

-

Unit

Refrigeration Effect Superheat Compressor Work Total Heat Rejected Sub cooling

kJ/kg kJ/kg kJ/kg kJ/kg kJ/kg

Such performance calculation bases on measurements and following refrigerant properties and formulas: FOR EXAMPLE FOR HFC 134a following calculations and tables are used. The US-National Institute of Standards and Technology (NIST) have issued such a program with a database “ Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)” which allows the calculation of thermodynamic properties under ideal conditions of different refrigerants. It can be purchased online for US$ 200 at http://www.nist.gov/srd/nist23.htm and the Manual can be seen at http://www.nist.gov/srd/webguide/nist23-7/23v7.htm#2.%20INSTALLATION . The comparison of measured data with these calculated optimal data allow the systematic improvement of the circuit by intervening in the areas with higher deviations. 10.14.1. PROPERTY R134a, R600a and R290 PROPERTY

Molecular Weight Boiling Point (1 atm ) Melting Point Critical Temperature Critical Pressure Critical Density Vapour Pressure (25°C) Latent Heat of Vaporisation at nBpt Saturated Vapour Density at nBpt Trouton's Constant Coeff. Vol. Therm. Exp. (LIO, 20°C) Speed of Sound (sat. LIQ)(25°C) Adiabatic Exponent (VAP)(25°C/2.9bar) Acentric Factor Dielectric Constant (VAP)(25°C/1 atm) Dielectric Strength (R12=1) Specific Resistivity (LIO) AC

UNITS

°C °C °C bara kg/I bara kJ/kg kg/m3 kJ/kg.K K-1 m/s

MOhm. cm

R134a

R600a

102.03 -26.22 -101 101 .0 40.55 0.50915 6.63 217 5.231 0.8783 0.003003 (20°C) 702 1.142 0.3256 1 .014 0.5 180

58.124 44.096 -11.7 -42,04 -159.6 135.1 96,67 36.5 0.221 3.5 362 405 2.81 2.6 1.86 1.70 1.95*10-3 (0°C) 810 814

R290


Specific Resistivity (LIQ) DC Purity Solubility In Water (20°C/latm)

MOhm. cm % wt % wt

66000 99.98 0.0773

p. 120

>/= 99,5 0,0054

10.14.2. EQUITY OF STATE (MARTIN-HOU)

∑ Aj + BjTr + Cj exp (-KTr)

Pr = XTr + Vr-B

i=1,4

(Vr-B)

For R134a: X = 3.82825 B = 0.2124913803 K = 7.250023581 Tc, Pc, Vc = 374.15(K) Pc = 40.55(bara) Vc = 1.964058842(I/kg)

A1 = -10.72969406 B1 = 5.0713498381

where Tr = T/Tc , Pr = P/Pc , Vr = V/Vc = V x RHOc

i+1

C1 = -467.15522467 A2 = 14.034313767 B2 = -8.6811368103 C2 = -679.27189635 A3 = -11.321632367 B3 = 8.0404407351 C3 = 1661.953119 A4 = 3.201606791 B4 = -2.3711553933 C4 = -620.50640774

For R600a:

10.14.3. EXTENDED ANTOINE EQUATION B Ln(P) = A + ----- + DT + ELn(T) where P = vapour pressure pressure bara, T = temperature K C+T

For R134a: A = 123.5423 B = -5763.49

D = 0.0304565

For R600a:

C=0 E = -19.55224

10.14.4. LATENT HEAT OF VAPORISATION 4 DHvap = A + Bx + Cx² + Dx³ + Ex where x = (1- (T/Tc)) (1/3) ,

T = Temperature Temperatur e K , Tc = Critical Temperature K, DHvap kJ/kg

For R134a: A =0 B = 225.00842

C = 194.56068 D = -142.9851 E = 57.587846

For R600a:

10.14.5. IDEAL GAS HEAT CAPACITY Cp(ideal) = A + BT + CT² + DT³ + E/T² C =-2.866246E-06 For R134a: D = 1.7812019E-09 A = 0.143897 E=0 B = 0.003005

where T = Temperature K ,

Cp(ideal) kJ/kg.K

For R600a:

10.14.6. SATURATED LIQUID ENTHALPY 4 Hliq = A+Bx+Cx²+Dx³+Ex where x = (1- (T/Tc)) (1/3)

, T = Temperature K , Tc = Critical temperature K , Hliq kJ/kg

For R134a: A = 289.6766 B = -120.9303

C = 58.162283 D = -610.8266 E = 166.65826

10.14.7. LIQUID DENSITY 4 dliq = A + Bx + Cx² + Dx² + Ex For R134a: A = 509.14972 B = 902.40197

For R600a:

where x = (1- (T/Tc)) (1/3) , T = Temperature Temperatur e K, Tc = Critical temperature K, dliq kg/m³ kg/m³

C = 637.09745 D = -504.3096 E = 415.766

10.14.8. LIQUID VISCOSITY Ln µliq = A + B/T + C/T² + D/T³

For R600a:

where

T = Temperature K ,

µ liq

cP


C =-275736 D=0

For R134a: A =-8.52527 B = 2984.6992

For R600a:

10.14.9. LIQUID THERMAL CONDUCTIVITY Kliq = A+Bx+Cx²+Dx³ where x = (1- (T/Tc)) (1/3)

, T = Temperature K , Tc = Critical temperature K , Kliq W/m. K

For R134a: A = 0.078573 B = -0.146406

For R600a:

C = 0.265347 D=0

10.14.10. SURFACE TENSION δ= A(1-T/Tc)1.26 where T = Temperature Temperature K , Tc = Critical temperature K , δ mN/m For R134a: For R600a: A = 60.4 10.14.11. SATURATED VAPOUR DENSITY 4 dvap = A + Bx + Cx² + Dx³ + Ex where x = (1- (T/Tc)) (1/3)

,T = Temperature K , Tc = Critical temperature temperature K , dvap kg/m³

For R134a: -50° to 0°C 0° to +80°C A = 455.45416 A = -403.0344 B = -493.8403 B = 5002.9036 C = -1740 C = -14972.63 D = 2957.1827 D = 17151.088 E = -1108.366 E = -6831.522

For R600a:

10.14.12. VAPOUR VISCOSITY (SAT. VAPOUR) µvap = A + BT + CT² + DT³ where T = Temperature K, For R134a: For R600a: C =-2.21507E-06 A = -.049881 1323 D = 2.82253899E-09 B = 6.239809E-04

µ vap cP

10.14.13. VAPOUR THERMAL CONDUCTIVITY(SAT.VAPOUR) K gas = A + BT + CT² + DT³ where T = Temperature K, Kgas W/m.K For R134a: C = -1 .604876E-07 A = -.012605 D = 3.0361 55E-10 B = 1 .09279E-04 10.14.14. VAPOUR SPEED OF SOUND (SAT. VAPOUR) µ = A + BT + CT² + DT³+ E/T where T = Temperature C = 0.037823 For R134a: For R600a: D = -3.9099E-05 A = 2619.19 E =-171017.1 B = -14.14725

K,

µ m/s

10.15. Tables 10.15.1 R134a LIQUID AND SATURATED VAPOUR ENTHALPY AND LATENT HEAT TEMP °C

-50.0 -40.0 -30.0 -20.0 -10.0 0.0 10.0

LIQUID LATENT ENTH HEAT -----------kJ/kg----------- 

35.26 47.85 60.60 73.53 86.65 100.00 113.59

232.00 225.83 219.39 212.66 205.59 198.13 190.23

SAT VAP LIQUID ENTH cP -----kJ/kg K--- 

267.26 273.67 279.98 286.18 292.24 298.13 303.82

1.2507 1.2666 1.2838 1.3026 1.3233 1.3463 1.3723

ID.GAS cP

0.6916 0.7113 0.7308 0.7499 0.7687 0.7872 0.8055

p. 121


20.0 25.0 30.0 40.0 50.0 60.0 70.0 80.0

127.46 134.51 141.65 156.23 171.28 186.93 203.42 221.20

181.79 177.33 172.70 162.80 151.88 139.58 125.30 107.88

309.25 311.84 314.35 319.03 323.16 326.51 328.72 329.08

1.4022 1.4189 1.4372 1.4794 1.5323 1.6023 1.7028 1.8694

p. 122

0.8234 0.8323 0.8411 0.8586 0.8758 0.8928 0.9096 0.9262

10.15.2 R134a LIQUID DENSITY AND VISCOSITY AND SURF TENSION TABLE: TEMP °C

VAPOUR PRESS Bara

LIQUID DENSITY kg/m³

LIQUID VISCOSITY cP

LIQ.THERM COND W/m.K

SURF TENSION mN/m

-50.0 -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 25.0 30.0 40.0 50.0 60.0 70.0 80.0

0.294 0.512 0.844 1.328 2.005 2.924 4.136 5.697 6.628 7.669 10.118 13.116 16.742 21.081 26.229

1444 1416 1388 1358 1327 1295 1261 1226 1207 1188 1147 1103 1053 997 929

0.50 0.45 0.40 0.35 0.31 0.27 0.24 0.21 0.20 0.19 0.16 0.15 0.13 0.11 0.10

0.115 0.111 0.107 0.103 0.099 0.095 0.091 0.086 0.084 0.082 0.078 0.074 0.069 0.065 0.061

19.3 17.7 16.1 14.6 13.1 11.6 10.2 8.78 8.11 7.44 6.14 4.90 3.72 2.62 1.60

10.15.3 R134a SATURATED VAPOUR DENSITY AND VISCOSITY, THERMAL CONDUCTIVITY AND SPEED OF SOUND TABLE: TEMP °C

SAT.VAPOUR SAT.VAPOUR SAT.VAPOUR SPEED DENSITY VISCOSITY THERM.COND OF SOUND kg/m³ cP W/m.K m/s

-50.0 -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 25.0 30.0 40.0 50.0 60.0 70.0 80.0

1.650 2.772 4.431 6.791 10.05 14.42 20.19 27.70 32.24 37.38 49.80 65.78 86.62 114.45 153.46

0.0104 0.0110 0.0115 0.0119 0.0124 0.0128 0.0133 0.0138 0.0141 0.0143 0.0150 0.0157 0.0165 0.0175 0.0185

0.0072 0.0080 0.0088 0.0097 0.0106 0.0115 0.0124 0.0133 0.0138 0.0142 0.0152 0.0162 0.0172 0.0183 0.0193

140.9 143.2 144.9 146.1 146.7 146.7 146.2 145.0 144.1 143.1 140.3 136.6 131.8 125.7 118.2

Further details for R134a can be take from Transfair T ransfair Calculation Performance Programme, from NIST REFPROP Version 4 of IIR thermodynamic basis, from different programmes of the r efrigerant supplier and their tables. For R134a a wide range of offers of such data programmes and tables exist already on the t he market while such data for R600a and mixtures are not as available as for R134a. Therefore we publish it inside this booklet: boo klet:


p. 123

10.15.4. SATURATED VAPOUR PRESSURE OF R600a and R290 Saturated Vapour Vapour Pressure of R600a t °C -40 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -I8 -17 -I6 -I5 -14 -I3 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 I8 19 20

p kPa 28,8 30.3 30.3 31,8 33,5 33,5 35,2 35,2 36,9 36,9 38,7 38,7 40,6 40,6 42.6 44,6 46,8 49.0 51.2 53,6 56,l 58,6 61,2 63,9 66.8 69.7 72,7 75,8 79,0 82,3 85,7 89,3 92,9 96 7 100,6 104.6 108,7 112,9 117,3 121,8 126,4 131,2 136,1 I41,2 I41,2 146,4 151,7 157,2 162,8 l68,6 174,6 I80,7 187,0 193,4 200,0 206,8 213,7 220,9 228,2 235,7 243,3 251,2 259,2 267,5 275,9 284,6 293,4 302,5

v' 1/kg 1,60 1,60 1,61 l,61 1,61 1,62 1.62 I,62 1,62 I.63 1,63 1,63 I.63 1,64 1,64 1,64 1,65 1,65 1,65 1,66 1.66 I,66 1,66 1,67 I,67 1,67 1,68 I,68 I,68 l,68 l,68 1,69 1,69 1,69 1,70 1.70 1,70 1,71 1,71 1,71 1,72 1,72 1,72 1,73 1,73 1,73 1,74 1,74 1,74 1,75 1,75 1,75 1,76 1,76 1,76 1,77 1,77 1,78 1,78 1,78 1,79 1,79 1,80

v" h' l/kg kJ/kg 1142,9 112,4 1090,4 1090,4 114,5 114,5 1040,8 116,6 994,0 118,8 118,8 949,7 949,7 120,9 120,9 907,7 907,7 123,0 868.0 868.0 125,2 830,4 830,4 127,3 127,3 794,5 129,4 761,0 131,6 729,0 133,7 698,6 135,9 669,7 138,0 642,3 140,2 6l6,2 142,3 591,5 144,5 567,9 146,7 545,5 148,8 524,1 I51,0 503,8 153,2 484,4 155,4 465,9 157,6 448,3 159,8 431,5 162,0 415,5 I64,2 400,2 166,4 385,5 168,6 371,6 371,6 170,8 358,2 358,2 173,0 173,0 345,5 345,5 175,2 333,2 333,2 177,5 321,6 321,6 179,7 179,7 310,4 310,4 181,9 181,9 299,7 299,7 184,2 184,2 289,4 289,4 186,4 186,4 279,6 188,7 270,1 190,9 261,1 193,2 252,4 195,4 244,1 197,7 236,1 200,0 228,5 202,3 221,1 204,6 214,0 206,9 207,2 209,2 200,7 211,5 194,4 194,4 213,8 188,4 216,1 182,5 182,5 218,4 176,9 220,8 171,6 171,6 223,1 166,4 225,4 161,4 227,8 156,6 230,1 151,9 232,5 147,4 234,9 143,1 237,2 139,0 239,6 135,0 135,0 242,0 131,1 131,1 244,4 127,3 246,8

h" kJ/kg 502,9 504,2 504,2 505,4 506,7 506,7 508,0 508,0 509,3 510,6 511,6 511,6 513,2 514,5 515,8 517,1 518,1 519,7 521,0 522,3 523,6 525,0 526,3 526,3 527,6 528,9 530,3 531,6 532,9 534,3 534,3 535,6 537,0 538,3 538,3 539,7 541,0 542,4 543,7 543,7 545,1 545,1 546,4 546,4 547,8 547,8 549,2 550,5 551,9 553,3 554,6 556,0 557,4 558,7 560,1 561,5 562,9 564,2 565,6 567,0 568,4 569,8 571,1 572,5 573,9 575,3 576,7 578,0 579,4 580,5 582,2 553,6 55 3,6

r kJ/kg 390,5 389,6 389,6 388,8 387,9 387,9 387,1 386,3 386,3 385,4 385,4 384,6 383,7 382.9 382,0 381,2 380,3 379,5 378,7 377,8 377,0 376,1 375,3 375,3 374,4 373,6 372,7 371,8 371,0 370,1 369,3 368,4 367,5 367,5 366,7 365,8 365,8 364,9 364,9 364,0 363,2 362,3 361,4 360,5 359,6 358,7 357,8 356,9 356,0 355,1 354,2 353,2 352,3 351,4 350,5 350,5 349,5 348,6 348,6 347,6 346,7 346,7 345,7 344,7 343,8 342,8 341,8 340,8 339,8 338,8 338,8 337,8 337,8 336,8

s' s" kJ/kgK kJ/kg 0,655 2,329 0,664 0,664 2,328 2,328 0,673 2,326 0,682 2,324 0,691 2,323 0,700 2,321 0,708 2,320 0,717 2,319 0,726 2,317 0,735 2,316 0,744 2,315 0,753 2,314 0,762 2,313 0,770 2,312 0,779 2,311 0,788 2,310 0,796 2,309 0,805 2,309 0,814 2,308 0,822 2,307 0,831 2,307 0,840 2,306 0,848 2,306 0,857 2,305 0,865 2,305 0,874 2,304 0,882 2,304 0,891 2,304 0,899 2,303 0,908 2,303 0,916 2,303 0,925 2,303 0,933 2,303 0,942 2,303 0,950 2,303 0,958 2,303 0,967 2,303 0,975 2,303 0,983 2,303 0,992 2,303 1,000 2,303 1,008 2,304 1,017 2,304 1,025 2,304 1,033 2,304 1,041 2,305 1,050 2,305 1,058 2,306 1,066 2,306 1,074 2,306 1,083 2,307 1,091 2,307 1,099 2,308 1,107 2,309 1,115 2,309 1,124 2,310 1,132 2,310 1,140 2,311 1,148 2,312 1,156 2,312 1,164 2,313

T °C 21 22 22 23 24 25 26 27 28 29 30 31 32 33 34 35 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

p kPa 311,7 321,2 321,2 330,9 340,8 351,0 361,3 371,9 382,7 393,8 405,1 416,6 428,4 440,4 452,7 465,2 478,l 491,1 504,5 504,5 531,9 546,0 560,4 575,1 590,1 605,4 620,9 636,8 652,9 669,4 686,1 703,2 720,6 738,3 756,4 774,7 793,4 812,4 83l,S 851,5 871,5 891,8 912,5 933,6 955,0 976,8 999,0 1021,5 l044,4 l044,4 1067,7 1091,3 1115,4 1139,8 1164,6 1189,9 1215,5 1241,5 1267,9 1294,8 1322,1 1349,7

v' 1/kg 1,80 1,80 1,80 l,8l 1,81 1,82 1,52 1,82 1,83 1.83 1,84 l,84 1,85 1,85 1,85 1,86 1,86 1,87 1,87 1,88 I,88 1,89 1,89 1,90 1,90 1,91 1,91 1,92 1,92 1,93 1,93 1,94 1,94 1,95 1,95 1,96 1,97 1,97 1,97 1,98 1,98 1,99 2,00 2,00 2,01 2,01 2,02 2,03 2,03 2,04 2,05 2,05 2,06 2,07 2,07 2,08 2,09 2,10 2,10 2,11 2,12 2,13

v" h' l/kg kJ/kg 123,7 249,2 120,2 120,2 25l,6 25l,6 116,9 254,1 113,6 256,5 1l0,5 258,9 107,4 261,4 104,5 263,8 101,6 266,3 98,9 268,8 96,2 271,2 93,7 273,7 91,2 276,2 88,7 278,7 86,4 281,2 84,1 283,7 81,9 286,3 79,5 288,8 77,8 291,3 75,5 293,9 73,8 296,4 71,9 299,0 70,1 301,6 68,4 304,2 66,6 306,8 65,0 309,4 63,4 312,0 61,8 314,6 60,3 317,2 58,8 319,9 57,3 322,5 55,9 325,2 54,6 327,9 53,3 330,6 52,0 333,3 50,7 336,0 49,5 338,7 48,3 341,4 47,2 344,2 46,l 346,9 45,0 349,7 43,9 352,4 42,9 355,2 4l,9 358,0 40,9 360,8 40,0 363,7 39,0 366,5 38,1 369,3 37,2 372,2 36,4 375,1 35,5 378,0 34,7 380,9 33,9 383,8 33,2 386,7 32,4 389,7 31,7 392,6 30,9 395,6 30,2 398,6 29,5 401,6 28,9 404,6 28,2 407,7

h" kJ/kg 585,0 586,3 586,3 587,7 589,1 589,1 590,5 590,5 591,9 591,9 593,2 593,2 594,6 594,6 596,0 597,4 598,7 600,1 601,5 602,9 604,2 605,6 607,0 608,3 609,7 6ll,l 612,4 6l3.8 615,1 6I6,5 617,8 619,2 620,5 621,9 621,9 623,2 623,2 624,5 624,5 625,9 625,9 627,2 627,2 628,5 628,5 629,8 629,8 631,1 631,1 632,5 633,8 635,1 636,4 637,7 638,9 640,2 641,5 642,8 644,0 645,3 646,6 646,6 647,8 649,0 649,0 650,3 651,5 651,5 652,7 653,9 655,1 656,3 657,5 658,7 659,9 661,0 661,0 662,2 662,2

r s' s" kJ/kg kJ/kgK kJ/kgK 335,7 1,173 2,314 334,7 334,7 1,181 1,181 2,315 2,315 333,7 1,189 2,315 332,6 332,6 1,197 2,316 331,5 331,5 1,205 2,317 330,5 330,5 1,213 2,318 329,4 329,4 1,221 2,319 328,3 328,3 1,229 2,320 327,2 1,238 2.321 326,1 1,246 2,321 325,0 1,254 2,322 323,9 1,262 2,323 322,8 1,270 2,324 321,6 1,278 2,325 320,5 1,286 2,326 319,3 1,294 2,327 318,2 1,302 2,328 317,0 1,310 2,329 315,5 1,319 2,330 3l4,6 1,327 2,331 313,4 1,335 2,332 312,2 1,343 2,333 310,9 1,35l 2,334 309,7 309,7 1,359 2,339 308,4 1,367 2,337 307,2 1,375 2,338 305,9 1,383 2,339 304,6 304,6 1,391 2,340 303,3 303,3 1,400 2,341 302,0 302,0 1,408 2,342 300,6 300,6 1,416 2,343 299,3 299,3 1,424 2,344 297,9 297,9 1,432 2,346 296,6 296,6 1,440 2,347 295,2 295,2 1,448 2,348 293,8 1,456 2,349 292,4 1,465 2,350 290,9 1,473 2,351 289,5 1,481 2,352 288,0 1,489 2,354 286,5 1,497 2,355 285,0 I,505 2,356 283,5 l,5l4 2,357 281,9 1,522 2,359 280,4 1,530 2,359 278,8 1,538 2,360 277,2 277,2 1,547 2,362 275,6 l,555 2,363 274,0 274,0 1,563 2,364 272,3 1,571 2,365 270,6 270,6 1,580 2,366 268,9 1,588 2,367 267,2 1,596 2,368 265,5 1,605 2,369 263,7 1,613 2,370 261,9 1,621 2,371 260,1 1,630 2,372 258,3 l,638 2,373 256,4 256,4 1,646 2,376 254,5 254,5 1,655 2,376


p. 124

Saturated Vapour Pressure of R290 (Propan) t °C -50 -49 -48 -47 -46 -45 -44 -43 -42 -41 -40 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 6 7 8 9 10 11 12 13 14

p kPa 67,3 70,7 74,2 77,9 81,6 85,5 89,6 93,8 93,2 102,7 107.4 112,2 117,2 122,4 127,8 133,3 139,0 144,9 151,0 157,3 163,8 170,5 177,4 184,5 191,8 199,3 207,1 215,1 223,3 231,8 240,5 249,4 258,6 268,0 277,7 287,7 297,9 308,4 319,2 330,3 341,6 153,3 365,2 377,4 389,9 402,8 415,9 429,4 443,2 457,3 471,8 486,6 501,7 517,2 532,9 549,1 565,6 565,6 582,5 599,8 617,5 635,5 653,9 672,7 691,9 711,5

v' 1/kg 1,69 1,70 1,70 1,70 1,71 1.71 1,71 1,72 1,72 1,72 1,73 1,73 1,73 1,74 1,74 1,74 1,75 1,75 1,76 1,76 1,76 1,77 1,77 1,77 1,78 1,78 1,79 1,79 1,79 1,80 1,80 1,81 1,81 1,81 1,82 1,82 1,83 1,83 1,84 1,84 1,84 1,85 1,85 1,86 1,86 1,87 1,87 1,88 1,88 1,89 1,89 1,90 1,90 1,91 1,91 1,92 1,92 1,92 1,93 1,93 1,94 1,94 1,95 1,95 1,96 1,96

v" 1/kg 610,4 583,3 557,7 533,5 510,5 488,8 468,2 448,6 430,1 412,5 395,7 379,8 364,7 350,3 336,6 323,6 311,2 299,4 288,1 277,3 267,1 257,2 247,9 238,9 230,4 222,2 214,4 206,9 199,8 192,9 186,3 180,0 174,0 168,2 162,7 157,3 152,2 147,3 142,6 138,0 133,7 129,5 125,5 121,6 117,8 114,2 110,8 107,4 104,2 101,1 98,1 95,3 92,5 89,8 87,2 84,7 82,3 82,3 80,0 77,7 75,5 73,4 71,4 69,4 67,5 65,7

h' kJ/kg 75,5 77,8 80,2 82,7 85,1 87,5 89,9 92,3 94.7 '27.1 99,5 102,0 104,4 106,8 109.2 111,7 114,1 116,6 119,0 121,4 123,9 126,4 128,8 171,3 133,8 136,2 138,7 141,2 143,7 146,2 148,7 151,2 153,7 156,2 158,7 161,3 163,8 166,3 168,9 171,4 174,0 176,6 179,1 181,7 184,3 186,9 189,5 192,1 194,7 197,4 200,0 202,6 205,3 207,9 210,6 213,3 216,0 216,0 218,7 221,4 224,1 226,8 229,5 232,3 235,0 237,8

h" kJ/kg 524,9 526,0 527,2 528,4 529,6 530,7 531,9 533,1 534,3 535,5 536,7 537,8 539,0 540,2 541,4 542,6 543,8 545,0 546,1 547,3 548,5 549,7 550,9 552,1 553,3 554,5 555,6 556,8 558,0 559,2 560,4 561,6 562,8 563,9 565,1 566,3 567,5 568,6 569,8 571,0 572,2 573,3 574,5 575,7 576,8 578,0 579,1 580,3 581,4 582,6 583,7 584,9 586,0 587,1 588,3 589,4 590,5 590,5 591,6 592,8 593,9 595,0 596,1 597,2 598,3 599,3

r kJ/kg 449,4 448,2 447,0 445,7 444,5 443,3 442,1 440,8 439,6 438,4 437,1 435,9 434,6 433,4 432,2 430,9 429,7 428,4 427,1 425,9 424,6 423,3 422,1 420,8 419,5 418,2 416,9 415,6 414,3 413,0 411,7 410,4 409,1 407,7 406,4 405,0 403,7 402,3 400,9 399,5 398,2 396,8 395,4 393,9 392,5 391,1 389,6 388,2 386,7 385,2 383,7 382,2 380,7 379,2 377,7 376,1 374,6 374,6 373,0 371,4 369,8 368,2 366,5 364,9 363,2 361,6

s' s" T p v' v" h' h" r s' s" kJ/kgK kJ/kgK °C kPa 1/kg 1/kg kJ/kg kJ/kg kJ/kg kJ/kgK kJ/kgK 0,500 2,514 15 731,5 1,97 63,9 240,6 600,4 359,9 1,143 2,392 0,511 2,511 16 752,0 1,98 62,2 243,3 601,5 358,2 1,152 2,391 0,522 2,507 17 772,8 1,98 60,5 246,1 602,6 356,4 1,162 2,390 0,532 2,503 18 794,0 1,99 58,9 248,9 603,6 354,7 1,171 2,389 0,543 2,500 19 815,7 1,99 57,3 251,8 604,7 352,9 1,181 2,389 0,553 2,496 20 837,8 2,00 55,8 254,6 605,7 351,2 1,190 2,388 0,564 2,493 21 860,4 2,00 54,3 257,4 606,8 349,4 1,200 2,387 0,574 2,490 97 883,4 2,01 52,9 260,3 607,8 347,5 1,209 2,387 0,585 2,487 23 906,8 2,02 51,5 263,1 608,8 345,7 1,219 2,386 0,595 2,483 24 930,7 2,02 50,2 266,0 609,9 343,9 1,228 2,385 0,606 2,480 25 955,1 2,03 48,9 268,9 610,9 342,0 1,238 2,385 0,616 2,477 26 979,9 2,04 47,6 271,8 611,9 340,1 1,247 2,384 0,626 2,475 27 1005 2,04 46,4 274,7 612,9 338,2 1,257 2,383 0,636 2,472 28 1031 2,05 45,2 277,6 613,9 336,2 1,266 2,383 0,647 0,647 29 1057 2,06 44,0 280,6 614,8 334,3 1,276 2,382 0,657 2,466 30 1084 2,06 42,9 283,5 615,8 332,3 1,285 2,381 0,667 2,464 31 1111 2,07 41,8 286,5 616,8 330,3 1,295 2,381 0,677 2,461 32 1139 2,08 40,8 289,5 617,7 328,3 1,305 2,380 0,687 2,459 33 1167 2,09 39,7 292,5 618,7 326,2 1,314 2,380 0,697 2,456 34 1196 2,09 38,7 295,5 619,6 324,1 1,324 2,379 0,707 2,454 35 1225 2,10 37,8 298,5 620,5 322,0 1,333 2,378 0,717 2,451 36 1255 2,11 36,8 301,6 621,4 319,9 1,343 2,378 0,727 2,449 37 1285 2,12 35,9 304,6 622,3 317,7 1,353 2,377 0,737 2,447 38 1316 2,12 35,0 307,7 623,2 315,5 1,362 2,376 0,747 2,445 39 1347 2,13 34,1 310,8 624,1 313,3 1,372 2,376 0,757 2,443 40 1379 2,14 33,3 313,9 625,0 311,1 1,382 2,375 0,767 2,441 41 1411 2,15 32,5 317,0 625,8 308,8 1,391 2,374 0,777 2,439 42 1444 2,16 31,7 320,2 626,7 306,5 1,401 2,374 0,787 2,437 43 1478 2,17 30,9 323,3 627,5 304,2 1,411 2,373 0,797 2,435 44 1512 2,17 30,1 326,5 628,3 301,8 1,421 2,372 0,807 2,433 45 1546 2,18 29,4 329,7 629,1 299,4 1,431 2,372 0,817 2,431 46 1581 2,19 28,7 333,0 629,9 296,9 1,440 2,371 0,826 2,430 47 1617 2,20 28,0 336,2 630,7 294,5 1,450 2,370 0,836 2,428 48 1654 2,21 27,3 339,5 631,4 292,0 1,460 2,369 0,846 2,426 49 1690 2,22 26,6 342,8 632,2 289,4 1,470 2,369 0,856 2,425 50 1728 2,23 26,0 346,1 632,9 286,8 1,480 2,368 0,865 2,423 51 1766 2,24 25,3 349,4 633,6 284,2 1,490 2,367 0,875 2,421 52 1805 2,25 24,7 352,8 634,3 281,5 1,500 2,366 0,885 2,420 53 1844 2,26 24,1 356,1 634,9 278,8 1,510 2,365 0,894 2,419 54 1884 2,27 23,5 359,5 635,6 276,0 1,520 2,364 0,904 2,417 55 1925 2,28 22,9 363,0 636,2 273,2 1,531 2,363 0,914 2,416 56 1966 2,29 22,4 366,4 636,8 270,4 1,541 2,362 0,923 2,414 57 2008 2,31 21,8 369,9 637,4 267,5 1,551 2,361 0,933 2,413 58 2050 2,32 21,3 373,4 637,9 264,5 1,561 2,360 0,943 2,412 59 2094 2,33 20,8 377,0 638,5 261,5 1,572 2,359 0,952 2,411 60 2137 2,34 20,3 380,5 639,0 258,4 1,582 2,358 0,962 2,409 61 2182 2,35 19,8 384,2 639,5 255,3 1,592 2,356 0,971 2,408 62 2227 2,37 19,3 387,8 639,9 252,1 1,603 2,355 0,981 2,407 63 2273 2,38 18,8 391,5 640,3 248,9 1,613 2,354 0,990 2,406 64 2319 2,40 18,3 395,2 640,7 245,6 1,624 2,352 1,000 2,405 65 2366 2,41 17,9 398,9 641,1 242,2 1,635 2,351 1,010 2,404 66 2414 2,42 17,4 402,7 641,4 238,7 1,646 2,350 1,019 2,403 67 2463 2,44 17,0 406,5 641,7 235,2 1,656 2,348 1,029 2,402 68 2512 2,45 16,5 410,4 642,0 231,6 1,667 2,346 1,038 2,401 69 2562 2,47 16,1 414,3 642,2 227,9 1,678 2,345 1,048 2,400 70 2612 2,49 15,7 418,2 642,4 224,1 1,690 2,343 1,057 2,399 71 2664 2,51 15,3 422,2 642,5 220,3 1,701 2,341 1,057 2,399 72 2716 2,52 14,9 426,3 642,6 216,3 1,712 2,339 1,067 2,398 73 2769 2,54 14,5 430,4 642,7 212,3 1,723 2,337 1,076 2,397 74 2822 2,56 14,1 434,6 642,7 208,1 1,735 2,334 1,086 2,396 75 2877 2,58 13,8 438,8 642,6 203,8 1,747 2,332 1,095 2,395 76 2932 2,60 13,4 443,1 642,5 199,4 1,759 2,330 1,105 2,395 77 2988 2,63 13,0 447,4 642,3 194,8 1,770 2,327 1,114 2,394 78 3044 2,65 12,7 451,9 642,0 190,2 1,783 2,324 1,124 2,393 79 3102 2,67 12,3 456,4 641,7 185,3 1,795 2,321 1,133 2,392 80 3160 2,70 12,0 461,0 641,3 180,3 1,807 2,318

Transfair Engineering: Designing and Prototyping Prototypin g … Cooling Circuits. 10.15 EMC Tests 10.16 Cooling Circuit Pressure Tests

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10.16. Electromagnetic Compatibility Tests (EMC) EMC Electromagnetic compatibility of household refrigerators become part of CE certification. The new EU Directive 2004/108/EC will repeal Directive 89/336/EEC as from 20 July 2007. Products must be constructed so that they do not cause excessive electromagnetic interference and are not unduly affected by electromagnetic interference. How this new directive will apply to household refrigerators, which tests has really to be executed it still has to be clarified. But the manufacturer do not depend anymore on authorized bodies for product approval like in p ast and can make assessment on its own o wn and concentrate of electro smog, which really can be generated by the appliance, which reduce costs. EN 55014 -1:2001—Electromagnetic compatibility—Requirements for household appliances, electric tools, and similar

apparatus—Part 1: Emission—Product family standard. EN 55014-2:1997—Electromagnetic compatibility—Requirements for household appliances, electric tools, and similar apparatus—Part 2: Immunity—Product family standard. EN 61000 -part 3-2 (2006): Electromagnetic compatibility (EMC). Limits for harmonic current emissions (equipment input current < 16 A per phase) and part 3-3 Voltage fluctuation and flicker limits This process will ultimately lead to affixing of a CE mark on the product prod uct when coupled with all other relevant requirements of applicable new approach directives.

10.17.

Cooling Circuit Pressure Test

Even if Isobutane explode inside the system, which theoretically could happen, according to tests executed by Liebherr and others the maximum pressure peak of 12 bars are created during explosion in the cooling circuit and this pressure should remains under the critical load of any cooling circuit components components and joints. The IEC/EN 600335-2-24 section 22.7 requires a pressure test on circuit components for flammable refrigerants. They should withstand an absolute pressure of 3.5 times of the saturated vapour pressure of the refrigerant at 70 °C for parts exposed to the high side pressure during normal operation, that means 35 bar relative ; 5 times of the saturated vapour pressure of the refrigerant at 20 °C for parts exposed to the low side pressure during normal operation, that means 10 bar relative; The pressures are gauged pressures. Also the European Pressure Equipment Directive (PED) 97/23/EC from 29 November 1999 requires that all items of pressure equipment placed on the market in the European Economic Area (EEA) after May 2002 must comply with this directive. So the complete cooling circuit, even the ones filled without flammable refrigerants, all without pressure relieve valve must be able to withstand the maximum pressure, which can be built up inside the circuit. We should add a 50% reserve before bursting. Such pressure is normally not critical for household refrigerator cooling circuit components and correctly made brazing and other joints, but it deforms Aluminium Roll Bond and other flat copper or aluminium components, like flat accumulators or receivers. A refrigerator manufacturer should insist today on the conformity declaration of components manufacturers (compressor, filter dryers, accumulators, valves, condensers, evaporators and tubes) and have to execute refrigerator type pressure tests for type approval and - to control the type approval conform manufacturing process - at least pressure tests on samples or on all refrigerators, if no deformation will happen, for example during Helium leak test (see Chapter 4.7. in Transfair Engineering: Evacuation, Charging, Leak Detection Detection and Performance Testing in the Household Refrigerator production Today 2006, to stress the joints.

Transfair Engineering: Engineering: Designing and Prototyping … Cooling Circuits. 11. Converting refrigerators refrigerators to 134a and to R600a Systems

11.

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Converting Household Refrigerators from CFC-12 to HFC-134a Systems and from HFC-134a to HC-600a Systems

11.1. Converting Household Refrigerators from CFC-12 to HFC-134a Systems Under the condition that the CFC-12 model was working already quite optimal for the climate class designed for, following fast approach for the conversion from CFC-12 to HFC-134a can be made. If the existing model was not very ver y good it is much better to redesign the complete system according to thi s booklet, than to modify single items ite ms already not good designed. 1.

The R134a –compressor to be selected should have the same capacity according to ASHRAE or CECOMAF standard as the one used for the R12 system; that means that the displacement of the R134a is 8-12% higher. In the last 5 years many energy optimised opti mised models are available, even now for tropical regions which should be preferred selected (see chapter 2.10).

2.

Condenser selection:

3.

Compressor water evaporation tray:

4.

The miscibility of refrigerant of refrigerant and oil differ in R12 and R134a systems. In HFC-134a systems more ester oil is passing the circuit as in the past done by Mineral oil used in CFC-12 systems. The cross cr oss section of channels should be equal, not reduced in bending areas or because of bad quality. Oil pockets in which oil can accumulate should b e avoided. These are typical problems of Roll-Bond evaporators; therefore the Roll-Bond was often replaced by tubes-onsheet evaporators during this conversion. Also unnecessary parallel channels (in bending areas often used) do not help. In In opposite they reduce needed optimal refrigerant speed. Such cross section size must be selected, which allow to reach a refrigerant gas speed of 4-5m/sec. By this optimal speed of 4-5m/sec. in the evaporator the efficiency is b est, the maximum pressure drop is limited, li mited, that means the temperature difference between evaporator inlet and outlet in stable, not in pull down conditions should be kept in the range of 1°K).

5.

HFC-134a systems needs more efficient filter with molecular sleeves of 3Å instead of 4Å, like XH7 or XH-9 from Union Carbide or Siliporite H3R. The quantity should be about 20% bigger or the same as used in past if i f it was good dimensioned, but the cleanliness standard to be kept on purchased components and during operation are much higher (compressor and dryer loaded with dry Nitrogen, condenser and evaporator cleaned with dry air(dew point -45°C) etc. (see chapter 7.3.).

6.

The tests should start with the size and length of capillary tube as recommended by the compressor manufacturer, which is because of higher pressur e difference, lower mass flow and volume flow much longer (0.71mm inner dia. of 3-4 m length), and than optimized in length under following conditions:

Compressor selection:

In the first stage of development often the same condenser (and evaporator) can be used in a HFC134a household refrigerator as used for CFC-12, if the condensing capacity and U-value of the CFC-12 model was not near the technical border in the past. Because of the a.m. higher compressor displacement, the U-value of condenser theoretically should be increased. In praxis freezers and refri gerators with large freezers for subtropical and tropical climate classes, or refrigerator models made for tropical climate classes needs regularly a larger condensing surface. Only in few freezers made for tropical conditions, the super heat is i s so high (see chapter 3.4. oil cooling condensers), that an about 30% bigger condenser with oil and with a gas circuit and other compressor compressor types with 5 tube joints are needed. The condenser can be tested acc. to Chapter 3.6. Especially a refrigerator without freezer or freezer hermetically separated from the refrigerator should drain the condensed water from the evaporator by a tube to cool the compressor shell. A tray on top of the compressor should be installed, which reduces the condensing demand and energy consumption by about 15%. Evaporator selection:

Filter dryer selection:

Capillary tube selection:

- In the first step the capillary capacity can be measured with test apparatus (chapter 4.2.) with HCF-134a at 14,9 bar and 55°C condensing temperature and after sub cooling (see item 7). The pressure drop through the capillary should be according to the evaporating temperature to be reached (see table or use p rogram), the capillary capacity (l/min) near


p. 136

the ideal conditions according to the table or program and the th e calculation in chapter 4.1.) that vapour come out of capillary (temperature difference of liquid and vapour at evaporator inlet), - max. 7 % of evaporator in worse conditions should be liquid filled. (to be measured by identification of temperature zones in the evaporator inlet). - The behaviour is changing not only by changing of capillary tube length, environmental temperatures and loads, but also it depends from refrigerant charge quantity to be optimized, so that all tests must be repeated several times till all parameters are optimal. 7.

Sub cooling of HFC-134a increases the nominal capacity by about 23%, 4% more than in a CFC-12 model. So it is a must for a HFC-134a system. The capillary tube should be winded round the cold suction tube of the compressor covered by a shrink film sleeve.

8.

HFC- Refrigerant charge quantity:

Sub cooling heat exchanger:

The optimal HFC-134a charge quantity is the one which reaches 3-5°C s uperheat above the saturated temperature which matches the measured pressure (see table or use program) between evaporator outlet and compressor inlet. It is about 10% less than the CFC-12 charge quantity (if all condenser, compressor, filter and evaporator would be the same). Fine tuning of charge quantit y is needed (see chapter 7.5.4.). By modifying other circuit parts the test must be repeated.

9. It is always useful to use us e the conversion to optimize the refrigerator in all areas, stating from thermal insulation, elimination of thermal bridges (Chapter 1.5.), using energy optimized opti mized compressors (chapter 2.10), eliminate accumulators by using vertical u-bends in refrigerator evaporator (chapter 5.2.2.), etc. T he conditions for different models and climate classes are varying so much that some single items cannot ca nnot be recommended in this chapter and therefore it is usef ul to go through all chapters and recommended measurements and tests again for the development of an op timal system. 10. The additional requirements on cleanliness in circuit components and during processing , the limited time of opening the compressor and filter dryer, the cleaning of condensers and evaporators, the higher demand on the brazing quality, a ll this can only be reached by strict quality q uality control measures, which must accompany the introduction of R134a model manufacturing (see Chapter 7.3. and Transfair Engineering: Evacuation, Charging, Leak detection and Perfor mance Testing in the Household Refrigerator Industries today, Düsseldorf 2001). Last not least all manufacturers – though they don’t like to admit it – test regularly the models of their best competitors and compare their efficiency values with the ones of their own products to identify own weak areas to be improved. So also such an approach is strongly recommended.

11.2. Converting Household Refrigerators from HFC-134a to HC-600a Systems A fast track approach for the conversion from HFC-134a to HC-600a models as made from CFC-12 to HFC-134a in chapter 11.1. is not possible for the conversion from HFC-134a to HC-600a household refrigerators. The behaviour of the HC-600a refrigerant is so different from the one of HFC-134a that nearly all cooling circuit components must be redesigned. Therefore it does not make sense now to repeat r epeat the booklet. Few relevant aspects should be taken first into consideration before the design conversion to HC-600a models s hould start: 1.

The cabinet, cooling circuit and electrical design :

Most important is the separation of electrics and cooling circuit, specially all their joints, that even in case of a leak no explosion can happen (chapter 8.2.4.); otherwise special protected electrical component must be used, which are often more expensive and sometimes have the chance that their protection will break. Additional tests have to be made on the design (Chapter 8.5.3.-8.5.5) and on each produced refrigerator (Chapter 8.5.2.). And the HC-600a system must be marked for service reasons. Defrost models with foamed in tube-onsheet (=TOP) evaporators behind the liner are safe, efficient and cheap to be made.

2.

Safety precautions during charging of HC -600a

refrigerators and working on the circuit filled with HC-600a must be

made to prevent explosion (see Chapter 7.4.) 3. In some cases the foreseen compressor compartment size must be increased for a HC-600a compressor with 70-80% bigger displacement volume. For example a 160kcal compressor needs about 8cc HFC-134a, but 13 cc HC-600a. The


p. 137

electric coil and energy consumption by different cylinder sizes of HFC-134a and HC-600a are practically the same for the same cooling capacity. 4. The charge tolerances of HC-600a is much smaller, even less than expected from the lower charge quantity. The requirement on fine tuning of charge quantity, the charge accuracy must be inside the range of 1g and the leak detection inside the range of 1 g per year. Too high charge can cause oil film break on the cylinder. 5. If all are optimized HC-600a systems today are at least 5% more efficient as the HFC-134a models, if all other conditions are comparable. In addition in can be stronger improved by a run capacitor as HFC-134a models. 6. Normal mineral oil can be used in the HC-600a compressors and this eliminates a lot of cleanliness problems using HFC134a systems with hydroscopic ester oil (humidity, chlorine, oxidation, grease and mineral oil). But the demand on cleanliness has not been diminished , only changed. Because of much lower refrigerant quantity same absolute impurity has higher thermodynamic effects if it is a gas or can be vaporized. All non-condensable gases – even diluted inside the compressor oil, must be removed by special evacuation processes under compressor run (see Transfair Engineering: Evacuation, Charging, Leak detection and Performance Testing in the Household Refrigerator Industries today, Düsseldorf 2001). Only by high cleanliness the efficiency advantage can be reached. Except the a.m. points the designing of R600a is a standard refrigerator engineering work.

Transfair Engineering: Engineering: Designing and Prototyping of Refrigerator Refrigerator and Freezer Cooling Circuits. 12. IEC and EN Standards

12.

Standards

12.7.

EN Standards for refrigerators

p. 138

The standards, as already mentioned in the booklet and applied, specify which tests according to which methods the household refrigerator manufacturer have to execute for household refrigerator type approval in Europe for example to issue CE conformity declaration, on manufactured manufactured samples or all made made refrigerators to insure that his production is conform with type approval. Following international or relevant national standards exist for refrigerators and freezers:

Household refrigerator -

(2005): Household refrigerating appliances appliances - Characteristics and test methods methods (ISO 15502:2005); it ISO EN 7371 replaced the 4 withdrawn withdrawn standards: - Performance of household refrigerating appliances - refrigerators refrigerators with or without low EN ISO 15502

temperature compartment; compartment; ISO 8187 EN 28187 - Household refrigerating appliances - Refrigerators-freezers' Refrigerators-freezers' characteristics and test methods; ISO EN 5155 - Household refrigerating refrigerating appliances - Frozen food storage cabinet and food freezers characteristics and test methods; ISO EN 8561 Household Frost free refrigerating appliances, refrigerators, refrigerator-freezers refrigerator-freezers characteristics and test methods.

-

Methods of measuring the energy consumption of electric mains operated household refrigerators, frozen food storage cabinets, food freezers and their combinations, t ogether with associated characteristics

EN 153 (2006):

Safety Standards for Refrigerators and F reezers IEC /EN/UL/J/GOST etc. Standard 60335, Part 1: Safety of household and similar electric appliances, and IEC /EN/UL/J/GOST etc. Standard 60335, Part 2-24 (2005): Particular requirements for refrigerator appliances and ice makers. - IEC-EN-UL-J-GOST etc. Standard 60335, Part 2-89 (2007): Particular requirements for commercial refrigerating

-

appliances with an incorporated or remote refrigerant condensing unit or compressor, Vers. 1.2. For flammable refrigerants (R600a) these standards specify t o carry out risk assessment to control flammability risk by tests clauses 22. (1996/2002): Circuit components for refrigerating systems - Part 1: Testing, Part 2: 2 : Sealed systems; Requirements, (2002): Part 3: Closed systems; Requirements

DIN 8964

To be applied on complete cooling circuit EU PED -Pressure Equipment Directive 97/23/EC by pressurization of the circuit by 15bar for R600a and 23 bar for R134a.

Electric Components -

Electrical standards of IEC/EN for each used electrical part and in Europe the EU Low Voltage Directive (73/23/EEC) as amended 93/68/EEC.

-

Fan motor electric safety EN 60335-2-80

and an d

-

Pressure switch EN 60730-2-9

-

Electric terminal box on compressor and in zone with potential po tential R600a leaks must be

EN60335-2-24 Annex AA: locked-rotor test fan motor

Compressor electric safety: EN60335-1 and 2-34 made in accordance with “n” protection (class IP 54 if flammable gas cannot accumulate or higher) according to IEC60079-15 and correspond to the required "Zone 2" regulations. The protection device must be connected according to the wiring diagram. The wires (PTC control circuit) between terminals) and compressor terminal plate must be either shielded or twisted cable (danger of inductance).

EMC Electromagnetic compatibility

-

Directive 2004/108/EC. The new EMC Directive has been published in the Official J ournal of the European Union, L 390/24, 31 December 2004, and will repeal Directive 89/336/EEC as from 20 July 2007. Products must be constructed so that they do not cause excessive electromagnetic interference and are not unduly affected by electromagnetic interference. How this new directive will apply to household refrigerators, which tests has really to be executed it still has to be


-

p. 139

clarified. But the manufacturer do not depend anymore on authorized bodies to approve and can make assessment on its own, which reduce costs. EN 55014 -1:2001—Electromagnetic compatibility—Requirements for household appliances, electric tools, and similar apparatus—Part 1: Emission—Product family standard. EN 55014-2:1997—Electromagnetic compatibility—Requirements for household appliances, electric tools, and similar apparatus—Part 2: Immunity—Product family standard. EN 61000 -part 3-2 (2006): Electromagnetic compatibility (EMC). Limits for harmonic current emissions (equipment input current < 16 A per phase) and part 3-3 Voltage fluctuation and flicker limits

This process will ultimately lead to affixing of a CE mark on the product prod uct when coupled with all other relevant requirements of applicable new approach directives.

Commercial refrigerator -

EN ISO 23953

conditions.

(2006) Refrigerated display cabinets – Part 1 Vocabulary, Part 2: Classification, requirements and test

-

EN 441: Methods of measuring the energy consumption, energy labelling of co mmercial refrigerators.

-

EN378: For design, operation and maintenance of refrigeration plants with flammable refri gerants (Group L3), special

safety regulations apply. Belonging to these regulations, amongst other things, are special protection devices against excessive pressure and special features in design and arrangement of electrical equipment. Mor eover, steps are to be taken that in case of a refrigerant leak, it is harmlessly vented away so that no explosive mixture can occur. The exact design regulations are determined in the Standards, e.g. EN378 / In Germany VBG20 / draft DIN 7003 / DIN VDE 0165 / VDE 0100. With the present regulations, a separate agreement is to be met between the plant contractors and the operator. According to the design and refrigerant charge, individual authorisation fro m the industrial regulatory authority may also be required. Additionally, the designer of such plants must b e certified in dealing with flammable refrigerants; for the operating personnel, qualified instruction is required. The present standards only cover design regulations for stationary plants.

Absorption refrigerator - EN 732 (1998):

Specifications for dedicated liquefied petroleum gas appliances - Absorption refrigerators.

Valves - EN 12284 (2004):

Kälteanlagen und Wärmepumpen - Ventile - Anforderungen, Prüfung und Kennzeichnung

Compressor -

EN 12900 (2005) : Refrigerant compressors - Rating conditions, tolerances and presentation of

data.

EN 13771 -1 (2003 /2005): Compressors and condensing units for

refrigeration - Performance testing and test methods Part 1: Refrigerant compressors. This part 1 of the European Standard applies only to refrigerant refri gerant compressors and describes a number of selected performance test methods. T hese methods provide sufficiently accurate results for the determination of the refrigerating capacity, power absorbed, refrigerant mass flow, ise ntropic efficiency and the coefficient of performance. This standard applies only to performance perfor mance tests conducted at the manufacturer's works or wherever the equipment for testing to the accuracy required is available. The t ype of measuring instrument and the limits within which measurements shall be made are listed in normative nor mative annex A.

Compressor safety

-

manufacturer's performance

Compressor electric safety: EN60335-1 and 2-34 EN 12693 (1997) Kälteanlagen und Wärmepumpen - Sicherheitstechnische und umweltrelevante Anforderungen Kältemittel-Verdichter


p. 140

Condenser -

(2003 /2005): Compressors and condensing units for refrigeration - Performance testing and test methodsPart 2: Condensing units.

-

(2000): Condensing units for refrigeration - Rating conditions, tolerances and presentation of manufacturer's performance data.

-

EN 327 Air cooled refrigerant condensers, Heat exchangers. Forced convection air cooled refrigerant condensers. Test

-

EN 13771-2

EN 13215

procedure for establishing performance.

EN 13136 (2005): Refrigerating

systems and heat pumps - Pressure Pr essure relief devices and their associated piping - Methods

for calculation. -

EN 13313 (2002):

Refrigerating systems and heat pumps - Competence of personnel. This European Standard establishes procedures for achieving and assessing the competence of persons who design, install, test and commission, maintain, repair and dispose of refrigerating systems with respect r espect to health, safety, environmental and energy conservation requirements. This European Standard does not apply to thos e persons who carry out work on the basis of instructions if they are supervised by a competent person.

-

EN 14276 (2002):

Pressure equipment for refrigerating systems and heat pumps - Part 1: Vessels - General requirements;

Filter Dryer -

DIN 8949 (2000):

Refrigerant filter driers – Testing

Acoustical noise -

EN 28960 (1993) Refrigerators, frozen food storage cabinets and food freezers for household and similar use; measurement of emission of airborne acoustical noise (ISO 8960:1991).

EN Standards can be purchased from the following Institutions: Great Britain: British Standards Institution (BSI), (BSI) , Tel: +44 20 8996 9001, Order by Fax: +44 20 8996 7001 (with credit card details), by post: BSI Customer Services c/o Cash Office, PO Box 16206, London W4 4ZL 4 ZL (cash with order) or by internet http://www.bsi-global.com/index.xalter France: Association Française de Normalisation (AFNOR), Serv. "Qualite de la Vie" (SQV), Tour Europe, F-92049 Paris La Défense CEDEX TEL: + 33 142 91 55 33 FAX: + 33 142 91 56 56 Germany: Beuth-Verlag GmbH, Burggrafenstrasse 4-10, D-10787 Berlin; TEL: +49 302601 2260; FAX: +49 30 26011260; http://www.beuth.de/ Italy: Ente Nazionale Italiano di Unificazione (UNI), Via Battistotti Sassi 11/b, I-20133 Milano TEL: +39 270 0241 FAX: +39 270 106 106 Spain: Asociación Espanola de Normalización y Certificación (AENOR), Genova 6, E-28004 Madrid TEL: + 34 14 32 60 00 FAX: + 34 13 10 45 96

EU Directives http://europa.eu.int/comm/enterprise/electr_equipment/legislat.htm http://europa.eu.int/comm/enterprise/newapproach/standardization/harmstds/reflist.html


12.8.

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ISO Standards

ISO Standards are at least in our areas identical with EN and can be received by http://www.iso.org/

12.9.

IEC standards

IEC Standards can be received by http://www.iec.ch/ or by the national standard institutes of member countries or their publishers. In EU from the institutes i nstitutes or publishers as already mentioned in chapter 12.1.

12.10.

Some selected US Standards for refrigerators

Household refrigerator -

-

ANSI/AHAM HRF 1 (2004): Energy, Performance and Capacity of Household Refrigerators, RefrigeratorFreezers and Freezers. The purpose of this standard is to establish a uniform and repeatable procedure or standard method for measuring specified product characteristics of household refrigerators, household wine chillers and household freezers. This standard covers definitions, methods for computing volumes and shelf areas, methods for determining volumes of special features, performance test procedures, durability test procedures, methods for determining energy consumption and energy factor, and safety recommendations. The US-UL signed the above IEC 60335 1 and 2-24. In addition there exists ANSI/ASHRAE Standard 15-2004 – Safety Standard for Refrigeration Systems. ANSI/ASHRAE 15-2004 is the newest version of one of ASHRAE’s oldest standards. This version is a republication re publication of ANSI/ASHRAE 15-2001, including addendum a. The reader is r eferred to that addendum as well as Appendix J of this standard for changes that have been made since the original publication of ANSI/ASHRAE 15-2001. Among those changes were changes to the treatment of flammable r efrigerants, including correction of an omission in the 2001 200 1 standard. In addition, changes were made to the requirements for press ure vessel protection and references were updated. This standard is directed to ward the safety of persons and property on or near the premises where refrigeration facilities are located. It includes specifications for fabrication of tight systems but does not address the effects of refrigerant emissions on o n the environment. For information on the environmental effects of refrigerant emissions, see ASHRAE Guideline 3-1996, Reducing Emission of Halogenated Refrigerants in Refrigeration and Air-Conditioning Equipment and Systems.

Safety Standards for Refrigerators and F reezers - UL 60335, Part 1: Safety Saf ety of household and similar electric appliances, and - UL 60335, Part 2-24 (2005): P articular requirements for refrigerator appliances and ice makers. - UL 250: Standard for Safety Household Refrigerators and Freezers

Commercial refrigerator -

-

Method of Testing Commercial Refrigerators and Freezers. T his revision of Standard 72 combines Standard 72-1998 for open refrigerators and Standard 117-2002 for closed refrigerators. It prescribes a uniform method of testing open and closed commercial refrigerators and freezers for rating so that comparative evaluations can be made of energy consumption, product temperature performance, refrigeration load, the suction pressures required, and other performance factors. T he standard also clarifies door opening requirements, shelf s helf loading, and test definitions, and includes requirements that improve the consistency of ambient temperatures. This standard should be useful to the design engineer respons ible for rating open or closed commercial refrigerators. ANSI-NSF 7-2001: Commercial Refrigerators and Freezers ANSI/ASHRAE Standard 72 (2005):

Electric safety standards: UL 471Standard for Safety Commercial Refrigerators and Freezers, 2006

-

UL 399 Standard for Drinking-Water Coolers UL 541Standard 541Standard for Refrigerated Vending Machines UL 563Standard 563Standard for Ice Makers UL 621Standard 621Standard for Ice Cream Makers


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Compressor -

-

Methods of Testing for Rating Positive Displacement Refrigerant Compressors and Condensing Units. This standard applies to the methods of testing for rating single-stage positive-displacement refrigerant compressors and condensing units that (a) do not have liquid injection and (b) are operated at subcritical (saturated) temperatures of the refrigerant. It also applies to the methods of testing for rating r ating single-stage positive-displacement refrigerant compressors and condensing units that (a) incorpor ate liquid injection that is controlled by a steady flow flo w rate method and (b) are operated at subcritical (saturated) temperatures of the r efrigerant. This standard applies to all of o f the refrigerants listed in the ASHRAE Handbook — Fundamentals and in ANSI/ ASHRAE Standard 342 that fall within the scope defined above. UL 894: Safety of hermetic compressors. ANSI/ASHRAE 23(2005):

Condenser -

Method of Testing for Rating Remote Mechanical-Draft Air-Cooled Refrigerant Condensers. This reaffirmation of ANSI/ASHRAE Standard 20-1997 prescribes methods of laboratory testing to measure the heat rejection capabilities of remote mechanical draft, air-cooled refrigerant condensers for refrigerating and air conditioning. The objective is to ensure uniform performance information for establishing ratings. The T he changes made for the 2006 reaffirmation were that the references r eferences were updated. ANSI/ASHRAE Standard 20-1997 (RA 2006):

Capillary -

Method of Testing Flow Capacity of Refrigerant Capillary Tubes. It provides a uniform procedure for testing capillary tubes by determining the dry nitrogen flow capacity under specific test conditions so the procedures may serve as a primary standard for use by all test laboratories. Provides a basis for agreement between capillary tube manufacturers and users, and provides a standard procedure against which all other methods of tests may be checked. Dual units of measurement. ANSI/ASHRAE 28 (1996) (RA 2006):

Filter dryer -

-

-

-

ANSI/ASHRAE Standard 35 (1992) : Desiccants for Refrigerant Drying, Method of Testing. T esting. This standard is under

continuous maintenance, which is a process ASHRAE uses to keep standards current through the issuance of addenda, or revisions. When they are available, these addenda can be downloaded for free at the following page of the ASHRAE web site: http://www.ashrae.org/template/TechnologyLinkLanding/category/1631 . When they are available, interpretations of the standard, issued by the s ponsoring technical committee, also may be downloaded for free at the following address: http://www.ashrae.org/template/TechnologyLinkLanding/category/1686 . Errata lists are issued occasionally and may be downloaded for free at the following address: http://www.ashrae.org/template/TechnologyLinkLanding/category/1685 ANSI/ASHRAE Standard 63.1 (1995) (RA 2001): Method of Testing Liquid Line Refrigerant Driers. It prescribes test methods for determining flow capacity and water capacity performance characteristics of liquid line refrigerant driers. It applies to driers that employ a desiccant. d esiccant. The water capacity test method prescribed can be used to test a drier either "as received" or after being reactivated in accordance with manufacturer's recommendations. Dual units of measurement. ANSI/ASHRAE Standard 63.2 (1996): Method of Testing Liquid Line Filter-Drier Filtration Capability. It prescribes a laboratory test method for evaluating the filtration capability of filters and filter-driers used in liquid lines of refrigeration systems. ANSI/ASHRAE Standard 78 (1985) (RA 2003): Method of Testing Flow Capacity of Suction Line Filters and FilterDriers. It establishes a method for measuring the flow capacity of refrigerant suction su ction line filters and filter-driers. Intended for use on both sealed model and replaceable element type suction line filters and filter-driers of all types. Dual units of measurement. ARI STANDARD 710:86 Absorption Capacity of dryers

ANSI Standards:

http://webstore.ansi.org/ansidocstore/default.asp


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12.11. Relevant EU Directives for refrigerators EU Energy labelling of household refrigerators

DIRECTIVE 2003/66/EC of 3 July 2003 amending Directive 94/2/EC implementing Council Directive 92/75/EEC with regard to energy labelling of household electric refrigerators, freezers and their combinations . It was already described in chapter

10.6.2.

EU Low Voltage Directive. The Low Voltage Directive (73/23/EEC) as amended 93/68/EEC. The relevant Harmonised Standards listed on the following web-site address

http://europa.eu.int/comm/enterpr http://europa.eu.int/comm/enterprise/newappro ise/newapproach/standardizatio ach/standardization/harmstds/re n/harmstds/reflist.html flist.html

The Electrical Equipment (Safety) Regulations (LVD) (LVD) applies to all electrical equipment designed for use with a voltage rating of between 50 and 1000 V AC and between 75 and 1500 V DC. Broadly the scope of the LVD covers consumer and capital goods designed to operate within those voltage limits, including in particular electrical appliances, lighting equipment including ballasts, switch gear a nd control gear, electric wiring, appliance couplers and cord sets, electrical installation equipment, etc. and electrical equipment intended for incorporation incorporation into other equipment such a s transformers and motors. The Directive covers all risks arising from the use of electrical equipment, including not just electrical ones but also mechanical, chemical (such as, in particular, emission of aggressive substances), health aspects of noise and vibrations, and ergonomic aspects as far as ergonomic ergonomic requirements are necessary to protect against hazards in the sense of the Directive. The LVD lays down eleven “safety objectives”, which represent the essential requirements of this Directive. Products are presumed to conform to the safety objectives of the LVD where the equipment has been manufactured in accordance with a harmonised standard. Alternatively, Alternatively, the manufacturer manufacturer may construct the product in conformity with the essential requirements (safety objectives) of the LVD, without applying harmonised, harmonised, international or national standards. In such a case the product will not benefit from presumption presumption of conformity and therefore the manufacturer must include in the technical documentation a description of the solutions adopted to sati sfy the safety aspects of the Directive. Before a product is placed on the market the following following must happen:

• • •

The manufacturer must put together a technical documentation which makes it possible to assess whether the product complies with the directive The manufacturer or the authorised representative must draw up a ‘declaration of conformity’. conformity’. The manufacturer or the authorised representative must affix the CE marking

LVD Services Offered

• • • • •

Advice on the applicability and completeness of standards to products Testing to harmonised, international, national standards, or client’s own specification. Assessment for compliance with the LVD Assessment of the technical documentation A notified body report in accordance with article 11 of the LVD.

Pressure Equipment Directive (PED) The European Pressure Equipment Directive (PED) 97/23/EC came into force on 29 November 1999. All items of pressure equipment placed on the market in the European Economic Area (EEA) after May 2002 must comply with the Directive and have evidence of compliance by carrying the CE marking as applicable. Why apply the PED?

Legislation across the EEA requires that all applicable items of pressure equipment must be fully compliant with the PED. As a result, manufacturers must revise their working practice and develop the appropriate Technical Files for their full product range. The PED encompasses design verification, material selection, manufacturing/fabrication manufacturing/fabrication practices and qualification, product testing, product marking and user instruction compilation. For those manufacturers who were compliant prior to May 2002, placing the CE marking on their pressure equipment means that equipment has a passport to free trade and must go into service in all Member States of the EEA, without the need to comply with current National Regulations. Regulations. This can result in savings on the cost for statutory inspection as required for Member States such as France, Germany and Italy. How do I comply with the PED?

The PED offers manufacturers of pressure equipment 14 different conformity assessment options which permit the pressure equipment manufacturer to demonstrate compliance by variants on Quality Assurance, Direct Inspection or Surveillance of Testing offered by the Notified Body.


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Companies already ISO 9000 compliant compliant can take advantage of their current quality systems and use this as a foundation to satisfy the Essential Safety Requirements of the PED. In which case compliance can be achieved through QA assessments from their appointed Notified Body only, rather than by third party Notified Body product inspection. If the manufacturer has not been formally accredited to the ISO 9000 series, Notified Body services under the PED QA approaches.

• • • • • • •

Assistance with technical file preparation PED compliant quality system preparation Gap analysis visits. Welding procedure qualification to ASME IX and/or EN ISO 15614 and welder qualification to ASME IX and/or EN 287 Brazing procedure qualification to both ASME IX and EN 13134 and brazer qualification to both ASME IX and EN 13133 Particular Material Appraisal approval to Annex 1 section 4.2b Specially arranged training courses and seminars on compliance tailored specifically to your needs, technical file preparation and compliance quality system preparation.

Product Services:

• • •

A complete compliance service on products including design assessment (modules B/B1), from fire extinguishers to major industrial installations. An expert and dedicated PED team to support you through every step of the certification process. Our understanding of the commercial realities under which you operate mean we help you achieve PED compliance with minimal or no interruption to production, inspections/audits inspections/audits focused on how the required standards can be implemented into today’s engineering practices and consideration to keeping your costs down.

EU ATEX Directives ATEX Manufacturers Directive 94/9/EC.

• • • •

This directive defines each of the following product product groups for use in potentially explosive atmospheres: atmospheres:

Electrical and non-electrical equipment Electrical and non-electrical protective systems Electrical and non-electrical components Electrical and non-electrical safety devices

The directive places responsibilities on the manufacturer manufacturer of these products. The main responsibility of the manufacturer manufacturer is to prevent the formation and ignition of explosive atmospheres. atmospheres. This may be achieved by using one of the well-established protection concepts (such as flameproof flameproof protection, or intrinsic safety), or by proving compliance directly against a set of 'essential health and safety requirements', which are given in the directive. Note: This directive may also be heard described described as ATEX '100a' or today as 'ATEX 95', after the enabling enabling articles of European treaties. treaties. ATEX User Directive 99/92/EC

This directive is concerned with the health and safety of workers with relation to potentially explosive atmosphe atmospheres. res. It places responsibilities on an employer. Typical responsibilities responsibilities include:

• • • • •

The assessment of risks Hazardous Area Classification Mitigation &/or removal of Risks Preparation of an Explosion Protection Document The provision of suitable warning signs for areas where explosive atmospheres may form

Note: This directive may also be heard described as ATEX '137', after the enabling article of the Treaty of Rome. Dangerous Substances and Explosive Atmospheres Regulations

From July 2006 employers must have completed the risk assessment, classification and documentation of their workplace and personnel.

Transfair Engineering: Designing Designin g and Prototyping …Circuits. Annex 2.

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12.12. CE Marking process The CE marking, type type approval and and Production Control Process Step 1: Identify the EU Directive(s) Directive(s) (see last chapter above) and EN Standards (see chapter 12.1.) that are applicable to your refrigerator types.

can download these directives free of charge from the European Union website and the main EN standards are mentioned in this booklet.

You

Step 2: Identify the conformity assessment procedure that must be taken. This could be self-declaration, involve testing, inspection or quality system

assessment by yourself or from a Notified Body or a combination of these. The conformity assessment procedure will differ depending on refrigerator type, EU Directives and EN standards in respect of which you will be use CE marking. This will be the date that the Directive and EN Standards comes into force. The majority of directives and EN standards are already in force. In these cases, it is an offence to place a product on the market without all needed type tests for CE marking because it indicates a presumption of conformity with all relevant Legislation. Legislation.

Step 3: Determine the dates by w hich you must take action.

Step 4: Identify if there are any Harmonised European Standards applicable to refrigerators and its components. The control that all EU Directives and

EN Standards are followed by component manufacturers, that they issue a declaration of conformity for their supplied components is useful. Whenever possible or appropriate, manufacturers should follow these harmonised EN standards.

Take appropriate measures of tests for type approval and production quality control on samples and on all refrigerators, respective tests on used components and materials to comply with these standards and identify needed quality control data and test reports.

Step 5: Ensure the product complies with all the essential requirements requirements of the Directive(s) and EN Standards.

Step 6: Identify whether independent assessment of your refrigerator type or of its components have conformity to the Directive , or some aspects of it,

is required from a Notified Body. This will be stated in the directive and is dependent upon the product you are CE marking. This could concerns components in contact with flammable refrigerant like Isobutane (Ex zone 0 and 1). You must not affix CE marking to your product until all necessary certifications have been obtained from the Notified Body, if needed.

Step 7: Maintain Technical Documentation Documentation required by the Directive(s) Directive(s) and EN Standards. Your

technical documentation should support your compliance with the requirements of the Directive and EN Standards. It is essential to retain this documentation for type approval and for the quality control that your production is in accordance to the type approval.

Step 8: Prepare the Declaration of Conformity and the required supporting evidence. The Declaration of Conformity along with the Technical

Documentation of type approval and essential quality control of production should be available to Competent Authorities (EU Members) upon request.

Step 9: Check that no other purely national requirements requirements exist

labelling or packaging requirements and waste regulation.

in the countries where the refrigerator will be sold. These may include national standards,

Step 10: Affix CE marking on your product and/or its packaging and accompanying literature as stated in the directive and the established EN standards. Remarks:

The EU Directive Directive and EN standards do not cover all quality relevant relevant aspects of a good household refrigerato refrigeratorr and good household refrigerator refrigerator manufacturing practices. Therefore Therefore it is useful to use further national standards (like the US or German ones) to cover a wider

areas of a good product and production control features, to use machine, assembly and process quality procedures as established in branches and sections to be useful to reach highest qualities, even to establish own quality standards in areas not fixed by standards or not sufficiently fixed, which you consider quality relevant and useful for your high quality product to be establish to guarantee product and production quality and state-of-art product and technology. All these could be added added to the type type test and production control as non obligatory part.


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Annex 1. Refrigerator and freezer appliances Several Energy Policy Scenarios (EPS) were set for cold appliances (i.e. refrigerators and freezers) and washing machines under the E-GRIDS project, to forecast the evolution of their energy efficiency and consumption up to 2010. Scenarios were built taking into considerations the energy policy measures at present under d iscussion between the European Commission and EU Member States. These consist in an energy labelling scheme - set according to the framework Directive 92/75/EEC and relevant implementing Directives - and an energy efficiency target - to be applied either voluntarily via a negotiated agreement with manufacturers or compulsorily via specific directives. directives. Seven EPS were built for cold appliances and three for washing machines. Once defined for the European Union as a whole, EPS EP S were applied also to Member States and to European economic area countries. For cold appliances, two labelling schemes - Labelling Option 1 and Labelling Option 2 - were set along with two efficiency targets, named Minimum Energy Efficiency Requirement and Voluntary Agreement Target, representing respectively the proposal for a mandatory legislation and for a negotiated agreement. The combination of these basic options leaded to the design of six scenarios for these products, namely: Baseline (BSL)

Energy Label Option 1 (EL1)

Energy Label Option 1a (EL1a)

Energy Label Option 2 (EL2)

This is the energy profile under the hypothesis of no new policy measure. Under this scenario, the only policies directly influencing the energy efficiency of the cold appliance market are the energy labelling and the mandatory minimum efficiency requirements. . It is generally assumed that the Directive 96/57/EC has no further direct influence on the market after its coming into force in autumn 1999, apart from preventing the return of less-efficient less-efficient appliances and that the influence of the labelling directive, assumed to stay unchanged, is continuing even if weakening. The energy-label scheme continues to exert its pressure to raise cold appliance efficiency, resulting in practically all models belonging to class A in 2010. This considers the introduction, from January 2004, of a revised energy labelling scheme, via the revision of Directive of Directive 94/2/EC, 94/2/EC, forecasting a complete rescaling of the A to G scale: the old energy efficiency class A is split in 5 new classes, from A to E; the old class B becomes the new F and the old classes from C downward (where still existing) become the new class G. This considers the introduction from January 2004 of the same revised energy labelling scheme set in scenario EL1, but with a less effective implementation due to the major confusion in consumers created by the downgrading of the models during the rescaling procedure. considers the impact of the introduction, again from January 2004, of a revised energy label scheme forecasting the maintenance maintenance of the present A to G scale with its EEI thresholds and the addition "on-top" of two new classes, called "A+" and " A++", to indicate the best models available on the market. Comparing the new scheme with the present energy labelling, class A is split into 3 classes (A, A+ and A++).

Energy Label Option 1 + Minimum considers the enforcing of an EU-wide E U-wide mandatory minimum energy efficiency Energy Efficiency Requirement requirement at EEI=55 from January 2007 (via the revision of the Directive 96/57/EC) along with the upgrading of the energy labelling directive 94/2/EC according to the labelling scheme described in scenario EL1 starting January 2004. In practice this scenario represents the building of mandatory minimum energy efficiency requirements on top of the revised labelling scheme. (EL1+MER)


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Energy Label Option 1a+Minimum Energy Efficiency Requirement This is the repetition of scenario "EL1+MER", in which the labelling scheme is applied less effectively (EL1a+MER) Co mmitment for cold appliances is negotiated with Energy Label Option 2 + Voluntary This assumes that a Voluntary Commitment industry, wherein the current C class appliances are phased out as per January 2004 Agreement Target followed by a "fleet" (i.e., weighted according to the sales of the d ifferent models for each manufacturer) average efficiency efficiency of new products, reaching the EEI=52 level by 2006. Contemporarily the labelling scheme described in scenario EL2 is enforced through the revision of Directive 94/2/EC. Again, the voluntary target is built in parallel (EL2+VAT) with the revised labelling scheme

Annex 1.1. European Commission DIRECTIVE 92/75/EEC of 22 September

1992 on the indication by labelling and standard product information of the consumption of energy and other resources by household appliances THE COUNCIL OF THE EUROPEAN COMMUNITIES, Having regard to the Treaty establishing the European Economic Community, and in particular Article 100a thereof, Having regard to the proposal from the Commission (1), In cooperation with the European Parliament (2), Having regard to the opinion of the Economic and Social Committee (3), Whereas measures should be taken progressively to achieve the internal market by 31 December 1992;

Whereas certain Member States already have their own voluntary schemes for energy labelling and the provision of other energy consumption information for household appliances; whereas one Member State has formally proposed introducing its own compulsory labelling scheme, and other Member States are considering c onsidering such introduction; whereas the existence of a number of compulsory national schemes would create barriers to intra-Community intra-Community trade; Whereas Article 130r of the Treaty requires prudent and rational utilization of natural resources; whereas the rational use of energy is one of the principal means by which this objective can be achieved and environmental pollution pollution reduced; Whereas the provision of accurate, relevant r elevant and comparable information on the specific energy consumption of household appliances may influence the public's choice in favour of those appliances which consume less energy, thus prompting manufacturers to take steps to reduce the consumption of the appliances which they manufacture; whereas it will also, indirectly, encourage the efficient use of these appliances; whereas, in the absence of this information, the operation of market forces alone will fail to promote the rational use of energy for these appliances; Whereas information information plays a key ke y role in the operation of market forces and it is therefore necessary to introduce a uniform label for all appliances of the same type, to provide potential purchasers with supplementary standardized information on those appliances' costs in terms of energy and the consumption of other resources and to take measures to ensure that potential purchasers who do not see the appliance displayed, and thus have no opportunity to see the label, are also supplied with this information; Whereas to this end the energy consumption of and other information concerning each type of appliance must be measured in accordance with harmonized standards and methods and t he application of these standards and methods must be monitored at the marketing stage; Whereas Directive 79/530/EEC (4) sought to promote these aims in the case of household appliances; whereas, however, only one implementing Directive for electric ovens has been adopted and few Member States have introduced this label; whereas it is therefore now necessary to learn from the experience acquired and to strengthen the provisions of that Directive; whereas Directive


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79/530/EEC must therefore be replaced and Directive 79/531/EEC (5) applying to those electric ovens o vens should be revised and subsequently integrated into the present scheme; Whereas a completely voluntary scheme would lead to only some appliances being labelled, or supplied with standard product information, with the risk that this might result r esult in confusion for some consumers; whereas the present scheme must therefore ensure that for all the appliances concerned, the energy consumption is indicated by labelling and standard product fiches are provided; Whereas household appliances use a wide variety of forms of energy, with electricity and gas being the most important; whereas this Directive must therefore in principle cover appliances using any form of energy; Whereas Council Directive 86/594/EEC of 1 December 1986 on airborne noise emitted by household appliances (6) provides for an indication of noise emission to be included on energy labels, where appropriate; whereas provision must therefore be made for the incorporation of any other information and labelling covered by Community schemes; Whereas only those types of appliances whose aggregate energy use is significant and which afford adequate scope for increased efficiency need be included, HAS ADOPTED THIS DIRECTIVE: Article 1

1. The purpose of this Directive is to enable the harmonization of national measures on the publication, particularly by means of labelling and of product information, of information on t he consumption of energy and of other essential resources, and additional information concerning certain types of household appliances, thereby allowing consumers to choose more energy-efficient appliances. This Directive shall apply to the following types of household appliances, even where these are sold for non-household uses: -

refrigerators, freezers and their combinations, washing machines, driers and their combinations, dishwashers, ovens, water heaters and hot-water storage appliances, app liances, lighting sources, air-conditioning appliances.

2. Further types of household appliances may be added to the list in this Article in accordance with Article 9 (b). 3. This Directive shall not apply to the rating plate or its equivalent affixed for safety purposes p urposes to such appliances. 4. For the purpose of this Directive: -

dealer means a retailer or other person who sells, hires, offers for hire-purchase or displays household appliances to endusers, supplier means the manufacturer or his authorized representative in the Community or the person who places the product on the Community market, information sheet means a standard table of information relating to the appliance in question, other essential resources means water, chemicals or any other substance consumed by an appliance in normal use, supplementary information means other information concerning the performance of an appliance, which relates to, or is helpful in evaluating, its use of energy or other essential resources.

5. There shall be no obligation to label or to provide fiches in respect of models of appliances of which production has ceased before the relevant implementing directive comes into effect, or second-hand appliances. Article 2

1. Information relating to the consumption of electric energy, other forms of energy and a nd other essential resources and supplementary information shall be brought to consumers' attention by means of a fiche and a label related to household appliances offered for sale, hire, hire-purchase or displayed to end-users.


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2. Details relating to the label and the fiche shall be defined by directives relating to each type of appliance adopted p ursuant to this Directive in accordance with Article 9. 3. Technical documentation shall be established which shall be sufficient to enable the accuracy of the information contained in the label and the fiche to be assessed. It shall include: -

a general description of the product, the results of design calculations carried out, where these are relevant, test reports, where available, including those carried out by relevant notified organizations as defined under other Community legislation, where values are derived from those obtained for similar models, the same information for these models.

4. The supplier shall establish the technical documentation described in paragraph 3. To this end it may use documentation already required on the basis of relevant Community legislation. The supplier shall make this d ocumentation available for inspection purposes for a period ending five years after the last product has been manufactured. Article 3

1. All suppliers placing on the market the household appliances specified in the implementing directives shall supply a label in accordance with this Directive. The labels used shall in all respects comply co mply with this Directive and with the t he implementing directives. 2. In addition to the labels, suppliers shall provide a product fiche. This fiche shall be contained in all product brochures. Where these are not provided by the supplier, he shall supply fiches with other literature provided with the appliance. The fiches used shall in all respects comply with this Directive and with the implementing Directives. 3. Suppliers shall be responsible for the accuracy of the labels and fiches that they supply. 4. The supplier shall be deemed to have given his consent to the publication of the information given on the label or the fiche. Article 4

In respect of labelling and product information, the following provisions shall apply: a) whenever an appliance specified in an implementing directive is displayed, dealers shall attach an appropriate label, in the clearly visible position specified in the relevant implementing directive, and in the relevant language version; b) the supplier shall supply the necessary labels free of charge, to dealers referred to in paragraph (a). Suppliers are free to choose their own system for delivery of labels. However, where a dealer sends a request for labels, the supplier must ensure that the requested labels are delivered promptly. Article 5

Where the relevant appliances are offered for sale, hire or hire-purchase by mail order, by catalogue, or by other means which imply that the potential customer cannot be expected to see the appliance displayed, the implementing directives shall make provision to ensure that potential customers are provided with the essential information specified in the label or the fiche before buying an appliance. Article 6

The implementing Directives shall make provision for the inclusion on the label or on the fiche of information i nformation on airborne noise, where such information is provided pursuant to Directive 86/594/EEC and of other public information relating to the relevant appliance, which is provided pursuant to other Community legislation. Article 7

Member States shall take all necessary measures to ensure that: a) all suppliers and dealers established in their territory fulfil their obligations under this Directive;


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b) if this is likely to mislead or confuse, the display of other labels, marks, symbols or inscriptions relating to energy consumption which do not comply with the requirements of this Directive and of the relevant implementing directives is prohibited. This prohibition shall not apply to Community or national environmental labelling schemes; c) the introduction of the system of labels and fiches concerning energy consumption is accompanied b y educational and promotional information information campaigns aimed at encouraging more responsible use of energy by private consumers. Article 8

1. Where the provisions of this Directive and of the implementing directives are satisfied, Member States shall neither prohibit nor restrict the placing on the market of the household appliances covered by an a n implementing directive. 2. Unless they have evidence to the contrary, Member States shall deem labels and fiches to comply with the provisions of this Directive and the implementing directives. They may require suppliers to furnish evidence within the meaning of Article 2 (3) concerning the accuracy of the information supplied on their labels or fiches when they have reason to suspect it is incorrect. Article 9

The measures relating to the establishment and operation of the scheme shall be adopted and adapted to technical progress in accordance with the procedure set out in Article 10. These measures are: a) the implementing directives; b) the addition of further household appliances to the list in Article 1 (1) where significant energy savings are likely to be achieved. Article 10

The Commission shall be assisted by a committee composed of representatives of the Member States and chaired by the representative of the Commission. Co mmission. The representative of the Commission shall submit to the committee a draft of the measures to be taken. The T he committee shall deliver its opinion on the draft within a time limit which the chairman may lay down according to the urgency of the matter. The opinion shall be delivered by the majority laid down in Article 148 (2) of the EEC Treaty in the case of decisions which the Council is required to adopt on a proposal from the Commission. The T he votes of the representatives of the Member States within the committee shall be weighted in the manner set out in that Article. The chairman shall not vote. The Commission shall adopt the measures envisaged if they are in accordance with the opinion of the committee. If the measures envisaged are not in accordance with the opinion of the committee, or if no op inion is delivered, the Commission shall, without delay, submit to the Council a proposal relating to the measures to be taken. The Council shall act by a qualified majority. If, on the expiry of three months from the date of referral to the Co uncil, the Council has not acted, the proposed measures shall be adopted by the Commission, save where the Council has decided against the said measures, by a simple majority. Article 11

After the expiry of a period of three years from the application of this Directive, the Commission shall make an assessment of the implementation implementation thereof and the results obtained. The assessment shall be the subject of a report to be submitted to the European Parliament and the Council. Article 12

The implementing directives shall specify: a) b) c) d)

the exact definition of the type of appliances to be included; the measurement standards and methods to be used in obtaining the information referred to in Article 1 (1); details of the technical documentation required under Article 2 (3); the design and content of the label referred to in Article 2, which as far as possible shall have uniform design characteristics;


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e) the location where the label shall be fixed to the appliance. Where appropriate they may provide for the label to be attached to or printed on the packaging; f) the content and where appropriate the format and other details concerning the fiche or further information specified in Article 3 (2). The information on the label shall also be included on the fiche; g) the information to be provided in the case of offers for sale covered by Article 5, and the manner in which it is to be provided. Article 13

Directive 79/530/EEC is hereby repealed, with effect from 1 January 1994. Directive 79/531/EEC shall be considered as implementing implementing this Directive for electric ovens; however Member States may refrain from its compulsory introduction, until a date set in a revised implementing directive concerning ovens passed in accordance with the procedure laid down in Article 10. Article 14

1. Member States shall adopt the provisions necessary to comply with this Directive by 1 July 1993. T hey shall immediately notify the Commission of these measures. They shall bring these provisions into force by not later than 1 January 1994. 2. When Member States adopt these measures, they shall contain a reference to this Directive or shall be accompanied by such reference on the occasion of their official publication. The methods of making such a reference shall be laid down by the Member States. 3. Member States shall communicate to the Commission the main provisions of domestic law which they adopt in the field covered by this Directive. Article 15

This Directive is addressed to the Member States. Done at Brussels, 22 September 1992. For the Council The President R. NEEDHAM (1) OJ No C 235, 10. 9. 1991, p. 5. (2) OJ No C 125, 18. 5. 1992, p. 172 and OJ No C 241, 21. 9. 1992. (3) OJ No C 49, 24. 2. 1992, p. 32. (4) OJ No L 145, 13. 6. 1979, p. 1. (5) OJ No L 145, 13. 6. 1979, p. 7. (6) OJ No L 344, 6. 12. 1986, p. 24. ANNEX I THE LABEL Label design

1. The label shall be in accordance with the following illustrations: Notes on label

2. The following notes define the information to be included: Note:

I. Supplier's name or trade mark. II. Suppliers model identifier.


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III. The energy efficiency class of an appliance shall be determined in accordance with Annex V. The approp riate letter shall be placed at the same level as the relevant arrow. IV. Without prejudice to any requirements under the Community Eco-label award scheme, where an appliance has been granted a 'Community Eco-label award' pursuant to Council Regulation (EEC) No 880/92 (1) a copy of the Eco-award mark (the flower) may be added here. The 'refrigerator/freezer label design guide' referred to below, explains how the Eco-award mark, may be included in the label. V. Energy consumption in accordance with standards referred to in Article 1 (2) but expressed in kWh per year (i.e. per 24 hours × 365). VI. Sum of net storage volume of all compartment co mpartmentss that do not merit a star rating (i.e. operating temperature > - 6 °C). VII. Sum of net storage volume of all frozen food storage compartments which merit a star rating (i.e. operating temperature = - 6 °C). VIII. Star rating of frozen food storage compartment, in accordance with standards referred to in Article 1 (2). Where this compartment does not merit any stars, this position shall be left blank. IX. Where applicable noise measured in accordance with Directive 86/594/EEC. NB: The equivalent terms in other languages to those described above are given in Annex VI. Printing

3. The following defines certain aspects o f the label: >REFERENCE TO A GRAPHIC>

Complete printing information is contained in a 'refrigerator/freezer label design guide' obtainable from: The Secretary of the Committee Co mmittee on Energy Labelling and Standard Product Information for Household Appliances Directorate-General for Energy DG XVII, Commission of the European E uropean Communities, 200 Rue de la Loi, B-1049 Brussels. (1) OJ No L 99, 11. 4. 1992, p. 1. ANNEX II THE FICHE

The fiche shall contain the following information. The information may be given in the form of a table covering a number of appliances supplied by the same supplier, in which case it shall be given in the order specified, or given in the description of the appliance: 1. Supplier's name or trade mark. 2. Supplier's model identifier. 3. Type of appliance as follows: Larger Fridge o Refrigerator/chiller o Refrigerator no star o o Refrigerator * Refrigerator ** o Refrigerator ***/ o Fridge-freezer *(***) o Upright freezer o Chest freezer o Multi-door or other appliance o 4. The energy efficiency class of the model as defined in Annex V, expressed as 'Energy efficiency class . . . on a scale of A (most efficient) to G (least efficient)'. Where this information is provided in a table this may be expressed by other means provided it is clear that the scale is from A (most efficient) to G (least efficient). 5. Where the information is provided in a table, and where some of the appliances listed in the table have been granted a 'Community Eco-label award' under Regulation (EEC) No 880/92, this information may be included here. In this case the row heading shall state 'Community Eco-label award', and the entry shall consist of a copy of t he Eco-award mark (the flower). This provision is without prejudice to any requirements under the Community Eco-label award scheme.


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6. Energy consumption in accordance with standards referred to in Article 1 (2) but expressed in kWh per year (i.e. per 24 hours × 365), described as: 'energy consumption XYZ kWh per year, based on standard test results for 24 h. Actual energy consumption will depend on how the appliance is used and where it is located.' 7. Net storage volume of fresh food storage compartment (5 °C) in accordance with standards referred to in Article 1 (2) omit for classes 8 and 9. 8. Net storage volume of frozen food storage compartment, in accordance with standards referred to in Article 1 (2) - omit for classes 1, 2 and 3. For Fo r class 3 appliances the net volume of the 'ice box'. 9. and 8. For classes 2 and 1 0 the net volume of each compartment should be listed, in accordance with standards referred to in Article 1 (2). 10. Star rating of frozen food storage compartment, if any, in accordance with standards referred to in Article 1 (2). 11. The mention 'no frost' may be included here when in accordance with the de finitions given in the standards referred to in Article 1 (2). 12. 'Power cut safe Z h' defined as 'temperature rise time' in accordance with standards referred to in Article 1 (2). 13. 'Freezing capacity' in kg/24 h in accordance with standards referred to in Article 1 (2). 14. 'Climate class' in accordance with the standards referred to in Article 1 (2). Where appliance is of 'temperate' climate class this may be omitted. o mitted. 15. 'Noise', where applicable, measured in accordance with Directive 86/594/EEC. Where an appliance contains compartments other than a single fresh food compartment and a single frozen food compartment, extra lines may be added at 7, 8, 8 , 9, 10, 11, 12 and 13 to include the information in respect of these compartments. In this case the naming and order of listing of the compartments shall be consistent. Where the design temperature of a compartment co mpartment does not conform to the star rating system, or the standard fresh food compartment compartment temperature (5 °C), this design temperature shall be given. The information contained in the label may be given in the form of a copy of t he label, either in colour or in black and white. In this case the further information given only in the fiche must still be included. Note: The equivalent terms in other languages to those described above are given in Annex VI. ANNEX III MAIL ORDER AND OTHER DISTANCE SELLING

Mail order catalogues and other printed communications referred to b y Article 2 (5) of this Directive shall contain the following information, given in the order specified: 1. Energy efficiency class (Annex II, point 4) 2. Energy consumption (Annex II, point 6) 3. Net volume of fresh food compartment (Annex II, point 7) 4. Net volume of frozen food compartment (Annex II, point 8) 5. Star rating (Annex II, point 9) 6. Noise (Annex II, point 14) Where other information contained in the product information fiche is provided, provided, it shall be in the form for m defined in Annex II and shall be included in the above list in the order specified for the fiche. The size and font, in which all the information referred to above is printed, shall be legible. Note: The equivalent terms in other languages to those described above are given in Annex VI. ANNEX IV CATEGORIES

The appliances covered by this Directive shall be divided into the following 'categories': 1. Household refrigerators, without low temperature compartments. compartments. 2. Household refrigerator/chillers, with compartments compartments at 5 °C and/or 10 °C. 3. Household refrigerators, with no-star low temperature compartments. compartments. 4. Household refrigerators, with low temperature compartments compartments *. 5. Household refrigerators, with low temperature compartments compartments **. 6. Household refrigerators, with low temperature compartments compartments ***.


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7. Household refrigerator/freezers, refrigerator/freezers, with low lo w temperature compartments *(***). 8. Household food freezers, upright. 9. Household food freezers, chest. 10. Household refrigerators and freezers with more than two doors, or other appliances not covered above. ANNEX V ENERGY EFFICIENCY CLASS

The energy efficiency class of an appliance shall be determined in accordance with the following Table 1: (not more valid, see Annex 1.1) Where: 'energy efficiency index' (expressed as a percentage) = annual energy consumption of appliance appl iance (1) / standard annual energy consumption of appliance 'standard annual energy consumption of appliance' appliance' (expressed (expressed in kWh/year) = M × adjusted adjusted net volume volume + N and adjusted net volume (expressed in litres) = net volume of fresh food compartment + ` × net volume of frozen food compartment. The values of M, N and ` are taken from Table 2. (not more valid) (1) In accordance with Annex I, note V. ANNEXE VI

EMPLACEMENT TABLE (not (not more valid)

Annex 1.2. European Commission DIRECTIVE 2003/66/EC of 3 July 2003 amending Directive 94/2/EC implementing Council Directive 92/75/EEC with regard to energy labelling of household electric refrigerators, freezers and their combinations (Text with EEA relevance)

THE COMMISSION OF THE T HE EUROPEAN COMMUNITIES, Having regard to the Treaty establishing the European Community, Having regard to Council Directive 92/75/EEC of 22 September 1992 on the indication by labelling and standard product information of the consumption of energy and other resources of household appliances (1), and in particular Articles 9 and 12 thereof, Whereas: (1) Electricity use by refrigerators, freezers and their combinations accounts for a significant part of total Community household energy demand. The further scope for a reduction of energy use by these appliances is substantial. (2) (2) The success of the labelling scheme introduced by Commission Directive 94/2/EC (2) , in conjunction with Directive 96/57/EC of the European Parliament and of the Council of 3 September 1996 on energy efficiency requirements for household electric refrigerators, freezers and combinations thereof (3) has led to a rise of the efficiency index of new refrigerators and freezers by over 30 % between 1996 and 2000. (3) About 20 % of the cold appliances sold in 2000 were in the most efficient class A, and in some markets the proportion was more than 50 %. The market shares of A class appliances are rising rapidly. Consequently, there is a need to introduce two additional classes, to be designated as A+ and A++, as an interim arrangement until a comprehensive comprehensive revision of the energy labelling classes takes place. (4) (4) The effect of labelling on energy efficiency will diminish, or disappear, unless further and more efficient classes are defined. (5) (5) Directive 94/2/EC should therefore be amended accordingly. By the same occasion, it will be possible to align that Directive on similar directives recently adopted, implementing Directive 92/75/EEC. (6) (6) The measures provided for in this Directive are in accordance with the opinion of the Committee set up under Article 10 of Directive 92/75/EEC, HAS ADOPTED THIS DIRECTIVE:


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Article 1

Directive 94/2/EC is amended as follows: 1.

In Article 1, paragraphs 2, 3 and 4 are replaced by the following: 2. The information required by this Directive shall be obtained by measurements made in accordance with harmonised standards adopted by the European Standardisation Bodies (CEN, CENELEC, ETSI) under mandate from the Commission in accordance with Directive 98/34/EC of the European Parliament and of the Council (*), the reference numbers of which have been published in the Official Journal of the European Union and for which Member States have published the reference numbers of the national standards transposing those harmonised standards. 3. The provisions in Annexes I, II and III requiring the giving of information relating to noise shall apply only where that information is required by Member States under Article 3 of Directive 86/594/EEC. This information shall be measured in accordance with that Directive. 4. In this Directive the definitions set out in Article 1(4) of Directive 92/75/EEC shall apply.

2. Article 2 is amended as follows: (a) In paragraph 1, the following subparagraph is added: ‘Where the information relating to a particular model combination has b een obtained by calculation on the basis of design, and/or extrapolation from other combinations, the documentation should include details of such calculations and/or extrapolations, and of tests undertaken to verify the accuracy of the calculations undertaken (details of mathematical model for calculating performance and of measurements taken to verify this model).’ (b) Paragraph 5 is replaced by the following: ‘5. Where the appliances are offered for sale, hire or hire purchase by means of a p rinted or written communication, or by other means which imply that the potential customer cannot be expected to see the appliance displayed, such as a written offer, a mail order catalogue, advertisements on the Internet or on other electronic media, that communication shall include all the information specified in Annex III.’ 3. Annexes I, II, III, and V are amended as shown in the Annex to this Directive. 4. Annex VI is deleted. Article 2

Member States shall allow the circulation of labels, fiches and communications referred to in Article 2(5) of Directive 94/2/ EC, containing the information as revised by this Directive, no later than 1 July 2004. They shall ensure that all labels, fiches and communications referred to in Article 2(5) of Directive 94/2/EC comply with the revised models, no later than 31 December 2004. Article 3

Member States shall adopt and publish the provisions to comply with this Directive no later than 30 June 2004. They shall immediately inform the Commission thereof. When Member States adopt those provisions, they shall contain a reference to this Directive or be accompanied by such a reference on the t he occasion of their official publication. Member States shall determine how such reference is to be made. Article 4

This Directive shall enter into force on the 20th day following that of its publication in the

Union.

Official Journal of the European


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Article 5

This Directive is addressed to the Member States. Done at Brussels, 3 July 2003. For the Commission

Loyola DE PALACIO Vice-President

_____________________________ (*) OJ L 204, 21.7.1998, p. 37; (1) OJ L 297, 13.10.1992, p. 16; (2) OJ L 45, 17.2.1994, p. 1; (3) OJ L 236, 18.9.1996, p. 36. ANNEX

(1) Annex I is amended as follows:

(a) under the heading ‘Notes on label’, the final sentence ‘NB: the equivalent terms in other languages to those described above are given in Annex VI’, is deleted; (b) under the heading ‘Printing’: (i) the following text is inserted after the illustration: ‘The indicator letter for A+ and A++ appliances shall be in accordance with the following illustrations, and shall be placed in the same position as the A indicator for A class appliances

’(ii) the final text, commencing with the words: ‘Complete printing information is contained in a “refrigerator/freezer “refrigerator/freezer label design guide” …’ is deleted. (2) Annex II is amended as follows:

(a) point 4 is replaced by the following: ‘4. The energy efficiency class of the model as defined in Annex V, expressed as “Energy efficiency class … on a scale of A++ (most efficient) to G (least efficient)”. Where this information is provided in a table this may be expressed e xpressed by other means provided it is clear that the scale is from A++ (most efficient) to G (least efficient).’ (b) point 8 is replaced by the following: ‘8. Net storage volume of frozen food storage compartment, and of chill compartment when available, in accordance with standards referred to in Article 1(2) — omit for classes 1, 2 and 3. For class 3 appliances the net volume of the “ice box”.’ (c) the following point 15 is added: ‘15. If the model is produced in order to be built-in, this should be stated.’ (d) the final Note is deleted. (3) Annex III is amended as follows:

The final Note is deleted. (4) In Annex V the following text is inserted after the title ‘ENERGY EFFICIENCY CLASS’: CLASS’: ‘PART 1: Definitions of Classes A+ and A++

An appliance shall be classified as A+ or A++, where the e nergy efficiency index alpha (I α) is within the ranges specified in Table 1.


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Table 1 Energy efficiency index

30 > Iα 42 > Iα ≥ 30 Iα ≥ 42 In Table 1

α

(Iα)

“Energy efficiency class”

A++ A+ A to G (see below)

where: AC = annual energy consumption of appliance (in accordance with Annex I, note V) SCα = standard annual energy consumption α of appliance SCα is calculated as

where:

Vc is the net volume (in litres) of the compartment (in accordance with standards referred to in Article 1(2)). Tc is the design temperature (in °C) of the compartment. co mpartment. The values of M α and Nα are given in Table 2 and the values of FF, CC, BI and CH are given in Table 3

Table 2 Type of appliance

Temperature of coldest compartment

Mα

Nα

1 Larger Fridge > – 6 °C 0,233 245 2 Refrigerator/chi Refrigerator/chiller ller > – 6 °C 0,233 245 3 Refrigerator no star > – 6 °C 0,233 245 4 Refrigerator * 0,643 191 ≤ – 6 °C * 5 Refrigerator ** 0,450 245 ≤ – 12 °C ** 6 Refrigerator ***/ 0,777 303 ≤ – 18 °C ***/*(***) 7 Fridge-freezer *(***) 0,777 303 ≤ – 18 °C ***/*(***) 8 Upright freezer 0,539 315 ≤ – 18 °C *(***) 9 Chest freezer 0,472 286 ≤ – 18 °C *(***) 10 Multi-door or other appliance (1) (1) (1) For these appliances, the temperature te mperature and star rating of the compartment with the lowest temperature will determine the values of M and N. Appliances with – 18 °C *(***) compartments shall be considered as fridge-freezers *(***). Table 3 Correction factor

Value

Condition

FF (frost-free)

1,2 For “frost-free” (ventilated) frozen food compartments 1 Otherwise CC (climate class) 1,2 For “tropical” appliances 1,1 For “subtropical” appliances 1 Otherwise BI (built-in) 1,2 For built-in appliances (1) of under 58 cm in width. 1 Otherwise CH (chill compartment) 50 KWh/y For appliances with a chill compartment of at least 15 litres 0 Otherwise (1) An appliance is “built-in” only if it is designed exclusively for installation within a kitchen cavity with a need of furniture finishing, and tested as such. If an appliance is not A+ or A++, it shall be classified in accordance with Part 2. PART 2: Definitions of Classes A to G

Diagramas de Mollier

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