MOS, Biện pháp TC, Biện pháp kiểm tra và chạy thử, Method of Statement of Testing and Commissioning in building, Cách kiểm tra và chạy thử các hệ thống trong tòa nhà cao tầng, văn phòng cao ốc, nhà máy, trung tâm thương mại
1 GENERAL MOS TESTING COMMISSIONING System FOR shall be properly tested commissioned to ensure that all the equipment are supplying the designed capacity and installed that air and water flow rates are balanced in accordance with the design CONTENTS: OBJECTIVES 1.According General to the clauses of section 23 (system testing, balancing and in technical specifications for MVAC system Testing and 2.commissioning) Objectives balancing (TAB) to be set to work 3 Preliminary field TAB procedures 3.1 Air system TABTAB procedures PRELIMINARY FIELD PROCEDURES After Process initial installing and checking for assuming 3.2 Exhaust Air Systems statics factory the design systematically follow the steps to be listed as bellow: 3.3 Hydronic system TAB procedures (3.3) air system TAB procedures 3.1 3.4 AIR Specific SYSTEM TAB PROCEDURES 3.5 Refer the clauses 23.2.7 of electrical test in technical specification MVAC system 3.1.1.System Startup TAB 4.Fan Check instruments 5.After TAB report form verifying all control dampers are open, start all relate systems, returns, fans and take preliminary fan static pressure readings 6.and exhaust Appendix Damper Check Be sure automatic damper is being controlled automatically and is in the correct position There will be some effect on the airflow if these dampers are hunting This is undesirable while doing if these dampers are hunting This is undesirable while doing air balancing Therefore, the dampers or their control should be blocked out to keep them in the desired position All dampers should be set for a full flow cooling condition Flow/ Pressure Check Confirm that all related system fans serving each area within the space being balanced are operating If they are not, pressure differences and infiltration or ex-filtration may adversely influence the balancing Positive and negative pressure zones should be identified at this time Damper Setting If a supply fan is connected to a return air system and an outside air intake, set all system dampers and controls so that the air returned from the individual rooms or areas supplied by the fan is returned via the related return air system Page Normally this will involve opening and outside air damper to the minimum position, opening the return air damper, and closing exhaust air and relief air dampers (If the supply system is associated with a run air system and/ or an independent exhaust system, make sure all systems are operating and all related dampers are set properly for the TAB work.) 3.1.2.Fan Testing Perform the following tests adjustments prior to beginning the air balancing - Record nameplate data on fan, motor sheave indicating number and size of belts along with center to center distances Test and record actual operating fan rpm Measure and record actual running amperage Fan Volume Determine the volume of air being moved by the supply fan at design rpm by one or more of the acceptable methods, such as: a Pilot tube traverse of the main duct or the ducts leaving fan discharge, if good location available b Velocity readings across coils, filters, and/ or dampers on the intake side of the fan c Where impossible to take good Pitot tube traverses of duct system, use total sum of terminal device air volume readings d Fan curves or fan performance charts In order to determine fan performance using a fan curve or performance rating chart, it is necessary to take amperage and voltage readings In addition, a static pressure reading across the fan must be recorded With rpm, brake power and static pressure, the fan manufacturer’s data sheets may be used to determine the airflow predicted by the manufacturer Fan performance can deviate from the fan curves, if system effect or other system installation defects are present Fan Adjustment If there are no obvious deficiencies and the airflow is high, the fan can be slowed by adjusting the drives or making drive changes When the airflow is low, the fan speed should be increased First determine if there is adequate fan motor capacity available The new airflow-fan power relationship can be determined by use of the fan laws Fan Drive Changes When new HAVC systems not perform as designed, new drives and motor are often required The financial responsibility for these items not belong to Page the TAB technician, but the balancing readings will have a lot to with determining responsibility Be sure included the necessary data together with explanations about how and where the readings were taken The above steps should also be used for any return air or exhaust air fan associated with the HVAC system in question Fan Amperage Always recheck the amperage whenever any rpm change or major damper setting change is made Fan Static Pressures Subsequent to the adjustments of the fan and obtaining the desired air flow, static pressure readings should be taken at the fan suction and fan discharge to obtain the current total static pressure reading This data along with the actual running amperage should be recorded Many fan rooms are also return air to outside air plenums When taking readings in these rooms, it will be necessary to reference the manometer or anemometer to the atmosphere This is accomplished by running a length of hose from the opposite port of the instrument to the outside or atmosphere Take advantage of existing possible openings available for static pressure (SP) reading such as access doors, handles, bolt holes … that may be removed to get the SP probe into the air stream If none are available, new ones will have to be drilled Be sure to close or cap them when finished 3.1.3 Deficiency Review If the fan volume is not within specified range of the design capacity, determine the reason by reviewing all system conditions, procedures and record data Check and record the air pressure drop across filters, coils, eliminator, sound traps, etc to see if excessive loss is occurring Particularly study duct and casing conditions at the fan inlet and out let for system effect 3.1.4 Return And Outside Air Settings If the fan system you are adjusting has return and outside components and no dedicated return, exhaust or spill air fan it will be necessary to adjust associate dampers achieve the proper air flow for each With the supply fan being set up to the proper air flow as described above it will be essential to take total air readings for the return, outside air, and spill air process of the system Total air readings may be taken by: Duct traverse readings Compilation of individual air inlet readings Page 3 By mathematical calculation from previously taken readings (supply minus return equal outside air) By temperature calculations involving supply air temperature, return air temperature, mixed air temperature, and outside air temperature If volume dampers are provided for each component of the system they should be used for balancing If dampers are not provided it may be necessary to coordinate with the control contactor to limit the stroke or adjustment of the automatically operated damper Upon completion of the above, it is required to check the supply air reading to see if these adjustments adversely affected the total air of the system If the adjustments were severe enough to cause a considerable change in total air flow, all of the above steps must be repeated until proper supply, return, outside, exhaust, and spill air quantities are achieved After proper air quantities have been achieved in the minimum outside air mode of operation it will be necessary to check the 100% outside air mode of operation The automatic dampers should be indexed to the 100% OA Mode of operation and the operating amperage; static pressure should be checked to see if substantial deviations occur in total performance If air flow is increased adjust the volume damper for the outside air or restrict the operation of the automatically operation damper If the air flow substantially decreased it may be necessary to review the system to determine if the 100% OA Mode of operation is the mode with the highest system pressure drop If this is the case the previous readings will have to be taken over in the reverse order and the AC unit adjusted accordingly In order words, the system would be set up for 100% OA and then checked for minimum OA operation with adjustments being made in the minimum mode 3.1.5 Proportional Balancing (Ratio) Method Farthest Branch Select the supply air duct branch farthest from the fan All terminal units or outlets should be numbered on a schematic drawing Branch Duct Readings Preferable using a direct reading flow hood, record the measured airflow Q m from each of the terminal outlets on the selected branch duct 3.1.6 Percentage Of Design Airflow Page Calculate the percentage (X%) of design airflow Qd for each outlet (Q m/Qd=X %) The outlets are renumbered in their degree of percentage of design from the lowest to the highest as shown in the following example Outlet Design Q4 Meas Qm % No L/s L/s 100 150 75 100 160 80 100 170 85 100 180 90 100 200 100 100 210 105 First Step The branch damper for outlet number 6, the lowest percentage of design, is not adjusted The damper for outlet number 9, the next lowest percentage of design, is adjusted until the airflow volume decreases to about 155cfm (77 L/s) Outlet number airflow volume should then come up to about 155cfm (77 L/s) This should be verified by measurement, and these two outlets (6 and 9) should be in balance Second Step Outlet number 5, which is the next lowest percentage of design, is adjusted down to about 160 cfm (80 L/s) Outlet number and should then come up to near 160 cfm (80 L/s) and number should be measured to verify this Outlet numbers 6, and should all be basically in balance Next Step This procedure is followed, proportionally balancing the next highest percentage of design outlet to the previous one balanced This should bring all outlets balanced earlier into balance with it Second Branch Using Figure 13-5, the three (3) outlets numbered to would be proportional balanced to each other in the same manner The two branches then could be proportional balanced using the same procedures used with the terminals Varying Airflows Page If a branch duct has outlets with varying airflows, the percentage of design is calculated for each and same procedures are used, balancing to the percentage of design airflow for each Completion Upon completion of proportional balancing of all out-lets and branches, recheck the supply air fan capacity to the final Qm/Qd percentage If measured airflow (Qm) is lower than design airflow (Q d), the fan airflow volume must be increased to the design airflow (Qd) and all outlets should increase proportionally to their design airflow (Qd) Continue the TAB work by following steps for the stepwise Method 3.1.7 Fan Adjustment Verify the fan capacity and operating conditions again and make a final adjustment to the fan drive, if necessary 3.1.8 Wet Coil Conditions If the supply system was tested with dry coil surfaces and is designed for dehumidification, the total air quantity should be rechecked under wet coil conditions 3.1.9 Airflow Totals After testing and recording all for the terminal units, total the readings on a zone or branch basis Compare the totals to the comparable zone duct traverse reading and the required airflow The total airflow for the terminal units should be close to the traverse reading for the zone or branch The terminal unit total usually will be a little lower due to allowable duct leakage The accuracy of a good Pitot tube traverse is usually considerably better most terminal readings If significant variations are found between traverse reading and time readings, further investigation of ducts may be required 3.1.10 Exhaust Fans Using the methods outlined above, determine the volume of air being handled by a return air fan If used and/or if a central exhaust fan system is used Also determine the airflow being handled by the exhaust fan If several exhaust fans, such as power roof ventilators are related to a particular supply air system, it Page generally is not necessary to measure the airflow of each such exhaust fan until after the supply air system is balanced 3.1.11 Fan Drive Adjustment If the measured airflow of the supply air fan, central return air fan or central exhaust air fan varies more than the specified design plus allowable leakage adjust the drive of each fan to obtain the approximate required airflow Record the fan suction static pressure fan discharge static pressure, amperage and air volume measurements Confirm that the fan motor is not over loaded 3.1.12 Damper Adjustments After balancing the return air system and the associated supply air system, the return air damper should be closed: the relief air dampers should be 100 percent open and return air fan, if used, static pressure and system airflow should be checked again If it is necessary to increase the system static pressure and thereby reduce the fan airflow, adjust the exhaust the exhaust air damper to a maximum position less than 100 percent open Recheck the supply fan airflow with the outside air damper in the full open position Check-Out procedure The following check-out procedure may be used on systems which were designed to balance without the aid of blast gates It is intended as an initial check on the design computations and contractor’s construction in new system, but it may be used also for existing systems when design calculations are available can be recomputed It does not detect poor choices of design criteria such as low conveying or capture velocities and consequently will not reveal inadequate control due to this type of error Agreement with design within ±10% is considered acceptable a Measure flow in duct on inlet side of fan with a Pilot traverse If flow is too low, proceed to step 1.a; if correct, go to step d Check fan size against plan Check fan speed and direction of rotation against design Check fan inlet and outlet configuration against plan b If a discrepancy is found and corrected, return to step a if not, measure fan inlet and outlet static pressures and compute the fan static pressure, and l/s If Page c d e f agreement is acceptable although at some other operating point than specified, fan is satisfactory and trouble is elsewhere in system Proceed to step c If fan inlet static pressure is greater (more negative) than calculated in design, proceed to step d If fan outlet static pressure is greater (more positive) than design, proceed to step h Measure hood static pressure on each hood and check against design If too high on any hood, proceed to step e, if too low, go to step f If correct, go to step j After all hood construction errors and obstructions have been corrected, if hood static pressures are correct, return to step a; if too low, proceed to step f Measure static pressure at various junctions in ducts and compare with design calculations If too high at a junction, proceed upstream until static pressures are too low and isolate the trouble In an area where losses exceed design: Check angle of entries to junctions against plan Check radius of elbows against plan Check duct diameters against plan Check duct for obstruction g After correcting all construction details which deviate from specifications, return to No.1 h Measure pressure differential across air cleaning device and check against manufacture’s data If loss excessive, make necessary corrections and return to step a If loss is less than anticipated, proceed to step h.1 i If errors are found, correct and return to step a If no errors can be detected, recheck design against plan, recalculate and return to step a with new expected design parameters j Measure control velocities at all hoods where possible If control is inadequate, redesign of modify hood k The above process should be repeated until all defects are corrected and the hood static pressures and control velocities are in reasonable agreement with design The actual hood static pressure should then be recorded for use in periodic system checks A file should be prepared containing the following documents: System plan Design calculation Fan rating table Hood static pressures after check-out Maintenance schedule Hood static pressures measurement log Periodic maintenance log The following equipment will be adequate to perform the tests required for this check-out procedure: Page a b c d e Pitot tubes-various lengths Pressure gages-inclined manometer or Magnehelic Rotational speed measuring device-revolution counter or stroboscope Air velocity meter-low range (Velometer or thermal anemometer) Diameter tape 3.2 PROCESS EXHAUST AIR SYSTEMS Kitchen Exhaust Air System - Test Instruments Kitchen makeup air systems must be in operation when the balancing takes place Sometimes make-up is achieved by means of relief grilles from adjoining areas The thermal anemometer is a good instrument for measuring these low face velocities Some swinging vane anemometers (Velometer) can be used at velocities under 100 fpm (0.5m/s) using the low flow probe A Pitot tube used with a micro-manometer also can be used When making a Pitot tube traverse of the duct from the hood, be sure to correct for air density if elevated temperatures are present or predicted - Ducts Most kitchen hood exhaust ducts are made of heavy gage metal, and are covered with a thick fire resistant insulation A Pitot tube traverse of the duct is the most accurate way to test holes will need to be plugged with moisture tight, fire resistant metal plugs or caps, and often, holes are not allowed Avoid putting holes in the bottom of the duct where moisture or grease can accumulate and/or leak out If possible, put the test holes in the side of a riser Never use plastic or rubber test plugs in a kitchen exhaust duct Also, be aware that even if the correct airflow is obtained by the Pitot tube traverse, the hood face velocity may not be sufficient to satisfy local ordinances In this case speed up the fan if the system designer approves and the fan/drive components can accommodate the increase - Filters Velocity reading across grease filters are not usually reliable Accurate free area correction data is not usually available and it would be influenced by the condition of the filters 3.3 HYDRONIC SYSTEM TAB PROCEDURES Page 3.3.1 Hydronic System Measurement Methods 3.3.1.1 Basic hydronic system procedures Procedures outlined the preparation work that must be done prior to the actual testing, adjusting and balancing of the HVAC systems Confirm that these preliminary procedures have been completed and check list prepared Do not attempt to balance a hydronic system before the installation has been completed and all of the air systems have been balanced - Preliminary The following balancing procedures are basic to all types of hydronic distribution systems - Related Systems Confirm that all necessary electrical systems, temperature control systems, all related hydronic piping circuits, and all related duct systems are functional and the any necessary compensation for seasonal effects have been made - Hydronic Systems Ready Verify that all hydronic systems have been cleaned, flushed, refilled, and vented, as required - Valves set Verify that all manual valves are open, or preset as required and all temperature control (automatic) valves are in normal or desired position - Control Devices Verify that all automatically controlled devices in the piping or duct systems will not adversely affect the balancing procedures - Static Head With the pump(s) off, observe and record system static pressure (head) at the pump(s) 3.3.1.2 System Balancing procedures - System Startup Place the systems into operation, check that all air has been vented from the piping systems and allow flow conditions to stabilize Verify that the system compression tank(s) and automatic water fill valve are operating properly - Pump Amperage Record the operating voltage and amperage of the pump(s) and compare these with nameplate ratings and thermal overload heater ratings Verify the speed of each pump Page 10