Air Balancing Procedure

STANDARD STANDA RD HVAC TESTING, TESTING, ADJ A DJUSTING, USTING, AND BA B A L A NCING PROCEDURES

Table Of Cont ents

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CONSTANT AIR SYSTEM (DX)

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VARIABLE AIR SYSTEM (DX)

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CONSTANT AIR & HYDRONIC SYSTEM

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VARIABLE AIR & HYDRONIC SYSTEM

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AIR & HYDRONIC SYSTEM (with Cooling Tower)

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SOUND TEST PROCEDURE

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LIST OF INSTRUMENTS

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SAMPLE FORMS

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SYSTEM READY TO BALANCE CHECKLIST

CONSTANT AIR SYSTEM (DX)

HVAC TESTING, ADJUSTING & BALANCING PROCEDURES FOR

AIR SYSTEM

1. INTRODUCTION Test procedures (in compliance with the project Specification) shall be performed in accordance with the latest NATIONAL ENVIRONMENTAL BALANCING BUREAU (NEBB) publication "Procedural Standards for Testing, Adjusting and Balancing of Environmental Systems, 1998". 2. APPLICABLE DOCUMENTS Documentation required prior to on-site testing consist of the technical specifications, record drawings (or asbuilt if available), approved submittal data, and other documents as may be required. 3. PREREQUISITES Prior to the proceeding with the testing activities, the following prerequisites must be completed: 3.1. 3.2. 3.3. 3.4. 3.5. 3.6.

Procedures submitted and approved. Installations are complete. Construction related tests complete (pressure, leakage, etc.) Quality Control inspection is complete. Installation Verification checks successfully completed. Applicable documents prepared and available.

4. INSTRUMENTATION The list of test instruments that will be needed for the testing and balancing of the systems is compiled. Instruments requiring calibration are checked prior to mobilization to ensure that the calibration expiration date has not passed and that the certificates are readily available when reporting to begin actual testing and balancing. Refer to “Attachment A” for the List of Instruments. 5. PROCEDURES These procedures cover the placing of the various HVAC systems into operation, testing, adjusting and balancing fluid flows, and upon completion of the preceding tests, conducting operational tests of the various systems to determine the actual system performances. All other test and reporting as required to confirm that the installation meets the specified conditions shall also be performed. Specific procedures for each activity are provided hereunder. 5.1. PRELIMINARY OFFICE PROCEDURES Testing, adjusting and balancing of HVAC system is accomplished using systematic procedures, the entire TAB process is organized and planned prior to reporting to site to commence actual testing. TAB preparatory work accomplished in the office is to be broken down into three (3) categories: 1. 2. 3.

Procurement of Data. System review and analysis include agenda and preliminary paperwork. Planning and scheduling TAB field procedures.

5.1.1.

Procurement of Data

Standard TAB Procedure - Air System

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Obtain all applicable plans and contract documents including change orders, project specifications, approved shop drawings and equipment submittals. A) Drawings Complete set of up-to-date drawings, including all the latest revisions and addenda will be obtained, including all temperature control system drawings, which indicate the sequence of operation of all HVAC systems. B) Specifications Obtain the relevant technical specifications, in order to identify the precise data and tests which are required and what guidelines or balancing procedures are desired. All addenda and revisions must be included. C) Submittal Data Obtain all applicable approved submittals for all items of HVAC equipment including, where necessary, all manufacturers’ performance criteria, operating curves, etc. 5.1.2.

Review and Analysis of the Systems

After all preliminary data has been collected, a study of each HVAC system is performed to identify any discrepancies in the data or drawings that may prevent the proper balancing and performance of the system, and to develop an agenda to establish the best approach for testing and balancing. A) System Components and Types A review of plans, specifications and equipment data is performed for each system, noting such things as type and location of the areas served, types of systems, etc. Each system is identified i.e. whether primary and secondary systems are interconnected or interlocked with other systems. Location of motor control centers, breakers, etc. are also identified and noted. Equipment schedules, temperature control drawings and sequence of operation of control for each system is particularly reviewed in detail. B) Schematic Diagrams A schematic layout of duct system is prepared indicating all components that pertain to balancing of the system (e.g. balancing dampers, air terminals, etc.) All air terminals are identified with an appropriate numbering system that will be easily recognized and understood by both field personnel and the person who will ultimately review the report. C) Processing the Report Forms All the design data available from the approved drawings and submittals is entered on the relevant Test Report upon completion of the schematic diagrams and preliminary paperwork. Refer to “Attachment B” for sample of test report forms. D) Agenda


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An agenda is prepared, which includes a preliminary report identifying any discrepancies that would prevent the proper testing and balancing of the systems, a description of each system and its operation, and all proposed balancing procedures. (1) Balancing Devices A review of the project drawings, schematics and details is made to insure all necessary balancing dampers are provided to facilitate the balancing work. (2) System Capacity Review A check of the total flow requirements of all system terminal units in comparison to the fan capacities is performed to insure compatibility of the equipment and system. A review of the project drawings, schematics and details is made to insure all necessary balancing devices are provided to facilitate the balancing work. (3) Location of Flow Measuring Devices Desired location for the measurement of airflow quantities are identified, and provisions of flow measurement devices are confirmed if applicable. (4) Sequence of Operation Temperature control system diagrams are examined to determine the method to be used to set the HVAC system components (ATC dampers, etc.) and the mode of operation in which the system should be placed for testing and balancing. (5) Proposed Balancing Procedure After identification of the type of system, the balancing procedure to be used is decided. Every system is slightly different and some modification may be necessary to the standard procedure to permit accurate testing and balancing in some situations. 5.1.3.

Planning TAB Field Procedures

A schedule and plan for the testing and balancing is prepared in accordance with the main program to permit manpower allocations to be made. This plan shall be agreed to with all parties involved with the testing and balancing prior to start of test. 5.2. PRELIMINARY FIELD PROCEDURES 5.2.1.

Readiness Check

When all preliminary TAB work in the office has been completed, a site inspection will be performed upon mobilization. Any deficiencies that will cause delays will be promptly reported to the proper authority, in writing. A preliminary systems check will be conducted by the HVAC Contractor to verify that the building and its system are ready for TAB work, prior to mobilization. Forms are provided as “Attachment C” to these procedures. The steps listed below shall be systematically followed to determine the status of each system. The Installing Contractor is responsible for setting the equipment into proper operation. 5.2.2.

Air System Inspections


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A) Air Handling Units/ Built-up Units 1.

FANS

a)

Electric starter, disconnect switches and main circuit breakers will be located and identified. Any interlocked equipment and circuit interrupting equipment such as freezestats and firestats, shall also be identified. Thermal and electrical overload devices such as fuses and heater coils will be checked to ensure they are of the correct size for the equipment load.

b)

The availability of the electrical power available for start-up and testing shall be determined and that the voltage and equipment needs are compatible. Before touching any equipment, it will be determined that it is safely locked out while being checked. The electrical disconnect switch for the fan will be OFF and tagged or locked.

c)

The inside of the fan and associated ductwork, where possible, shall be inspected for any debris that might get into the fan and cause damage when the fan is started.

d)

The alignment of the drives in belt driven equipment is checked, using a good straightedge or a string line. If the fan and the motor shafts are not parallel, the motor will be repositioned and the belts adjusted to the proper tension.

e)

The fan wheel shall be inspected for the proper alignment and clearance in the housing. If it is not in alignment, fan performance will be affected. Investigation shall also be made for any foreign items on the wheel such as plaster, mud, sealer, etc. These items can cause unbalance and vibration.

f)

All setscrews on the wheel, drives and bearings shall be checked to ensure they are tight.

g)

All mounting bolts shall be checked for tightness on the fans, motors, bearings, belt guards (if applicable), duct connections, etc.

h)

Lubrication of fan and motor shall be verified.

i)

The fan impellers shall be hand-turned and checked for any rubbing of the wheel or the drives.

j)

If vibration isolators or bases are used, these shall be checked for proper adjustment, collapsed spring coils, etc. and that the equipment is leveled. If there are any abnormalities, it shall be verified that the correct isolators have been furnished and are installed in the right locations.

k)

The alignment and tightness of the flexible connections with the ducting shall be checked. If they are stretched tight, they may be damaged when the fan is started and should be replaced with connections with sufficient flexibility.

l)

The motor shall be "bumped” to determine the rotation direction. This is done jointly with the electrician. If the rotation is incorrect, it will need to be reversed before proceeding. (Note that many fans will continue to move air even when running backwards. Therefore, rotation must be visibly checked.) Rotation arrows ar e furnished on many fans.

2.

FILTERS

a)

The correct size and type of filters shall be checked, and it shall be ensured that the correct filters for the system operation are installed. (Sometimes different filters are used temporarily during start-up and construction).


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b)

If the permanent filters are to be used, it shall be confirmed that they are the correct size and type of filter by comparing them with the submitted data and the TAB Test Report Form.

c)

The filters shall be checked for cleanliness. If they are dirty, they will be replaced before starting the TAB work.

d)

It shall be confirmed that the filters and the filter frames are properly installed and are airtight. Any leaks will be corrected.

e)

If the unit has been running with no filters or very dirty filters, all coils downstream of the filters shall be checked for dirt or blockage of air passage. Note: Running unit without filters is not recommended.

3.

DAMPERS All unit and related dampers and their sequence of operation including fire and smoke dampers, shall be checked. Proper damper position during start-up and TAB work is very critical. If dampers are closed, restricting the airflow, serious damage can be done to casing, housing and ductwork. This work will be done in conjunction with a temperature control technician during start-up to insure that the ATC dampers are positioned properly.

4.

COILS

a)

The coils will be checked for cleanliness and straightness of the fins.

b)

All piping connections shall be inspected and confirmed as correct.

c)

It shall be confirmed that the condensate drains from the cooling coil drain pans have been provided and that they are properly trapped and functioning. Improper drain traps are a common cause of leakage, flooding and moisture carry-over.

5.

UNIT CASING The entire unit and the internal components shall be checked for proper air sealing. Leaks will cause whistling, possible moisture carry-over and short-circuiting of the air. Checks shall be particularly made around the pipes and panel holes. Any leaks shall be sealed prior to commencement of testing and balancing.

B) Duct System a)

The system shall be inspected from the fan on out to the last terminal. The following checks shall be made: 1. 2. 3. 4. 5.

b)

The ductwork is complete and installed correctly, and that there are no openings in the ductwork or end caps missing. All access doors shall be closed and secure tight. All air terminals, reheat coils, etc. are installed. The installation matches the plan. All necessary architectural items are installed, such as doors, partitions, ceiling and ceiling plenums, etc. The system is in fact fully ready for balancing.

It shall be confirmed that adequate balancing dampers have been provided and that all volume dampers are installed at the correct location. It shall also be verified that they are wide open and that adequate access has been provided.


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c)

It shall be verified that all terminal devices are installed and that their dampers are open. Verify that the terminals are of the same size and type as specified.

d)

The system shall be checked for leakage. Specially check access doors and hardwares, coils, duct connection, flexible duct and terminal connections. It shall be confirmed that any specified sealing has been done correctly.

e)

It shall be confirmed that any openings between partitions, etc. have been installed and are open to insure proper air passage.

C) Refrigeration Equipment a)

The nameplate data shall be compared with the manufacturer's submittal data and design requirements. Any discrepancies shall be noted.

b)

It shall be verified that the equipment has been started and tested for proper and safe operation in accordance with the manufacturer's recommendations.

c)

It shall be confirmed that the setting of all operational and safety controls for both temperature and pressure are correct.

d)

It shall be confirmed that the provisions are available for the required temperature and pressure measurements.

e)

It shall be confirmed that all compressor crankcase heaters are in operation. Refrigeration equipment should not be started until crankcase heaters have been in operation at least 24 hours. Larger system may require more time, manufacturer's data should be checked for recommended heater operation prior to refrigeration start-up.

5.3. SAFETY TAGGING Before touching any equipment, it will be determined that it is safely locked out while being checked. The electrical disconnect switch will be OFF and tagged or locked. 5.4. TEST, ADJUST AND BALANCE PROCEDURES 5.4.1. 1.

Constant Air Volume System Preparation Upon completion by the Installing Contractor of the inspection procedures detailed previously, the actual TAB work in the field may proceed.

2.

a)

All previously prepared paperwork, drawings, etc. for the system that you are starting on will be assembled.

b)

It will be verified that all preliminary procedures have been performed.

c)

If the initial start-up on the equipment is to be performed, the temperature control technician and an electrician should work with the test engineer if possible, particularly on the larger and more complex systems.

Fan Startup a)

Fan rotation shall be verified by "bumping" the motor i.e. the motor is energized for a fraction of a second and the fan shaft is observed to determine rotation direction. If the


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rotation is incorrect, it will be noted and the electrician responsible for the HVAC equipment shall be advised to correct the fault. The electrician to eliminate the possibility of the TAB technician being held responsible for any possible damage to the motor or equipment will do this.

3.

b)

If the fan rotation is correct, the fan will be started. On larger built-up systems, an observer shall watch for any possible mishaps such as throwing off belts, excessive fan movement, duct bulging and any unusual noises indicating possible mechanical problems. Immediately if it becomes apparent that there is a fault in the operation of the fan it shall be switched off.

c)

After the fan is started, amperage and voltage of the motor will be measured. Voltage should be within 10 percent of the motor nameplate rating, and there should be a very little difference in voltage and amperage between each leg on three phase motors. Amperage should not exceed the nameplate ratings. If the amperage is high, the fan will be stopped immediately.

d)

If everything is operating correctly, any associated equipment related to or interlocked with this unit shall be started so that the complete system is in operation and ready to balance.

e)

Each automatic damper will be inspected to confirm that the damper is being controlled automatically and is in the correct position.

Fan Tests The following tests shall apply to all fans: a)

Amperage The amperage shall be measured using a clamp-on ammeter. Readings shall be taken at the motor junction box for greater accuracy. Any deviation from specified amperage shall be noted and if more than motor full load, then the fan shall be stopped and tests suspended until the cause of the problem is identified and necessary remedial work is completed to ensure proper operation. Motor "no-load" amps may also be measured if necessary. "No-load" conditions shall be achieved by removing the fan belts and running the motor disconnected from the fan pulley. Care shall be taken when removing and replacing the belts to ensure that no damage occurs.

b) Fan and Motor Speed Fan and motor speed shall be measured using a direct contact tachometer, either digital or mechanical. If a direct contact tachometer cannot be used, then an electronic photo-tachometer shall be used. The fan rpm shall also be checked mathematically by using the following equation: Fan rpm = motor rpm x motor pulley pitch diameter Fan pulley pitch diameter For most of the fans, this will not be necessary. However in some instances, calculation may be the only method available to obtain the fan rpm. c)

Static Pressure (SP)


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Static and total pressure readings shall be taken at the fan discharge and inlet. This will be done next to the flexible connections, however, should the readings obtained be obviously inaccurate due to the turbulence at these locations, additional readings shall also be taken further downstream, preferably in a section of straight ductwork. d)

Airflow Total airflow of the fan shall be measured where practical by a pitot tube traverse of the main duct of the system being tested. The accuracy of the pitot tube traverse will be determined by the availability of a satisfactory location to perform the traverse. Reasonably, uniform airflow through the duct is necessary to obtain accurate measurement. Readings shall be taken in all instances in a location as far as possible from any elbows, transitions, dampers, heaters, etc. to reduce the possibility of excessive turbulence marring the test readings. When the readings are not steady and uniform, they will be used in conjunction with the other test data to make a determination of actual airflow. The fan curve and the fan speed data, when used with the calculated brake horsepower can also be used to confirm field readings. It should be noted that static pressure will be the least accurate field readings, depending on how and where they are taken. Nevertheless, with the combination the above reading, it will be possible to make a reasonable determination of the performance of the fan.

e)

Outside Air Most system is designed to operate with the minimum amount of outside air whenever the building is occupied. The procedure for setting the outside air quantities will depend on the system and damper scheme. Where separate minimum and maximum outside air dampers are provided, system shall be started with minimum O.A. dampers and return air (R.A.) dampers open. The maximum O.A. dampers and exhaust air (E.A.) dampers shall be closed. The airflow adjustment will be made by fan speed changes or minimum O.A. damper adjustment. Most systems use just one O.A. damper in conjunction with a minimum position controller, which will open the O.A. and E.A. dampers while closing the R.A. damper. Adjustment will be made at the controller. The temperature control technician will assist if possible during all setting of these dampers. The quantities of O.A. shall be tested making a traverse of the O.A. duct where possible. Otherwise, the amount of O.A. will be calculated by subtracting the actual return air cfm from the actual supply air cfm. If either actual cfm test is not possible, the temperature method shall be used by taking the O.A., R.A. and mixed air temperatures and use the following formula: Tm = XoTo + XrTr 100 Where:

f)

Tm = Temperature of mixed air (ºF) Xo = Percentage of outside air To = Temperature of outside air (ºF) Xr = Percentage of return air Tr = Temperature of return air (ºF)

System Deficiencies If the fan airflow is not within 10% of design requirements, an investigation to try to find the reason for deviation shall be made. The pressure drop across the duct system components (such as coils, filters, etc.) shall be measured and checked against the


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manufacturer's ratings. Duct system noted and compared with the contract drawings. If any radical changes were made to duct system layout during installation which are detrimental to the operation of the system, and corrections are needed, these will be reported to the appropriate persons. If there are no obvious deficiencies, and the airflow is high, the fan will be slowed down by adjusting the drives or making any necessary drive changes. If the airflow is low, the fan speed will be increased. Before doing this, it will be determined if there is adequate motor horsepower available. The new airflow-horsepower relationship will be determined by the used of the fan laws. If any sizable upward change is to be made, the fan manufacturer's data will be checked for the maximum allowable rpm for the fan and its bearings. If the horsepower and static pressure are available and the fan speed can be increased, then the adjustment of the drives to obtain the desired cfm shall be made. g)

Data Entry Once all the fans in the HVAC system and related systems are operating and set up to the design airflow, all data recorded should be entered on the NEB B Test Report Forms.

4.

Pitot Tube Traverses To determine the airflow in every major branch duct, a pitot tube traverse shall be taken in the same manner as the main duct traverse. The locations of the required traverses will be determined and properly recorded in the drawings when the initial paperwork is set up in the office. The necessary design airflow data will then be ready on the appropriate NEBB Test Report Forms. The static pressure at each pitot tube traverse shall be measured and recorded for future use in setting major branch dampers and for possible trouble shooting.

5.

Air Terminal Balancing The previous fan tests are made to determine that the system has the proper airflow and pressure available to continue with the system balancing and that all HVAC units and fans are operating properly. Balancing of the duct systems consist of measuring and adjusting the airflow to the desired rate of each terminal device. The process will require adjustment of the volume dampers and the possible readjustment of the fan speeds. Air terminals shall be measured using either a direct reading hood, or a rotating vane anemometer. If the rotating vane anemometer is utilized the manufacturer's published Ak factors shall be used to determine the air volume from the measured velocity. Any face dampers that are furnished as part of the terminals (diffusers, registers, etc.) will only be used for minor "fine tuning" of the systems. The balancing dampers in the ductwork, where provided, shall be used for all balancing. Using the t erminal dampers can result in excess noise as the damper is closed down. The following procedure will allow the balancing of the air terminals: a)

The necessary design information shall be recorded on the NEBB Test Report Forms with all terminals located and numbered. The size and type of terminal will be verified to ensure that the installed terminal is what was specified. If not, the Ak factor will be different. Unless the direct reading hood is being used, it will be necessary to make absolutely sure that the manufacturer's published Ak and measurement procedures are being used. A direct reading hood will eliminate the need for Ak factors, and special procedures.


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b)

Preliminary measurements shall be taken at every terminal and after measuring and recording all the terminals, the total of the readings, on a zone by zone basis, shall be calculated. A comparison of the terminal totals against the comparable zones duct traverse duct readings, and the required design cfm shall be made. If the readings indicate a system loss of more than 10%, it may not be possible to balance the system properly. If this is the case, an investigation of the duct joints and connections will be made to identify any air leakage. In particular the terminal connections and the plenums for the linear diffusers will be checked. Also a recheck for open access doors, holes in the ducts, etc. shall be conducted and the contractor notified to have the leaks corrected. Attempting to balance the system with leaks will results in wasted time and unsatisfactory results. When it is determine that sufficient air is available in the system and at the terminals, the TAB work shall proceed.

c)

Since the air will go first to the points of least resistance, it will be found that the terminal closest to the fan are high on airflow, and that those near the end of the line are low on the airflow. The result of the preliminary readings will tell exactly what the system is doing and where the air is going. A review of the readings to determine and select terminals that are high on cfm will be made. Closing their branch dampers shall reduce any that are excessively high. On the first "adjusting pass” through the system, the highest terminals shall be throttled to about 10% under design cfm. This will allow for the possible build-up in the other terminals as adjustments are made. After reducing the high airflow terminals, another pass through the entire zone or system shall be made. Each terminal shall be adjusted to the specified airflow when sufficient air is available. After two adjusting passes, most system should be in good balance. An additional pass may be necessary to "trim" the system.

d)

The final pass shall be readings only, with no adjustments, and these readings will be recorded in the final column of the NEBB Air Outlet Test Report. If, during the balancing process, the balancing results in an increase in the system static pressure to the extent that the airflow is reduced to where it is more than 10% below design, it will be necessary to speed up the fan to overcome this loss in cfm. If properly executed balancing results in noisy or other unsatisfactory conditions, the TAB technician shall notify the proper people. If additional dampers are needed, and it is not too late to install them, then the quantity and location of any such dampers shall be recommended. If after notification, no satisfactory response is obtained, the problem shall be noted on the Test Report Forms.

6.

Final Tests: After all balancing adjustments have been completed, final reading shall be taken. This will include a retest of amperage, voltage, static pressure, and rpm of the supply air fan. Final terminal readings will already have been taken. These results will be submitted and shall represent the exact condition of the system when the TAB technician completed the job. The system will be considered balanced when the airflow of each terminal is plus or minus 10% of the design airflow, unless there are conditions beyond control of the TAB firm. All deficiencies shall be outlined on the report. At this point, all the dampers shall be marked for ease of resetting in the event of tampering. Operation of automatic controls shall be checked and verified.


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If there are any obvious air drafts or complaints of it exist, the deflectors or diffuser cones, as provided, shall be adjusted to eliminate any non-uniform room conditions. Specified air patterns from all terminals shall be preferred. 5.5. PERFORMANCE TESTS After the aforementioned air system balancing is complete, all temperatures shall be measured and recorded on the relevant NEBB T est Report Forms. Temperatures to be recorded include the following: a) Air temperature entering and leaving all cooling coils. b) Ambient air temperature, dry bulb and wet bulb. c) Return air temperature, dry bulb and wet bulb.

6. FINAL TEST, INSPECTION AND ACCEPTANCE All final tests and inspection required for acceptance of the aforementioned work shall be done and rechecked in the presence of the Client's representative at random selections of data recorded on the reports.

7. CERTIFIED REPORTS Upon completion of the aforementioned tests, three (3) copies of the certified reports will be submitted to the client after the final tests and inspection. All reports shall contain all relevant data obtained during the testing of the systems. The report will conspicuously identify items not conforming from contract requirements, and obvious maloperation and/or design. This will be noted on the Tests Report if after notifications, no satisfactory response is obtained.


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Air Balancing Procedure

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