CONVERSIONS ENGLISH TO METRIC 1 Btu 1 Btu/Hr 1 Btu/Hr-°F 1 Btu/Hr-Ft2-°F 1 Cfm 1 Cfm 5/9 (°F-32) 1 Foot 1 Square Foot 1 Cubic Foot 1 Gallon 1 Inch 1 Square Inch Centimeters 1 Cubic Inch 1 Inch H20 1 Pound 1 PSI 1 Watt Micron
= 252 Gram-calories =.252 K cal/Hr =.453 K cal/Hr.°C = 4.88 K cal/Hr-M2-°C = 28.32 Liters/Minute = 1.7 Cubic Meters/Hr = °C =.3048 Meter =.0929 Square Meter =.0283 Cubic Meter = 3.785 Liter = 2.54 Centimeters = 6.452 Square = 16.39 Cubic Centimeters = 2.54 Grams/CM2 = 453.6 Grams =.07031 Kg/CM2 = 3.413 Btu/Hr =.0000001 Meters
This Manual is published for informational purposes only and the information so provided should not be considered as all-inclusive or covering all contingencies. If further information is required, Thermo King Corporation should be consulted. Thermo King’s warranty will not apply to any equipment which has been so repaired or altered outside the manufacturer’s plants as, in the manufacturer’s judgment to effect its stability. No warranties, express or implied, including warranties of fitness for a particular purpose or merchantability, or warranties arising from course of dealing or usage of trade, are made regarding the information, recommendations, and descriptions contained herein. Manufacturer is not responsible and will not be held liable in contract or in tort (including negligence) for any special, indirect or consequential damages, including injury or damage caused to vehicles, contents or persons, by reason of the installation of a Thermo King product or its mechanical failure.
Table of Contents SAFETY Safety Cautions Responsible Refrigerant Handling
3 5
DIAGNOSTICS AND SERVICE TOOLS T-series Flow Diagram R-series Flow Diagram Diagnosing A System With an EPR Valve Diagnosing A System Without an EPR Valve EPR Non-Mechanical Cooling Problems Conditions That Cause High Discharge Pressure Conditions That Cause Low Discharge Pressure Diagnosing Using The Liquid Line Refrigeration System Access Tools
6 7 8 9 10 11 11 11 12-13
SERVICE PROCEDURES Compressor Service Valves 14 Gauge Manifold Installation (Standard Hose Fittings) 15-16 Gauge Manifold Installation (Low Loss Fittings) 17 Gauge Manifold Removal 18 Refrigerant Level Check 19-20 Adding Refrigerant 21 Charging An Evacuated Unit By Weight 22-23 EPR Valve Adjustment 24-27 Low Side Pump Down 28-29 Compressor Pump Down 30 Compressor Oil Pressure Check 31 Compressor Oil Level Check 32 Removing Compressor Oil 33 Adding Compressor Oil 34-35 Compressor Efficiency Test 36 Air Gap Adjustment 37 Testing For Air In System 38-39 Superheat 40-41 (Continued)
1
Table of Contents LEAK TESTING / SOLDERING / CLEAN UP Refrigerant Leak Check Tools 43 Leak Characteristics 44 Recommended Solders and Soldering Procedures 45-46 Refrigerant Recovery 47 Recovery From A Working Unit Without an Orit 10 Valve 48 Recovery From A Working Unit With an Orit 10 Valve 49 Recovery From Non-working Unit 50 System Evacuation and Clean Up 51-52 Multiple Evacuation 52 Compressor Oil Acid Test 53 Compressor Oil Filter Kit 54 Suction Line Filter 54
REFRIGERANT TYPES AND PROPERTIES Refrigerant Types and Properties
55
TEMPERATURE CHARTS Temperature Pressure Relationships Chart
56-57
GLOSSARY Bus Refrigeration Terminology
2
59-72
Safety DO NOT EXPOSE REFRIGERANT TO OPEN FLAME AS TOXIC FUMES MAY BE RELEASED
CAUTION: STAY CLEAR OF FANS AND OTHER MOVING PARTS
AJA785
CAUTION ALL SERVICE VALVES MUST BE BACK SEATED PRIOR TO REMOVING SERVICE PORT CAPS. NOTE: SOME VALVES MAY NOT HAVE A BACK SEAT.
HAZARDOUS VOLTAGE CAN CAUSE SEVERE INJURY OR DEATH
AJA786
3
Safety ALWAYS Wear Eye Protection and Protective Clothing When Handling Refrigerant
ALWAYS Wear Eye and Ear Protection When Servicing Refrigeration Units
AJA787
CAUTION Bus climate control systems are controlled by a thermostat that may cycle the unit ON or OFF with no prior warning. Condenser and evaporator fans will start when the unit is cycled ON by the thermostat. Do not wear loose fitting clothing or equipment around operating climate control systems. Always disconnect power to the unit before performing any maintenance procedures.
4
Safety Responsible Refrigerant Handling
Knowledge and Skills Vital to Human Health Scientific Evidence indicates that CFC refrigerants contribute to the depletion of the ozone layer and permits an increase in the harmful ultraviolet rays that reach the earth. Protecting the ozone layer through responsible refrigerant handling is the responsibility of all refrigeration and air conditioning service technicians.
ALWAYS HANDLE REFRIGERANT RESPONSIBLY AND PREVENT REFRIGERANT LOSS TO THE ATMOSPHERE.
•
•
•
Service Tools -- Use the proper service tools. Gauge manifold sets should include appropriate shutoff valves or disconnects near the end of each service line. Recovery Equipment -- Recovery equipment must be used. Proper recovering, storing and recycling of refrigerants is an important part of all service work. Service Procedures -- Recommended procedures must be used to minimize refrigerant loss.
•
Components may be isolated by closing service valves and performing system pump-downs.
•
Components unable to be isolated for service must be repaired only after refrigerant is properly recovered.
5
Diagnostics and Service Tools
AJA789
AJA788
“T” SERIES BUS CLIMATE CONTROL SYSTEM
6
Diagnostics and Service Tools
AJA791
“R” SERIES BUS CLIMATE CONTROL SYSTEM
7
Diagnostics and Service Tools Diagnosing a System with a EPR Valve SUCTION LINE Condition
A. COMPRESSOR SUCTION PRESSURE Low
High
Frosty/Cold
1.
Normal operation: Bus is controlling thermostat with light load and/or at higher speeds. 2. EPR valve set too high. 3. Airflow through evap. is low. • Air filter dirty. • Evaporator coil dirty. 4. EPR valve set too low: • Coil frosted up. 5. Evaporator Blower Motor. • Low Voltage. • Electrical Malfunction. • Fan Blades Damaged, Location, Direction.
1. Normal operation: • Heavy load on the evaporator 2. Expansion valve malfunction: • Fe el er bu lb mak ing poo r contact with suction line • Needle eroded—valve can not control properly • Adjustment has been incorrectly set (low superheat)
Dry/Warm
1. 2. 3.
1. Compressor malfunction: • Leaking discharge valves. • Leaking piston reeds. • Worn piston/sleeve assembly (blow-by). 2. Heavy load on evaporator: • C omp res so r t urn ing t oo slowly. • Belts slipping. • Clutch slipping.
4. 5. 6.
Low refrigerant charge. Restriction in liquid line. Expansion valve malfunction: • Inlet screen plugged. • Adjustment has been incorrectly set (high superheat). • Feeler bulb lost charge. Too much oil in system. Restricted suction line. Airflow through condenser coil too cold.
B. COMPRESSOR DISCHARGE PRESSURE
Suction Line Condition Does Not Apply
Low
High
1. 2.
1.
3.
4. 5. 6.
8
Low refrigerant charge. Light load on evaporator: • Bus interior temperature cool. • Dirty air filters. • EPR set too low—coil frosted up. • Airflow through evaporator is low for some reason. EPR valve incorrectly adjusted—too high causing low refrigerant flow. Compressor speed low. Airflow through condenser is cold. Restrictions to refrigerant flow: • Liquid line restricted • Suction line blockage
Airflow into the condenser is low or restricted: • Dirty coil. • D eb ri s i n t he c oi l in let . 2. Condenser fan or motor problem: • Motor running on low speed. • Motor not running— electrical malfunction. • Fa n bl ad e(s ) br ok en or incorrectly adjusted. 3. Restriction on high side of the system: • In-line service valve partially closed. 4. Non-condensables in system: • A ir, ni tro gen , an d ot her gases(?). 5. Hot air entering the condenser coil.
Diagnostics and Service Tools Diagnosing a System without a EPR Valve SUCTION LINE Condition Frosty/Cold
A. SUCTION PRESSURE Low 1.
2.
Dry/Warm
High
Restricted airflow through 1. Expansion valve malfunction: • Fe el er b ul b mak ing p oor the evaporator coil • Iced up evaporator contact coil • V alv e ad jus tme nt —ope n too much (low • Dirty evaporator coil superheat) • Plugged evaporator • Valve needle eroded filter 2. Overcharge of refrigerant Evaporator blower motor • Low voltage • Electrical malfunction • Fan blades— damage, location, direction
1. Low refrigerant charge 2. Restricted drier 3. Expansion valve malfunction: •Plugged screen—dirt, wax •Valve adjustment—closed too much (high superheat) •Internally frozen expansion valve—ice from moisture •Feeler bulb lost charge 4. Overfill of compressor oil 5. Restricted line in low side 6. Airflow through condenser coil too cold
1. Leaking discharge valve plates 2. Leaking piston reed 3. Worn piston/sleeve assembly— blow-by 4. Heavy load on evaporator 5. Compressor turning slowly 6. Belt or clutch slipping
B. DISCHARGE PRESSURE
N/A
Low
High
1. 2.
1. Overcharge of refrigerant 2. Air in the system 3. Airflow restricted across condenser coil: • Dirty condenser coil 4. Condenser motor: • Low voltage • E lec tri ca l mal fun ct ion • Fan blade damage/ location 5. Restriction in discharge side 6. Nitrogen left in system 7. Hot air across condenser coil
3. 4. 5. 6.
Low refrigerant charge Cold air across condenser coil Discharge valve plates leaking Piston reed leaking Inadequate compressor rpm Low side restrictions
N/A — Does not apply.
9
Diagnostics and Service Tools Non-Mechanical Cooling Problems
The suction line should feel cool or cool and moist AJA793
Check the suction line near the compressor. A cool, moist line is normal. When line condition and refrigeration pressures are near normal, look for problems outside of the refrigeration system.
AJA794
1. Excess Cooling Load. a. Open doors. b. Open windows. c. Open escape hatch. d. Large load of passengers. e. Damaged, deteriorated insulation. 2. Dirty return air filter and/or evaporator coil.
10
Diagnostics and Service Tools Conditions that can cause High Discharge Pressure 1. Air or non-condensables in system. 2. Restricted air flow across condenser, dirty condenser fins, slow fan speed, fans running backwards, etc. 3. A restriction in the high pressure line between the compressor and the receiver tank. 4. Overcharge of refrigerant during warm ambients. 5. Incorrect refrigerant. 6. High ambient temperature. 7. Heavy heat load in bus. Conditions that can cause Low Discharge Pressure 1. Low refrigerant charge. 2. Lowside restriction. 3. Worn compressor. 4. Cold ambient temperature. 5. Incorrect refrigerant. 6. Light heat load in bus. 7. EPR valve closing too soon. 8. Restricted drier.
Diagnosing Using the Liquid Line 1. The liquid line should be slightly warmer than the surrounding air. a. A low refrigerant charge may cause the liquid line to be warmer than normal. b. A liquid line restriction will cause the line to become cold after the point of restriction.
The Liquid line should be warmer than the surrounding air
AJA795
11
Diagnostics and Service Tools Refrigeration System Access Tools
ACCESS VALVE ACTUATOR TK 204-625
Use the access valve actuator to remove refrigerant or oil from 1/4 in. male flare fittings.
Taking a compressor oil sample
QUICK DISCONNECT ACCESS VALVE-TK 204-679 Low loss fittings and quick disconnects keep pressure in the gauge lines when the gauge manifold is removed from the system.
12
Diagnostics and Service Tools
AJA799
GAUGE ADAPTER FITTING TK 204-626 Use the gauge adapter fitting with pressure gauges to read pressures with minimal refrigerant or oil loss.
Compressor Oil Pressure
Receiver Tank Pressure
AJA804
13
Service Procedures COMPRESSOR SERVICE VALVES
AJA800 Full Out-Valve Back Seated
AJA801 In 1/2 way-Valve Mid-seated
AJA802 Full In-Valve Front Seated
AJA803 Full Out,1/4 turn in“Cracked” Open to Service Port
WARNING: Service valve stems and service ports must be properly capped and torqued with seals or O-rings installed. STEMS AND PORTS NOT PROP- ERLY CAPPED WILL LEAK REFRIGERANT.
Service Valve
Service Port Cap
Stem Cap
AJA805
The suction service valve (SSV) is generally larger than the discharge service valve (DSV) but is built the same.
14
Service Procedures
Suction Service Valve
Discharge Service Valve
AJA806
Gauge Manifold Installation (Standard Hose Fittings) 1. Remove the large service valve stem caps from the 2. 3. 4.
5.
discharge and suction service valves. DO NOT remove the small service port caps! Turn both service valves fully counterclockwise to back-seat the valves and close the service ports. Remove the small service port caps from both service valves. Attach the low pressure gauge line to the suction service port. Leave the fitting loose. (This loose connection will be used to purge air from the gauge manifold.) Attach the high pressure line to the discharge service port and secure the line finger tight. (Continued)
15
Service Procedures 6.
7.
Turn the discharge service valve stem 1/4-turn clockwise to open the service port. (The high pressure gauge should indicate pressure in the discharge side of the system.) Open the high side hand valve on the gauge manifo-
SSV valve back seated
connect to manifold DSV valve cracked
AJA807
fold. Purge air from the gauge manifold service line (yellow) and tighten the line fitting to the manifold hose anchor. 8. Open the low side hand valve on the gauge manifold and allow a small amount of refrigerant to escape from the loose suction service port fitting and tighten hose on SSV (This will purge air from the gauge manifold and the red and blue gauge manifold lines). 9. Close both gauge manifold hand valves. 10. Turn the suction service valve stem 1/4-turn clockwise to open the service port. (The low pressure gauge should indicate pressure in the suction side of the system.) WARNING! NEVER operate the compressor with the discharge service valve front seated. The valve is front seated when the service valve stem is turned fully clockwise.
16
Service Procedures Gauge Manifold Installation (Low Loss Fittings) 1. Remove the large service valve stem caps from the discharge and suction service valves. DO NOT remove the small service port caps! 2. Turn both service valves fully counterclockwise to back seat the valves and close the service ports. 3. Remove the small service port caps from both service valves. AJA808 4. Attach the high pressure line (red) to the discharge service port and secure the line finger tight. 5. Turn the discharge service valve stem 1/4-turn clockwise to open the service port. (The high pressure gauge should indicate pressure in the discharge sid e of the system.) 6. Open both hand valves on the gauge manifold. 7. Purge the gauge manifold yellow service line. This is accomplished by slowly screwing a 1/4 inch flare fitting into the low loss fitting on the gauge manifold yellow service line. Allow a small amount of refrigerant to escape from the service line and then remove 1/4” flare fitting. Tighten the yellow service line fitting to the gauge manifold hose anchor. (See illustration) 8. To purge the gauge manifold and low pressure line, slowly screw a 1/4 inch flare fitting into the low loss fitting on the low pressure (blue) line. 9. Close both gauge manifold hand valves. 10. Install the gauge manifold low pressure line (blue) on the suction service port. 11. Turn the suction service valve stem 1/4-turn clockwise to open the service port. (The low pressure gauge indicates pressure in the suction side of the system.), WARNING! NEVER operate the compressor with the discharge service valve front seated. The valve is front seated when the service valve stem is turned fully clockwise. 17
Service Procedures Removing the Gauge Manifold NOTE:Minimize oil and refrigerant transfer. Use the fol- lowing gauge manifold removal procedure to maintain system integrity without the need to use a different gauge manifold for each type of refrigerant. 1. Jumper the low pressure cut out. 2. Operate the unit in the cool mode. 3. Back seat the discharge service valve. 4. Open both manifold hand valves. 5. Front seat the suction service valve and pump down the compressor to a 20” vacuum. Turn the unit off. 6. Establish compressor crankcase pressure between 1 and 3 psig. 7. Remove the gauge line from the suction service valve and cap the service port. 8. Remove the gauge line from the discharge service valve and cap the service port. 9. Back seat the suction service valve and cap the valve stem. 10. Cap the discharge service valve stem. 11. Secure all manifold lines to manifold hose anchors when the manifold is not in use. 12. Remove low pressure jumper and reconnect wiring.
18
Service Procedures Check Refrigerant Charge Level The charge level is very important to the efficient operation of the unit, therefore, it must be checked as part of the MONTHLY MAINTENANCE. This service procedure addresses the method for checking and adding charge as necessary. Purpose: To have a charging procedure which will allow an air conditioning technician to properly charge the system, without over charging or under charging it, in all weather conditions. Scope: This bulletin supersedes all previous charging bulletins. This procedure only covers T-Series units with sight glass indicators with a floating ball in the upper half of the receiver tank. Procedure: During a visual check, when the receiver tank ball is not floating in the upper sight glass, use the following "Top Off Procedure" to check and replace the required reserve charge (Locate and repair all leaks to stop further leakage). 1. Follow standard Thermo King procedures and connect your service gauges to the compressor service valves or standard access ports. Be sure to purge the air from your lines. 2. Start the bus and run the engine in the FAST IDLE MODE with the air conditioning turned on. This should be between 1200 and 1600 compressor rpm. For buses without the fast idle mode, elevate engine speed until compressor speed is between 1200 and 1600 rpm. NOTE: On some applications, a regular low idle engine speed will not allow you to see the correct refrigerant level and may result in an improperly charged system. 3. If the system has not been running you must run the system long enough to separate the compressor oil from the refrigerant AND pull the bus INTERIOR down (or up) to WITHIN THE 65 TO 75 DEGREE RANGE. This may take sometime if conditions are extreme, but a minimum of 15 minutes should be allowed before checking the charge level. 4. If the COMPRESSOR DISCHARGE PRESSURE is not ABOVE 250 psig, use a piece of cardboard to part ially cover the condenser coil inlet grille.Do not shut off condenser fans to raise pressure. This will drive the pressure up into the range REQUIRED FOR CHECKING AND CHARGING. 19
Service Procedures 5.
Once the conditions of steps 2, 3 and 4 above have been met, check the ball in the receiver tank upper sight glass. The proper charge level for this "Top Off" procedure will have the ball floating at the top of the upper receiver tank sight glass. 6. If the ball is not at the top of the sight glass, follow standard Thermo King charging methods, add charge to the system until the ball floats to the top of the sight glass. Note: If the system is low on charge, leak check and repair accordingly. Note: Add liquid refrigerant on the low side, increasing the suction pressure no more than 25 psi. When charging the system from a properly "Evacuated" condition, (Refer to "Evacuating a System" procedure), we strongly recommend that you weigh in the charge. This will save you time and ensure the full reserve charge. NOTE: Refer to unit maintenance manual specification section for proper weight charge. CAUTION: Air in the system will tend to collect in the receiver tank forcing the refrigerant level down. If you have air in your system, floating the ball may over- charge the system. Check your system for air before letting it go back into service. CAUTION: AIR IN THE SYTEM WILL ELEVATE OPER- ATING PRESSURES AND TEMPERATURES, which in turn will begin a severe degradation process. AND, which, if left unchanged, will result in system failure which is NOT COVERED UNDER YOUR THERMO KING WARRANTY.
20
Service Procedures Adding Refrigerant Today’s refrigerants must be added as a liquid. Use this procedure to add liquid refrigerant to the low side of an operating unit. Bus should be at fast idle mode, 1200 to 1600 RPM in compressor. 1. Cra Crack ck the the discha discharge rge servi service ce valve valve (DSV) (DSV) and and open itit to the service port. 2. Mid Mid-se -seat at the the suct suction ion serv service ice val valve ve (SSV). (SSV). 3. Set the refrige refrigerant rant bottle to withdraw withdraw liquid refrige refrigerant. rant. 4. Ope Operat rate e the unit unit in cool cool and and read read the suct suction ion press pressure. ure. 5. Slo Slowly wly open open the the gauge gauge manif manifold old low low press pressure ure hand hand valve until suction pressure rises approximately 25 psig above the normal operating pressure. 6. Gau Gauge ge must must show show 250 250 lbs. lbs. discharg discharge e pressur pressure e with with R22 and R-407C refrigerant. Gauge must show 150 lbs discharge pressure with R12 and R-134A refrigerant. 7. Clo Closel sely y watch watch the receiv receiver er tank tank top sight sight glass glass.. ImmeImmediately stop adding refrigerant when refrigerant is seen at the top of the sight glass. 8. Clo Close se the the refri refrigera gerant nt bott bottle le hand hand val valve. ve. 9. Rem Remove ove the the gauge gauge mani manifol fold d in the the recomm recommend ended ed manmanner.
Adding Refrigerant
SSV Mid seated DSV Cracked open
AJA809
21
Service Procedures Charging an Evacuated Unit by Weight 1. 2. 3.
Installl a gaug Instal gauge e manif manifold old.. Keep Keep the the unit unit off. off. Recove Rec overr the refri refriger gerant ant and and evacua evacuate te the syst system. em. Place Pla ce the the refrige refrigeran rantt bottle bottle on a scal scale e and atta attach ch the manifold’s service line. 4. Ope Open n the bottl bottle e to withd withdraw raw liqu liquid. id. Purge Purge air air from from the service line as required. 5. Rec Record ord total total refr refrige igerant rant and and conta containe inerr weight. weight. 6. Che Check ck the the unit data data plat plate e or unit unit Mainte Maintenanc nance e Manual Manual for refrigerant weight required. 7. Mid seat seat the the compre compresso ssorr discha discharge rge servi service ce valve valve.. 8. Ope Open n the dis discha charge rge hand hand valv valve e all the way way on the gauge manifold and begin charging the unit. Refrigerant flow can be felt as small pulsations on the manifold service line. 9. Wat Watch ch the the scale scale and and close close the the hand valv valve e at the refr refrigigerant bottle when the correct charge has been added. 10. If refrigerant refrigerant flow stops before before charging is complete, complete, close discharge manifold hand valve and return the DSV to the cracked position. Add Liquid refrigerant into the SSV with the unit running as described in the Adding Refrigerant Procedure.
22
Service Procedures UNIT NOT RUNING
Drawing shows liquid refrigerant being added. SSV valve cracked open DSV valve mid-seated
AJA810
To charge an evacuated unit, add liquid refrigeran t to the receiver tank or through the discharge service valve. KEEP THE UNIT OFF. To charge a running unit, add liquid through the suction service valve. Control refrigerant flow to increase suction pressure approximately 25 psi.
Drawing shows liquid refrigerant being added.
UNIT RUNNING IN COOL SSV valve mid-seated
DSV valve cracked open
AJA811
23
Service Procedures Date: October 3, 1997 Service Bulletin Subject: Evaporator Pressure Regular (EPR) Adjustment Application: ALL Thermo King Bus units which are equipped with an EPR valve. (THIS PROCEDURE SUPERSEDES ALL PREVIOUS EPR VALVE ADJUSTMENT PROCEDURES)
Read Me First: The purpose of the EPR valve is to limit how low the pressure inside of the units evaporator coil will go. Holding the pressure at or above a set value also limits how low the coil temperature can fall.The pressure and temperature, once they have moved above the EPR valve setting, are dependent on the heat load being accepted by the unit. The EPR valve should not allow the pressure to fall below th e point of condensate freezing on the coil. To achieve that, the EPR valve will stop or restrict the flow of refrigerant to hold the pressure at or above the set point of the valve. Once this valve is properly set it does not get out of adjustment. The valve is factory set, but should be checked as part of the delivery checkout procedure. Adjustment if required, should be done by qualified personnel only. NOTE: Improper adjustment of this valve may cause damage to the system. NOTE: The ambient temperature and the bus interior must be above 80 F. CAUTION: Do Not attempt to adjust this valve if the ambient and bus interior temperatures are not above 80 F. Improper setting, and damage to the system may result.
24
Service Procedures Procedure For Checking And Adjusting The EPR Valve. 1. Install service gauges on the compressor and jumper the low pressure cutout. 2. Install a compound gauge on the pressure tap on the evaporator side of the EPR valve. 3. Replace all covers removed to install the compound gauge on the EPR valve. 4. Be careful not to pinch the hose on the compound gauge, seal all areas that will leak air when the unit is running. 5. Start the Bus, run at either fast or slow idle for at least ten minutes. This will return the oil to the compressor. 6. If necessary, turn the heat mode on and raise the interior temperature above 80 F. Then r eturn the unit to the cool mode. Note: you will need two people to finish the test. 7. One person raises the engine/compressor speed to maximum governed speed. (If not governed 2/3-throttle point.) Caution: You must increase the compressor speed (step #7). If you don’t, the set point will not be cor- rect and damage to the refrigeration system may result. (continued)
25
Service Procedures 8. 9.
10.
11.
12.
13.
26
When the Bus engine is maintained at high speed, shut off the evaporator fan motor(s). Watch the compound gauge installed on the EPR valve. The pressure will drop and stabilize. T his should take one minute or less. When the compound gauge stabilizes this is the set point. The set point should be at the pressure stated on the following table. There should be a large difference between the compound gauge [EPR valve] and the suction ser vice valve gauge readings (20-30 PSI or the compressor may even go into a vacuum). Note: You may need to jumper the low side pres- sure cutout switch to be able to complete this set- ting procedure. Lower the engine/compressor speed to high idle and switch the evaporator fan motor(s) back on. Run the unit at high idle for more than 5 minutes to clear the liquid refrigerant in the coil or compres- sor damage may occur. If the EPR valve requires adjustment, turn the adjusting screw CW to increase the setting (raising coil temperature/pressure) and CCW to decrease the setting (lowering the coil temperature/pressure). Do not turn more than 1/4 turn at a time.
Service Procedures 14. After every adjustment all covers must be reinstalled and then run for at least 5 minutes before retesting. 15. If the setting is still incorrect, repeat steps 13 and 14. 16. When the setting is correct, recheck the setting twice (steps #6 thru #13], you should get the same reading. 17. When the test is complete remove all gauges, jumper wires and reinstall all covers back. 18. Check the refrigerant charge, oil level and return to service.
Type of EPR valve:
ORIT-15 Large type
ORIT-10 Small type
Refrigerant:
Set pressures:
Set pressures:
R-134a
24 +/-1 psig
24 +/-1 psig
R-22
50 +/-1 psig
50 +/-1 psig
R-407C
50+/-1 psig
50 +/-1 psig
R-12
27+/-1 psig
27 +/-1 psig
Filed: F:\Bus\Usrefdat\procedur\eprset.doc
27
Service Procedures Low Side Pump Down Purpose: To test for internal (high side to low side) leaks and to perform service on the low side without refrigerant loss. 1. Check gauge manifold hose gaskets. They must not leak during this test or the system may be contaminated with air! 2. Jumper out low pressure cut out (LPCO). 3. Install a calibrated gauge manifold on the SSV & DSV. 4. On units with Orit 10 EPR valve, mount the service hose from the manifold gauge to the EPR service port. Then open the low side hand valve. On units with the Orit 15 EPR valve, shut the hand valve on the pilot valve. 5. Run the unit in cool for ten minutes or longer. 6. Front-seat the receiver tank outlet valve (RTOV). 7. Pump down the lowside to a 25" vacuum. 8. Stop the unit. 9. Observe the low side gauge. Low side pressure should remain below a 15" vacuum for two minutes or longer. • If pressure rises to zero and stops, there is a low side leak to the atmosphere. • If pressure continues to rise above zero, the following may be responsible • Refrigerant boiling out of the compressor oil. (Restart unit and pump down to 25" vacuum.) • High side to low side leaks at the compressor discharge valve plates or hot gas bypass valve if equipped. The following services can be performed with the low side pumped down and a slight positive pressure established on the low side: • Add or remove refrigerant oil. • Clean the expansion valve screen. • Change the expansion valve. • Replace the liquid line drier. • Replace the compressor oil filter. • Replace lowside tubing. • Replace EPR valve.
28
Service Procedures
Shut The Hand Valve on the Pilot Valve (Orit 15 only)
AJA813
29
Service Procedures Compressor Pump Down Purpose: • • • 1. 2. 3. 4. 5. 6.
Service the compressor safely with a minimum loss of refrigerant. Check compressor for external leaks to the atmosphere (if reading rises to zero and stays). Check for internal leaks in the compressor (if reading rises above zero). Install gauge manifold set to monitor system pressures. Bypass the Low Pressure Cutout (LPCO) to prevent the clutch from disengaging. Start and run the unit for 15 minutes to stabilize pressures. Front seat the suction service valve and pump down the compressor to a 20” to 25” vacuum. Stop the unit. The crankcase pressure should remain below 0 PSI for at least 15 seconds.
To Remove Compressor: a. Pump down the compressor to a 15 inch vacuum. b. Stop the unit. c. Immediately front seat the discharge service valve. d. Balance pressures through the gauge manifold to 1or 2 psig. e. If 1 to 2 psig cannot be established, the refrigerant must be recovered or a lowside pump down must be performed. NOTE: Pumping down the compressor causes refriger- ant to boil off in the compressor. It may be necessary to start and stop the unit several times before the com- pressor will hold a vacuum. NOTE: If you are going to service the compressor, bleed some positive pressure, through the gauge man- ifold, into the compressor. If you open the compressor to the atmosphere while it is in a vacuum, you will draw air into the compressor and contaminate the system.
30
Service Procedures Compressor Oil Pressure Check 1. 2.
3.
4. 5.
Install suction pressure gauge Install gauge on compressor port “A”. It may be necessary to pump down system and use a gauge line with a schrader valve depresser. With unit running observe gauge reading at compressor oil pump, this is both suction pressure and compressor oil pressure. Read the suction pressure gauge. Calculate oil pressure using the following sample as a guide: Pressure from port “A” 60 PSI Suction pressure gauge reading - 25 PSI Net oil pressure* = 35 PSI* *Recommended net oil pressure should be between 15&45 PSI.
60 PSI
15-45 PSI Suction pressure Gauge
Schrader Valve in fitting Port “A”
31
Service Procedures Compressor Oil Level Check The compressor oil level cannot be accurately checked unless the unit has been operating for a period of not less than 15 minutes and has air flow over the evaporator that has attained a temperature of 70 to 80 F (21 to 27 C). This will assure that the oil in the unit system has warmed sufficiently to thin down and flow more readily through the system, thus ensuring a more valid reading. Check oil level and add oil if required when the following operations have been performed 1. A major refrigeration component has been removed or replace. 2. After recharging the unit. 3. After repair of a major refrigerant leak. 4. If a maintenance inspection procedure indicates the system oil level is low. NOTE: The unit does not consume oil. If the unit requires additional oil, it is because there has been a leak or a major repair to the system. Check oil level by using the following procedure: 1. Start the unit. 2. If the bus temperature is above 70 F (21.1 C), put the unit on COOL cycle and proceed to step 4. 3. If the bus temperature is below 70 F (21.1 C), put the unit on HEAT cycle and operate until the bus temperature attains a minimum of 70 F (21.1 C). Proceed to step 4. 4. Operate unit on COOL with 70 to 80 F (21 to 27 C) air over the evaporator for a minimum of 15 minutes. (continued)
32
Service Procedures 5.
Ensure the unit is in COOL cycle. Check the oil level with a flashlight while unit is operating. The compressor oil level sight glass should indicate 1/4 to 1/2 full. If indicator reading is low, oil must be added; proceed to Adding Compressor Oil. If indicator reading exceeds 1/2 level, oil must be removed; proceed to Removing Excess Oil. NOTE: The compressor must be pumped down if oil is added or removed. Pumping down the compressor causes the oil to indicate lower than during normal operation. Therefore, it is necessary to carefully note the difference in oil level between normal operation and when it is pumped down. Be sure to take this dif- ference into account when adding or removing com- pressor oil.
Removing Excess Oil 1.
2.
3.
4. 5.
Pump the compressor down. Refer to Low Side Pump Down Procedure or Compressor Pump Down Procedure. After stopping the compressor use the manifold gauge set to adjust the compressor (low side) pressure to 1 to 3 psi. (Pressure measured at the compressor suction service valve port). Loosen the drain plug (DO NOT REMOVE) allowing the oil to drain SLOWLY while watching the level in the compressor sight glass. NOTE: Heavy foaming of the oil as it leaves the compressor may indicate an excess of refrigerant in the oil. Run the system longer to insure a warm sump. Then recheck level. Tighten the drain plug and leak check. Run the system again and confirm the refrigerant charge level as well as recheck the oil level before allowing the bus to return into service.
33
Service Procedures Adding Compressor Oil 1. 2. 3.
4.
5.
6. 7.
8.
9.
10.
11.
34
Estimate how much oil will be required to make the level adjustment. Perform a compressor pump down by following the procedure indicated in this manual. Stop the bus engine, turn off the bus power and operating safety switch to insure that no one can start the bus while you are working on it. Front seat the compressor discharge service valve in addition to the suction service valve which was front seated in step #2 above. Balance pressures to establish positive pressure and recover excess refrigerant pressure. Confirm which oil is to be added to this system. Hook up a vacuum pump to your service gauges which were connected in step #2. Hook up another service both hose to the oil pressure valves frontport on top of the compresseated sor oil pump at the top rear of the compressor. Open the oil container. AJA815 Balance System Never leave oil containers open to the air for long periods of time. Put the hose from the oil pressure port into the container of oil. Turn on the vacuum pump and lower the pressure inside of the compressor to pull the oil into the sump through the compressor oil pump until the oil level is correct. Secure the oil pump pressure port and replace the cap. Continue evacuating the compressor sump area to remove all air and noncondensable gasses which were pulled in with the oil.
Service Procedures
12. When evacuation is complete, back seat all system valves, start the bus and A/C system and recheck the compressor oil level. 13. Confirm the system refrigerant charge level, following the correct procedures (noted in this manual) adjust charge as required before allowing the bus to return to service. CAUTION: Always confirm which oil is in the system you are servicing before you add oil. The wrong oil can cause severe damage. 1.
Oil Drain Plug
7.
Service Manifold Gauge
2.
Oil Fill Plug
8.
Micron Gauge
3.
Oil Pump Port
9.
Vacuum Pump
4.
Shut-off Valve
10.
Measuring Container Filled w/ Compressor Oil
5.
Discharge Service Port
11.
Compressor Oil Sight Glass
6.
Suction Service Port 35
Service Procedures Compressor Efficiency Test Purpose: • Check the discharge valve plate reeds for leakage. • Check the piston reeds for leakage. • Check the piston to sleeve clearance. 1. Install gauge manifold set to monitor system pressures. 2. Bypass the Low Pressure Cutout (LPCO) to prevent the clutch from disengaging. 3. Start and run the unit at fast idle for 15 minutes to stabilize system pressures. EXAMPLE: On an 80 F day, your discharge pressure will be approximately 240 psig.(With R-22 or 407-C refrigerant.) 4. Cover the inlet side of the condenser coil to increase the discharge pressure 70-100 psig higher than normal. EXAMPLE: If your discharge pressure is 240 psig after 15 minutes of operation, increase it 310-340 psig. 5. Front seat the suction service valve. 6. When the compressor reaches a 10” vacuum, observe the discharge pressure. It should read as follows: A. R-12 & R-134a 125 psig or higher B. R-22 & R-407C 190 psig or higher NOTE: If you can’t increase the discharge pressure higher than normal, check the following: • Piston reed(s) or discharge valve plate reed (s) may be defective. • Compressor may have excessive piston to sleeve clearance. • Unit may be low on refrigerant. NOTE: If the compressor will not pull at least a 15” vac- uum, the piston reed may be defective or the piston to sleeve clearance may be excessive. If the compressor will pull a deep vacuum, but not stay below 15” of vacuum for at least 15 seconds after unit is turned off, the discharge valve reed(s) are defective.
36
Service Procedures Air Gap Adjustment 1. 2.
Loosen the lock nuts on the three adjustment screws. Using a 3/32 in. (2.4 mm) Allen wrench, turn each adjustment screw in clockwise (CW) until the armature bottoms out on the pulley.
Allen Screw Bottoms Out Armature
AJA817
3.
4. 5.
Back each adjusting screw out counterclockwise (CCW) 1-1/2 turns. This equals a .045 in. (1.143 mm) air gap. Double check air gap with feeler gauge per procedure in step 3 of checking air gap (new clutch only). Tighten the lock nuts. Make sure the adjusting screw does not turn by holding it with an Allen wrench. Wrench Tightening Locknut
3/32 in. (2.4 mm) Allen Wrench
6.
Check the air gap in three different places 120° apart. NOTE: The clutch should be checked monthly during high usage periods
37
Service Procedures Testing For Air In The System Ice Bath Sample Method Test This inexpensive method requires that a small amount of the system’s refrigerant be placed in a sample bottle and the bottle submerged in an ice bath. Required Tools Manifold Set, Sampling Bottle, Micron Gauge, Vacuum Pump, Thermometer, Ice Water Bath Consisting of 75% Ice, Set of Refrigeration Wrenches to open and close valves. Manifold Set Hookup Procedure Attach manifold set as follows: 1. Connect low side hose to sample bottle. 2. Connect center hose to receiver tank service valve. Valve remains closed. 3. Connect high side hose to evacuation pump. CAUTION: If hoses are not connected properly, gauge readings will be inaccurate. Ice Bath Test Procedure 1. Open manifold gauges and evacuate all hoses, manifold and sample bottle to 500 microns. CAUTION: Check for leaks in the system.
AJA820
AJA819
(continued) 38
Service Procedures 2.
Run the compressor to circulate any air that may be in the system. 3. Close the high side gauge valve to isolate the micron gauge and pump. 4. Open the receiver tank service valve to a count of four (4). Then close the valve and count four (4) again. 5. Then close the low side gauge valve. 6. Place the sample bottle into the ice bath for 15 to 20 minutes. Stir the ice mixture occasionally. NOTE: An ice water bath must be 75% ice in small pieces and it should completely cover the sample. The smaller the tank, the faster the temperature will equal that of the ice water bath. CAUTION: The procedure of taking the sample is extremely important to avoid contaminating the sample. 7. Compare low side gauge reading with your pressure/ temperature chart for 32F (0C). R-12 = 30 psig (207.5 kPa) R-22 = 57.5 psig (396.4 kPa) R-134a = 27.3 psig (188.3 kPa) R-407c = 50.9 psig (356.3 kPa) READING MUST BE +/- ONE (1) psig (7 kPa). If pressures exceed specifications, the refrigerant must be reclaimed and the unit totally evacuated according to proper evacuation procedures. After the system has been evacuated, leak tested, and recharged with clean refrigerant, reconfirm the system operation. If system operation is satisfactory, return the bus to service. CAUTION: If the air and other non-condensables are not removed, premature system failure will result.
AJA822
AJA821
39
Service Procedures Superheat Expansion Valve Measure (Superheat) NOTE. Be sure the temperature reading instrument and compound pressure gauge are accurately calibrated. Procedure: 1.
2.
3. 4.
Pump down the low side into the receiver tank. Open the receiver tank outlet valve to bleed the pressure back to 1 to 3 psi in low side. Install pressure gauge in the expansion valve external equalizer line. This will indicate the pressure directly and accurately. Use the Temperature Pressure Chart in this manual to convert the pressure reading into temperature. Measure suction line temperature at point where feeler bulb is attached.(See drawing) Open the receiver tank outlet valve and operate the unit for 15 minutes. Subtract temperature reading obtained by Temperature Pressure Chart conversion from the suction line temperature to obtain the expansion valve setting (Superheat). Thermo Bulb Suction Line Temperature (F)
-Suction Pressure Temperature Conversion (F) Superheat (F) NOTE: To establish stable condition, run the unit at least 15 minutes at 1000 rpm engine speed so the evaporator air inlet temperature reaches 70.0 to 80.0 (°F) (21.0 to 27.0 C). Read pressure and tempera- ture readings simultaneously. Temperature difference should be 10.0 to 15.0 (°F) (5.5 to 8.0 C). CAUTION - Thermo King expansion valves are Factory preset and do not require adjustment. It is very difficult to establish controlled conditions in the field to accu- rately adjust superheat. If it is verified that the super- heat is out of range and before attempti ng to adjust the expansion valve, the following three causes for an out of range reading MUST be carefully checked. Check the following: 1. Dirty air filters, or other cause of reduced air flow. 2. Sensing bulb leaking, bulb placed improperly (on refrigerant line, or bulb is not properly wrapped with insulating tape. 3. Kinked capillary tube. 40
Service Procedures After these items have been checked and expansion valve adjustment is unable to bring the superheat measurement into range, then replace the expansion valve with factory preset part. Superheat Adjustment 1. Remove the cap over the adjusting stem. 2. To reduce superheat, turn the adjusting stem counterclockwise. 3. Make no more than one 1/4 turn of the stem at one time, and observe the change in superheat closely to prevent overshooting the desired setting. As much as 30 minutes may be required to obtain the new bal- ance after the adjustment has been made. 4. When proper readings have been achieved, pump down the low side into the receiver tank. 5. Remove the pressure gauge from the equalizer line and thermometer. 6. Install the equalizer line, open the receiver tank and check for leaks.
66#
52°
Example: R-22 Refrigerant To the suction pressure of 66PSIG (at compressor) Add estimated suction line loss 2 PSI To obtain suction pressure....68 PSIG converted to Temp (at Bulb) AJA823 Your Superheat is
52° 40° 12°
WHAT’S YOUR SUPERHEAT?
41
Notes
42
Leak Testing/Soldering/Clean-Up Refrigerant Leak Check Tools and Recommended Testing Procedures Units low on refrigerant must be tested for leaks and the leaks must be repaired before adding refrigerant. Following are recommended tools and testing procedures:
AC & DC Powered Electronic Detectors DC detectors normally use a heated tip and convectional currents to pull air samples across the sensor. Pum ps used are usually low capacity. Travel Rate 1/2 inch per second. Sensitivity As little as 1/2 oz. refrigerant loss per year.
AC powered electronic detectors normally react faster and are the most reliable. A built-in pump pulls air across the sensor. Travel Rate 1/2 to 1 inch per second. Sensitivity 1 /10 oz. refrigerant loss per year or less.
Liquid Leak Check Solutions Leak check solutions are generally acceptable in areas that are easily reached or where the air is saturated with refrigerant. However, several factors determine how well a solution will work. A good solution should: •
Be bubble free
•
Have a high surface tension
•
Adhere to and not break away from the joint
•
Work for several minutes without evaporating
•
Be commercially made for leak detection
43
Leak Testing/Soldering/Clean-Up Leak Characteristics Multiple leaks may exist. Leak check beyond the first leak. Component or line temperature may determine leak or leak size. Leak test before and after running the unit. Circulating refrigerant oil may temporarily plug leaks on a unit that is operated. When possible, leak check before running the unit.
Leak Testing Recommendations Observe lines and components for an oil and dirt accumulation indicating leak location. Apply liquid bubble solution with soft brush to prevent bubbles from forming. Allow several minutes to work, Blow out confined areas with compressed air to remove refrigerant accumulations. In windy conditions, shield the leak area for leak testing.
Electronic Detectors Calibrate frequently with a standard to be sure of reliability. Calibrate in fresh air to increase sensitivity. Calibrate in slightly contaminated air to reduce sensitivity. Keep sensor free of dirt and refrigerant oil. Move sensor slowly (1/2 inch per second). Start leak testing at the top and work down.
44
Leak Testing/Soldering/Clean-Up Recommended Solders and Soldering Procedures The following solders are recommended when servicing Thermo King refrigeration systems:
Used With R-134a and R-12 Soft Solder
(95/5, 95% tin, 5% antimony) 450° melting point. TK 204-167
Flux Required Identification Uses
Non-corrosive Paste TK 204-417 Smooth, dull silver finish Low pressure, copper to copper lines between the evaporator and the compressor
Used With R-22 and R-407C Silver Solder 15%
(Phoson+) TK 204-634, 1250° melting point.
Flux Suggested
None, may work better with white flux, TK 203-365
Identification
Dark, almost black appearance
Uses
High pressure, copper to copper connections. CANNOT be used with steel
Silver Solder 35%
TK 203-366
Flux Required
TK 203-365, 1350° melting point.
Identification
Bright, smooth, gold finish
Uses
High strength, high pressure connections made of dissimilar metals (brass to copper, copper to steel, etc.)
45
Leak Testing/Soldering/Clean-Up Good soldering connections are frequently the result of extensive practice. However, several factors and techniques if properly observed will help ensure success for even the inexperienced. Tubing Fit Too tight a fit between two pieces of swedged tubing may not permit the solder to flow throughou t the joint. Too loose a fit will also weaken the connection. A five thousandths of an inch space is recommended between two pieces of a swedge joint. This is about equal to two pieces of notebook or typing paper. Cleanliness Remove all grease or oil with solvent or clean rags. Remove oxides from the tubing with scotch brite pads. Sandpaper and steel wool are not recommended as they may contaminate the connection or remove excess metal. Wipe away loose oxide and abrasive particles to prevent contamination. Proper Flux Use recommended fluxes to reduce oxide formation, to aid in cleaning the connection and to help the solder flow. AVOID getting flux inside the tubing. Heat Control Speed is important. Use a neutral flame large enough to finish the job quickly and prevent oxide formation. On swedge connections, heat the male tubing first, then heat the entire connection evenly. Cool slowly. Never cool with water or wet rags.
46
Leak Testing/Soldering/Clean-Up Refrigerant Recovery and Methods of Recovery Whenever refrigerant is removed from a refrigeration unit for service or after leak testing the unit, it must be recovered to limit the potential harm it could cause to the environment if it were allowed to escape to the atmosphere. The following terms are used to refer to the process of removing, storing and cleaning or purifying refrigerant: Recovery . The process of removing refrigerant from a unit and storing it in an external container for later processing. Recycling . The process of removing moisture and/or oil from refrigerant to prepare it for reuse. Reclaiming . The process of cleaning refrigerant to meet the standards of new refrigerant.
47
Leak Testing/Soldering/Clean-Up Recovery from a Working Unit Without An Orit 10 Valve If a unit is operable and the compressor functions, the refrigerant should be removed as a liquid. This is the fastest and most efficient method. Proceed as follows to remove refrigerant as a liquid: 1. Install a gauge manifold on the SSV and the RTOV. 2. If you have an Orit 15 EPR valve. Close the pilot valve hand valve. 3. Attach the service line to the recovery machine inlet. 4. Pump down the unit's low side to force the refrigerant into the condenser and receiver tank. 5. Set the recovery machine for liquid recovery and open high pressure gauge hand valve. Remove the refrigerant through the receiver tank outlet service valve. 6. Recover refrigerant until proper recovery level is achieved.
AJA824 Recovery Unit
48
Leak Testing/Soldering/Clean-Up Recovery from a Working Unit With An Orit 10 Valve If a unit is operable and the compressor functions, the refrigerant should be removed as a liquid. This is the fastest and most efficient method. Proceed as follows to remove refrigerant as a liquid: 1. Install a gauge manifold on the SSV and the RTOV. Install the service line onto the access port on the Orit 10 EPR valve. 2. Open the manifold low side hand valve. 3. Complete a low side pump down. 4. When you have achieved a 20” vacuum, close the low side hand valve on the gauge set. 5. Remove the service hose from the EPR valve and attach to the recovery device. (Note: low loss fittings must be used.) 6. Set the recovery machine for liquid recovery and open high pressure gauge hand valve. Remove the refrigerant through the receiver tank outlet service valve. 7. Recover refrigerant until proper recovery level is achieved.
AJA825
Recovery Unit
Connectservice line to Orit valve during low side pump down only
49
Leak Testing/Soldering/Clean-Up Recovery from a Non-functioning Unit When a unit is inoperable or the compressor will not function, the refrigerant must be removed as a vapor. It can be removed from almost any convenient service port on the compressor or receiver tank. Because refrigerant must evaporate in the unit before removal, it is less efficient and more time consuming than the liquid removal process. 1. On units equipped with an Orit 15 valve or no EPR valve, attach gauge manifold hoses to the SSV and DSV. If equipped with an Orit 10 valve, attach the manifold hoses to the discharge valve and to the access valve on the Orit 10 EPR valve. 2. Open both manifold hand valves. 3. Recover vapor refrigerant until proper EPA recovery levels have been achieved.
Recovery Unit
AJA826
50
Leak Testing/Soldering/Clean-Up System Evacuation and Clean-up Refrigeration systems that have had service performed with the system open to the atmosphere must be evacuated to remove air and moisture that may have entered during service. In addition, systems that have been open to the atmosphere for an extended period may require multiple evacuations to be sure all air and moisture are removed. Refrigeration systems that have had major service or repairs, and systems suspected of having air, moisture, or foreign particle contamination, must follow procedures outlined in TK 40229, "Clean-up of Refrigeration Systems with Thermo King Compressors," and TK 40612, "Evacuation Station Operation and Field Application” Normal Evacuation Procedure 1. Recover and totally recycle refrigerant making sure contaminates are removed from the refrigerant using a certified reclaiming / recycling machine. 2. Properly install evacuation pump and hoses. Attach one evacuation hose to the receiver tank service valve (high side) and the other hose to the suction side (low side) Try to avoid evacuating from schrader valves. Note: Units with EPR valves must be evacuated from both sides of EPR valve. Refer to Service Bulletin No. 362 dated August, 1989. 3. Properly install micron gauge. 4. Install and tighten stem caps on service valves. 5. Evacuate to 500 microns. Once 500 microns are reached, evacuate for 30 additional minutes.
(continued)
51
Leak Testing/Soldering/Clean-Up 6. 7.
Close off unit from pump, shut pump off. Observe micron gauge. Micron level should not exceed 1500 microns within 5 minutes. Address problem if gauge exceeds 1500 microns and re-evacuate. Use nitrogen to purge system before re-evacuating. Note: Leaks or high levels of moisture are common reasons for a poor evacuation. Also, check evacuation equipment and connections, and make sure schrader valves and service valves are capped. Refer to Service Bulletin No. 392, dated January, 1990. 8. Weigh in unit charge. (Check unit maintenance manual for proper charge). 9. Check operating pressures. Ensure the temperature, pressure relation vs. RPM’s are within specification.Your failure to perform the proper clean-up of the system may effect unit warranty. Multiple Evacuation Perform a multiple evacuation if a system has been open to the atmosphere for an extended period or as recommended in TK 40229 "Clean-up of Refrigeration Systems with Thermo King Compressors". 1. Check the evacuation equipment and repair as required. 2. Open the shut-off valve and place the unit service valves in the mid-seat position. 3. Evacuate the system to 2000 microns for 30 minutes. 4. Break the vacuum with nitrogen until a 2 to 5 lb. positive pressure is established. 5. Allow the nitrogen to remain in the system for 10 minutes or more. 6. Evacuate the refrigeration system to 1500 microns for 30 minutes. 7. Break the vacuum with nitrogen until a 2 to 5 lb. positive pressure is established 8. Change the liquid line drier. 9. Evacuate the system to 500 microns then continue to evacuate for 30 minutes. 10. Close the hand valves on the gauge manifold. 11. Remove the vacuum pump and charge the unit with refrigerant. 12. Prepare the unit for service.
52
Leak Testing/Soldering/Clean-Up Compressor Oil Acid Test (Kit TK 203-346) An acid test of the compressor oil must be done whenever an acid condition is suspected. Perform an acid test whenever a unit has a substantial refrigerant loss, a noisy compressor or dark/dirty oil as noted in TK 40229 "Clean-up of Refrigeration Systems with Thermo King Compressors". To complete an oil acid test: 1. Use an access valve (TK 204-625) on the compressor oil pump service port and draw an oil sample. Note: Two Thermo King acid test kits are available one for alkybenzene (synthetic) compressor oil and one for polyolester compressor oil. Be sure to use the correct test kit. Clear Oil Appearance of good oil. Black Oil
Brown Oil
Carbonization from operating a unit with air and moisture in the system. Results from moisture in the system causing an acid condition and subsequent copper plating.
Gray/Metallic Caused by wear metal from pistons bearings, cylinders, etc. 2. 3. 4.
Add oil to the test bottle up to the line on the neck. Replace the cover and shake. Compare the oil kit color with the color test strip.
53
Leak Testing/Soldering/Clean-Up Compressor Oil Filter Kit (TK 20-123) This oil filter is recommended for permanent installation on units whenever a compressor has been replaced or the system has had foreign particle contamination as defined in TK 40229, "Clean-up of Refrigeration Systems with Thermo King Compressors". The filter cartridge is replaceable after performing a compressor or low side pump down. The filter should be changed annually. Note: Can not be used on 4GB bus compressors.
AJA827
Suction Line Filter The suction line filter is designed for use when major system contamination has occurred as defined in TK 40229, "Clean-up of Refrigeration Systems with Thermo King Compressors". As indicated in the recommended clean-up procedure, the compressor oil filter is also recommended for permanent installation on systems requiring the use of a suction filter.
54
Refrigerant Types and Pressures Refrigerant Types/Properties During unit cooling, refrigerant is the vehicle within the refrigeration system that picks up the heat inside the bus. It then carries the heat outside where it can be given up to the outside air. Following are characteristics of refrigerants and oils presently used in Thermo King units:
Refrigerant Types/Properties R-12
R-22
R-134a
R-407C
Container Color
White
Oil Type
Mineral Base TK 64-426, or Synthetic TK 67-404
Leak Testing
Liquid Bubble Solution or CFC Electronic Detectors
Container Color
Green
Oil Type
Synthetic TK 67-404
Leak Testing
Liquid Bubble Solution and CFC Electronic Detectors
Contai ner Col or
Li ght Bl ue or Brown
Oil Type
Polyolester TK 203-413
Leak Testing
Liquid Bubble Solution or Halogen Electronic Detector
Container Color
Medium Brown
Oil Type
Polyolester TK 203-413
Leak Testing
Liquid Bubble Solution or Halogen Electronic Detector
WARNING: Some autos, trucks and other air condition- ing systems use PAG Polyalkylene Glycol compressor lubricant. DO NOT mix with Thermo King Ester Base Oils. NOTE: Check unit maintenance manual for proper oil to use on ShuttleAire.
55
Temperature Pressure Relationships
56
Temperature Pressure Relationships
57
Notes
58
Glossary Bus Air Conditioning Terminology Absolute Pressure The pressure above a perfect vacuum, expressed in pounds per square inch absolute (psia) or kilopascals (kPa). Ambient Air The air surrounding an object. Ambient Temperature Sensor Measures outside air temperature and selects the temperature where the compressor is disabled. Ambient Temperature Temperature of the air surrounding an object. Atmospheric Pressure The atmosphere surrounding the earth extends many miles above the surface of the earth. The weight of that atmosphere pressing down on the earth is relatively constant except for minor changes due to changing weather conditions. As a basic reference for comparison, the atmospheric pressure at sea level has been universally established at 14.7 psi (100 kPa) and is equivalent to the pressure exerted by a column of mercury 29.92 inches high. At altitudes above sea level, the depth of the atmospheric blanket surrounding the earth is less; therefore, the atmospheric pressure is less. Back Seated Service Valve The valve stem is backed all the way out (counterclockwise). In this position, the valve outlet is open and the service port is closed. Boiling Point The temperature at which a liquid vaporizes upon the addition of heat or by the reduction of pressure. Boost Pump Increases the flow of engine coolant to the heating coil.
59
Glossary Box Temperature A term use in transport refrigeration that refers to the temperature within a bus body. Box temperature is the same as return air temperature. British Thermal Unit (BTU) The amount of heat required to increase the temperature of a pound of water one degree Fahrenheit. Brushless Motor An alternating current (AC) motor having no commutator or brushes. Calorie The amount of heat required to raise temperature of one gram of water one degree Celsius. Capacity Rate of heat transfer measured in tons, BTU’s per hour, K cal per hours, or Watts. Example: The refrigeration capacity with R-22 is 125,000 BTU per hour at 2000 RPM and with R-134a is 100,000 BTU per hour at 2000 RPM Change of State The process of changing from a liquid to a gas, gas to liquid, solid to liquid, or liquid to solid. Charge 1) The amount of refrigerant in a system. 2) The process of adding refrigerant to a system. Check Valve A valve that allows refrigerant to flow in only one direction. Coil Drop The term is often used in reference to the temperature difference of air entering the evaporator coil versus the temperature out. Coil Drop can also be referred to as Temperature Differential (TD). Coil Temperature Sensor Measures coil temperature, usually on the evaporator coil to control freezing.
60
Glossary Compound Gauge A gauge that is calibrated in both pounds and inches to measure pressure and vacuum. This gauge is normally used to measure “low side” pressures. Compressor The refrigeration component that compresses refrigerant vapor and creates refrigerant flow. Compressor Capacity/Efficiency Test A test used to check the condition of compressor piston reeds, piston-to-cylinder wall clearance, piston and cylinder condition, and compressor performance capability. Compressor Pump Down A service procedure used to check for internal leaks through the discharge valve plates, and to perform service work on the compressor. Condenser An arrangement of tubing in which the vaporized and compressed refrigerant is liquefied as heat is removed. Conduction Heat transfer between two substances in physical contact. Convection Heat transfer between substances through the movement of a fluid (gas or liquid). Coolant Valve Controls coolant flow to the heater coil. Cool Mode (Reheat Position) When the unit reaches set point, the clutch remains engaged while the boost pump operates. Cool Mode (Cycling Clutch) When the unit reaches set point, the clutch cycles off. The unit operates in vent. Compressor Discharge Sensor Active above 250°F. Senses temperature of discharge gas leaving the compressor.
61
Glossary Dehydration Process or removing moisture from a refrigeration system or product. A refrigeration system is considered fully dehydrated when it can maintain a 2000 micron vacuum for five minutes or longer. Dehydrator A device used to remove moisture from refrigerant. Drier. Receiver drier. Discharge Pressure Operating pressure measured in the discharge line at the compressor outlet. Discharge Temperature The temperature of refrigerant at the compressor outlet. Distributor A device located between the expansion valve and evaporator coil designed to divide the flow of liquid refrigerant among several parallel paths in the evaporator coil. Drier (See Dehydrator) DSV Discharge Service Valve EPROM Erasable Programmable Read-Only Memory. A programmable software chip that can be erased and reprogrammed. EPR Valve Evaporator Pressure Regulator. Controls evaporator coil temperature to prevent freezing. Evacuation The removal of non-condensable gases from the refrigeration system. Evaporation A change of state from liquid to vapor.
62
Glossary Evaporator The part of the refrigeration system, located in the bus interior, that absorbs heat during the cooling cycle. Expansion Valve A device that meters liquid refrigerant to the distributor and evaporator coil in direct response to heat load on the evaporator. Flash Gas The instantaneous vaporization of refrigerant caused by the reduction of pressure on liquid refrigerant when it passes through a pressure reducing device. Foaming A condition caused by refrigerant boiling out of the compressor oil. Foaming of the compressor oil is often seen through the compressor oil sight glass for several minutes after a unit is started. Fractionation When a refrigerant blend in the vapor form separates into its individual refrigerant components. Freeze Point The temperature at which a liquid makes a physical change to a solid. For water this change occurs at 32°F (O°C). Freeze Thermostat Senses and corrects coil freeze-up. Freeze-Up 1. The formation of ice at the expansion valve. 2. The formation of a solid ice mass over the evaporator coil reducing air flow. Front Seated When the stem of a service valve is turned in (fully clockwise) to stop refrigerant flow through the valve. The service port is open when the valve is front seated.
63
Glossary Frosting Back 1. The condition of frost formation on the suction line during the cooling cycle. This happens when the suction line temperature is below the dew point. 2. The formation of frost on the suction line, or any portion of the compressor during the cooling or heating cycle indicating liquid refrigerant is vaporizing at these locations. Gas Common terminology for refrigerant in the gaseous state. See Vapor. Gauge Pressure The pressure reading measured on a gauge calibrated to read zero psi (zero kPa) at atmospheric pressure. Head Pressure A term commonly used to mean discharge pressure. Heat Heat is a form of energy. Heat is often defined as energy in transfer, for it is never content to stand still, but always moving from a warm body to a colder body. The terms warmer and colder are only comparative. Heat exists at any temperature above absolute zero, even though it may be in extremely small quantities. Heat Exchanger The component in which heat is transferred from one fluid to the other. Normally, it transfers heat from the liquid line to the suction line. Heat Mode The evaporator fan motor runs at selected speed, the boost pump and coolant valve are activated, and the condenser fan motor is stopped. Heat of Compression Heat added to refrigerant gas as a result of the work energy used in compression. Heat Radiation Heat transfer through a substance without changing the substance temperature. 64
Glossary Heat Transfer Heat always travels from a warm object to a colder object. The rate of heat travel is in direct proportion to the temperature difference between the two bodies. Heat can travel in any of three ways: radiation, conduction, or convection. Hertz A unit of electrical frequency equal to one cycle per second. High Pressure Cut Out A pressure-operated switch that opens to stop unit operation when discharge pressure reaches a predetermined maximum. High Pressure Relief Valve A safety valve on the refrigeration system that allows refrigerant to escape from the system if pressures exceed a predetermined value. High Side The portion of the refrigeration system operating under condensing pressure. That portion of a refrigeration system between the compressor output and the expansion valve. Hot Gas Bypass Valve A solenoid valve controlled by a pressure switch used to reduce condenser pressure. Excess condenser pressure is piped to the evaporator inlet. Inches of Vacuum Pressure below atmospheric pressure. Latent Heat The heat added or removed from a substance that accounts for a change in state without any measurable change in temperature. For some substances there are two conditions where latent heat is required to make the change of state. They are - changing from a solid to a liquid called fusion, and from liquid to vapor, or vapor to liquid called vaporization or condensation.
65
Glossary Latent Heat of Evaporation A change of substance from a liquid to a vapor, or from a vapor back to a liquid involves the latent heat of condensation. Since boiling is only a rapid evaporating process, it might also be called the latent heat of boiling, the latent heat of vaporization, or for the reverse process, the latent heat of condensation. When one pound of water boils or evaporates, it absorbs 970 BTU (1023 joules) and to condense one pound of steam to water 970 BTU (1023 joules) must be extracted from it. Latent Heat of Fusion A change of substance from a solid to a liquid, or from a liquid to a solid involves the latent heat of fusion. When one pound of ice melts, it absorbs 144 BTU’s, and if one pound of water is to be frozen into ice, 144 BTU’s must be removed from the water. Latent Heat of Sublimation A change in state directly from a solid to a vapor without going through the liquid phase. The most common example is the use of “dry ice” (solid carbon dioxide) for cooling. The same process can occur with ice below the freezing point, and is also utilized in some freeze-drying processes at extremely low temperatures and high vacuums. The latent heat of sublimation is equal to the sum of the latent heat of fusion and the latent heat of evaporation. LED Light Emitting Diode. A small, neon bulb that operates at low voltage (3 to 4 volts). Liquid Line The tube carrying liquid refrigerant from the receiver tank to the expansion valve. Load 1. The people being cooled and transported. 2. The amount of heat that is being removed by the refrigeration system. 3. The power output of a generator. 4. The resistance of a device to which power is delivered.
66
Glossary Low Pressure Cut Out A pressure-operated switch that opens to stop unit operation when suction pressure reaches a predetermined minimum. Low Side The part of a refrigeration system normally under low pressure during the cool mode. (This includes the liquid line during a low side pump down.) Motor Driver DC to AC inverter used to supply voltage to the brushless AC motor. Perfect Vacuum 29.92” Hg (29.92 inches of mercury) Piston Reeds Ring-shaped reeds (one way valves) located on top of each piston in a reciprocating compressor. As the piston moves down in the cylinder, the reed opens to allow refrigerant gas to move from the crankcase area to the area above the piston. As the piston moves up in the cylinder, the reed closes to trap refrigerant gas above the piston. The compressor capacity test is used to check the condition of piston reeds. Pressure The push exerted against container walls by a liquid or gas, usually measured in pounds per square inch or kilopascals (kPa). Pressure Drop 1. Loss in line pressure from one point to another due to restriction. 2. Loss of pressure due to condensing vapor. 3. Loss of pressure due to a leak in the system. Product The cargo being temperature-controlled. PSIA Pound per square inch - Absolute. See Absolute Pressure.
67
Glossary PSIG Pounds per Square Inch Gauge. Pressure in pounds per square inch as displayed by a gauge calibrated to zero when open to the atmosphere. Pump Down A procedure used to service a refrigeration system. Refrigerant in a charged unit is pumped and stored in one part of the system while servicing another part of the system. Purging Releasing a vapor through a refrigeration system to atmosphere to remove contaminants from the system. The recommended vapor used for purging dry nitrogen. Radiation Radiation is the transfer of heat by waves similar to light waves or radio waves. For example, the sun’s energy is transferred to the earth by radiation. Receiver Tank A refrigerant storage tank. Reclaim The process of cleaning refrigerant to like-new condition. A process normally done by a licensed reclaiming service not an infield practice. Reclaimer A machine used for removing refrigerant from a unit, removing contaminants from the refrigerant, and placing the refrigerant into a storage container. Recover To remove refrigerant from a system and store it in an external container without testing or processing it. Recycle A procedure that removes refrigerant from a unit, cleans the refrigerant through a series of filters, and returns the refrigerant to the unit or a bottle. To clean refrigerant for reuse by removing oil and contaminants through single or multiple passes through moisture absorption devices such as replaceable core filter driers. Considered an infield practice. 68
Glossary Refrigerant The fluid or vehicle used to carry heat from one point to another in the refrigeration system. It picks up heat as it vaporizes and gives up heat as it condenses. Return Air Sensor Measures coach interior air temperature, usually mounted in the return air flow of the evaporator. Return Air Temperature See Box Temperature. RTOV An abbreviation for Receiver Tank Outlet Valve, which is the service valve on the recovery tank. Saturated Vapor The condition when a refrigerant has liquid form present with the vapor. This occurs in the evaporator when refrigerant is making the change from liquid to vapor or in the condenser when the refrigerant is condensing. Saturation Temperature The condition where temperature and pressure allow both liquid and vapor to exist simultaneously. A saturated liquid or vapor is one at its boiling point, and for water at sea level, the saturation temperature is 212 F (I00 C). At higher pressure, the saturation temperature increases, and with a decrease in pressure, the saturation temperature decreases. Sensible Heat The heat required to change temperature of a substance. When the temperature of water is raised from 32 F to 212 F, an increase in sensible heat content is taking place. Set Point The temperature selected on a thermostat or micro controller. This is normally the desired temperature. Short Cycling The circulation of air from the evaporator outlet and back to the evaporator inlet without properly circulating through the load. Short cycling is normally caused by improper ducting practices. This may also refer to improper clutch operation. 69
Glossary Sight Glass A system component that permits visual inspection of oil and/or refrigerant level and condition. Slugging The return of either refrigerant or oil to the compressor in a liquid condition. Slugging can cause knocking and compressor damage. Sometimes called “liquid slugging”. Solenoid Valve An electromagnet valve that can be opened or closed electrically. Specific Gravity Specific gravity (sp.gr.) is a ratio comparing the weight of a substance to the weight of an equal volume of water. Water is considered to have a specific gravity of one. Objects which float on water have a specific gravity of less than one. Objects which sink in water have a specific gravity greater than one. Specific Heat Heat required to change the temperature of a given unit of a substance compared to the amount of heat required to change the temperature of an identical amount of water. It is expressed in BTU’s per pound per degree Fahrenheit or joules per kilogram kelvin. SSV Suction Service Valve. Suction Line A flexible line, to absorb vibration, that carries refrigerant from the evaporator back to the compressor. Suction Reeds See Piston Reeds Superheated Vapor Vapor that has heat added to it after it has changed from a liquid to a vapor without any additional change in pressure.
70
Glossary TD The abbreviation for Temperature Differential or Temperature Difference. The term is often used in reference to the temperature difference of air entering the evaporator coil versus the temperature out. TD can also be referred to as Coil Drop. Temperature Temperature is the word used to describe the intensity of heat. In the United States, temperature is normally measured in degrees Fahrenheit, but the Celsius scale is widely used in other parts of the world. Thermodynamics Thermodynamics is the branch of science that explains the mechanical action of heat. There are several fundamental laws of thermodynamics. The first and most important of these laws is that energy can neither be created nor destroyed, but can be converted from one type to another. Thermostat Controls electrical devices in bus based on temperature. Ton The common unit used to measure refrigeration effect. The amount of heat absorbed by one ton (2000 lb.) of ice as it changes to liquid over a 24-hour period. It is the refrigerating equivalent of 12,000 BTU’s per hour. (One pound of ice absorbs 144 B.t.u. As it melts. One ton of ice absorbs 288,000 B.t.u. When one ton of ice melts in 24 hours, the rate is 288,000 (24 or 12,000 B.t.u. per hour.) Unloader Valve Used on some compressors to limit capacity by either shutting off suction gas or bypassing gas back to the suction side of the compressor. Valve Plate (Discharge Valve Plate) An internal part of the compressor located above each piston. It operates as a check valve, allowing refrigerant gas to leave the area above the piston while preventing its return when the piston is on the down-stroke. The compressor pump down procedure is used to check valve plate condition.
71
Glossary Vapor Common terminology for refrigerant in a gaseous state. See Gas. Vent Mode Coach interior air is recirculated. Volumetric Efficiency The ratio of actual volume of refrigerant gas pumped by the compressor to the volume displaced by the compressor pistons. Watt A term defining the cooling ability of a unit. One Watt = 3.42 BTU
72
