1、38.1CHAPTER 38 TESTING, ADJUSTING, AND BALANCINGTerminology . 38.1General Criteria. 38.1Air Volumetric Measurement Methods. 38.2Balancing Procedures for Air Distribution 38.3Variable-Volume Systems . 38.4Principles and Procedures for Balancing Hydronic Systems . 38.6Water-Side Balancing. 38.8Hydroni
2、c Balancing Methods. 38.9Fluid Flow Measurement . 38.12Steam Distribution 38.15Cooling Towers. 38.15Temperature Control Verification. 38.16Field Survey for Energy Audit 38.17Reports . 38.18Testing for Sound and Vibration. 38.18YSTEMS that control the environment in a building changeSwith time and us
3、e, and must be rebalanced accordingly. Thedesigner must consider initial and supplementary testing and balanc-ing requirements for commissioning. Complete and accurate operat-ing and maintenance instructions that include intent of design andhow to test, adjust, and balance the building systems are e
4、ssential.Building operating personnel must be well-trained, or qualified oper-ating service organizations must be employed to ensure optimumcomfort, proper process operations, and economical operation.This chapter does not suggest which groups or individuals shouldperform a complete testing, adjusti
5、ng, and balancing procedure. How-ever, the procedure must produce repeatable results that meet thedesign intent and the owners requirements. Overall, one source mustbe responsible for testing, adjusting, and balancing all systems. Aspart of this responsibility, the testing organization should check
6、allequipment under field conditions to ensure compliance.Testing and balancing should be repeated as systems are reno-vated and changed. Testing boilers and other pressure vessels forcompliance with safety codes is not the primary function of the test-ing and balancing firm; rather, it is to verify
7、and adjust operatingconditions in relation to design conditions for flow, temperature,pressure drop, noise, and vibration. ASHRAE Standard 111 detailsprocedures not covered in this chapter.1. TERMINOLOGYTesting, adjusting, and balancing (TAB) is the process of check-ing and adjusting all environment
8、al systems in a building to producethe design objectives. This process includes (1) balancing air andwater distribution systems, (2) adjusting the total system to providedesign quantities, (3) electrical measurement, (4) establishing quan-titative performance of all equipment, (5) verifying automati
9、c con-trol system operation and sequences of operation, and (6) sound andvibration measurement. These procedures are accomplished bychecking installations for conformity to design, measuring andestablishing the fluid quantities of the system as required to meetdesign specifications, and recording an
10、d reporting the results.The following definitions are used in this chapter. Refer to ASH-RAE Terminology (https:/www.ashrae.org/resources-publications/free-resources/ashrae-terminology) for additional definitions.Test. Determine quantitative performance of equipment.Adjust. Regulate the specified fl
11、uid flow rate and air patterns atterminal equipment (e.g., reduce fan speed, adjust a damper).Balance. Proportion flows in the distribution system (submains,branches, and terminals) according to specified design quantities.Balanced System. A system designed to deliver heat transferrequired for occup
12、ant comfort or process load at design conditions.A minimum heat transfer of 97% should be provided to the space orload served at design flow. The flow required for minimum heattransfer establishes the systems flow tolerance. The fluid distribu-tion system should be designed to allow flow to maintain
13、 therequired tolerance and verify its performance.Procedure. An approach to and execution of a sequence of workoperations to yield repeatable results.Report forms. Test data sheets arranged in logical order for sub-mission and review. They should also form the permanent record tobe used as the basis
14、 for any future TAB work.Terminal. A point where the controlled medium (fluid or energy)enters or leaves the distribution system. In air systems, these may bevariable- or constant-volume boxes, registers, grilles, diffusers, lou-vers, and hoods. In water systems, these may be heat transfer coils,fan
15、-coil units, convectors, or finned-tube radiation or radiant panels.2. GENERAL CRITERIAEffective and efficient TAB requires a systematic, thoroughlyplanned procedure implemented by experienced and qualified staff.All activities, including organization, calibration of instruments, andexecution of the
16、 work, should be scheduled. Air-side work must becoordinated with water-side and control work. Preparation includesplanning and scheduling all procedures, collecting necessary data(including all change orders), reviewing data, studying the system tobe worked on, preparing forms, and making prelimina
17、ry field in-spections.Air leakage in a conduit (duct) system can significantly reduceperformance, so conduits (ducts) must be designed, constructed, andinstalled to minimize and control leakage. During construction, allduct systems should be sealed and tested for air leakage. Water,steam, and pneuma
18、tic piping should be tested for leakage, which canharm people and equipment.Design ConsiderationsTAB begins as design functions, with most of the devicesrequired for adjustments being integral parts of the design and instal-lation. To ensure that proper balance can be achieved, the engineershould sh
19、ow and specify a sufficient number of dampers, valves,flow measuring locations, and flow-balancing devices; these must beproperly located in required straight lengths of pipe or duct for accu-rate measurement. Testing depends on system characteristics andlayout. Interaction between individual termin
20、als varies with pres-sures, flow requirements, and control devices.The design engineer should specify balancing tolerances. Mini-mum flow tolerances are 10% for individual terminals andbranches in noncritical applications and 5% for main air ducts. Forcritical water systems where differential pressu
21、res must be main-tained, tolerances of 5% are suggested. For critical air systems, rec-ommendations are the following:The preparation of this chapter is assigned to TC 7.7, Testing and Balancing.38.2 2015 ASHRAE HandbookHVAC Applications (SI)Positive zones:Supply air 0 to +10%Exhaust and return air
22、0 to 10%Negative zones:Supply air 0 to 10%Exhaust and return air 0 to +10%Balancing Devices. Balancing devices should be used to providemaximum flow-limiting ability without causing excessive noise.Flow reduction should be uniform over the entire duct or pipe. Sin-gle-blade dampers or butterfly bala
23、ncing valves are not good bal-ancing valves because of the uneven flow pattern at high pressuredrops. Pressure drop across equipment is not an accurate flow mea-surement but can be used to determine whether the manufacturerdesign pressure is within specified limits. Liberal use of pressuretaps at cr
24、itical points is recommended.3. AIR VOLUMETRIC MEASUREMENT METHODSGeneralThe pitot-tube traverse is the generally accepted method of mea-suring airflow in ducts; ways to measure airflow at individual ter-minals are described by manufacturers. The primary objective is toestablish repeatable measureme
25、nt procedures that correlate with thepitot-tube traverse.Laboratory tests, data, and techniques prescribed by equipmentand air terminal manufacturers must be reviewed and checked foraccuracy, applicability, and repeatability of results. Conversion fac-tors that correlate field data with laboratory r
26、esults must be devel-oped to predict the equipments actual field performance.Air DevicesAll flow-measuring instruments should be field verified by com-paring to pitot-tube traverses to establish correction and/or densityfactors.Generally, correction factors given by air diffuser manufacturersshould
27、be checked for accuracy by field measurement and bycomparing actual flow measured by pitot-tube traverse to actualmeasured velocity. Air diffuser manufacturers usually base theirvolumetric test measurements on a deflecting vane anemometer.The velocity is multiplied by an empirical effective area to
28、obtainthe air diffusers delivery. Accurate results are obtained by measur-ing at the vena contracta with the probe of the deflecting vane ane-mometer. Methods advocated for measuring airflow of troffer-typeterminals are similar to those for air diffusers. A capture hood is frequently used to measure
29、 device airflows,primarily of diffusers and slots. Loss coefficients should be estab-lished for hood measurements with varying flow and deflection set-tings. If the air does not fill the measurement grid, the readings willrequire a correction factor. Rotating vane anemometers are commonly used to me
30、asure air-flow from sidewall grilles. Effective areas (correction factors)should be established with the face dampers fully open and deflec-tion set uniformly on all grilles. Correction factors are requiredwhen measuring airflow in open ducts i.e., damper openings andfume hoods (Sauer and Howell 199
31、0).Duct FlowThe preferred method of measuring duct volumetric flow is thepitot-tube traverse average. The maximum straight run should beobtained before and after the traverse station. To obtain the bestduct velocity profile, measuring points should be located as shownin Chapter 36 of the 2013 ASHRAE
32、 HandbookFundamentals andASHRAE Standard 111. When using factory-fabricated volume-measuring stations, the measurements should be checked against apitot-tube traverse.Power input to a fans driver should be used as only a guide to indi-cate its delivery; it may also be used to verify performance dete
33、rminedby a reliable method (e.g., pitot-tube traverse of systems main) thatconsiders possible system effects. For some fans, the flow rate is notproportional to the power needed to drive them. In some cases, as withforward-curved-blade fans, the same power is required for two ormore flow rates. The
34、backward-curved-blade centrifugal fan is theonly type with a flow rate that varies directly with power input.If an installation has an inadequate straight length of ductwork orno ductwork to allow a pitot-tube traverse, the procedure from Sauerand Howell (1990) can be followed: a vane anemometer rea
35、ds airvelocities at multiple points across the face of a coil to determine aloss coefficient.Mixture PlenumsApproach conditions are often so unfavorable that the air quan-tities comprising a mixture (e.g., outdoor and return air) cannot bedetermined accurately by volumetric measurements. In such cas
36、es,the mixtures temperature indicates the balance (proportions)between the component airstreams. Temperatures must be mea-sured carefully to account for stratification, and the differencebetween outdoor and return temperatures must be greater than 10 K.The temperature of the mixture can be calculate
37、d as follows:Qttm= Qoto+ Qrtr(1)whereQt= total measured air quantity, %Qo= outdoor air quantity, %Qr= return air quantity, %tm= temperature of outdoor and return mixture, Cto= outdoor temperature, Ctr= return temperature, CPressure MeasurementAir pressures measured include barometric, static, veloci
38、ty, total,and differential. For field evaluation of air-handling performance,pressure should be measured per ASHRAE Standard 111 and ana-lyzed together with manufacturers fan curves and system effect aspredicted by AMCA Standard 210. When measured in the field,pressure readings, air quantity, and po
39、wer input often do not corre-late with manufacturers certified performance curves unless propercorrection is made.Pressure drops through equipment such as coils, dampers, or fil-ters should not be used to measure airflow. Pressure is an acceptablemeans of establishing flow volumes only where it is r
40、equired by, andperformed in accordance with, the manufacturer certifying theequipment.StratificationNormal design minimizes conditions causing air turbulence, toproduce the least friction, resistance, and consequent pressure loss.Under some conditions, however, air turbulence is desirable andnecessa
41、ry. For example, two airstreams of different temperaturescan stratify in smooth, uninterrupted flow conditions. In this situa-tion, design should promote mixing. Return and outdoor airstreamsat the inlet side of the air-handling unit tend to stratify whereenlargement of the inlet plenum or casing si
42、ze decreases air veloc-ity. Without a deliberate effort to mix the two airstreams (e.g., incold climates, placing the outdoor air entry at the top of the plenumand return air at the bottom of the plenum to allow natural mixing),stratification can be carried throughout the system (e.g., filter, coils
43、,eliminators, fans, ducts). Stratification can freeze coils and rupturetubes, and can affect temperature control in plenums, spaces, orboth.Stratification can also be reduced by adding vanes to break upand mix the airstreams. No solution to stratification problems isTesting, Adjusting, and Balancing
44、 38.3guaranteed; each condition must be evaluated by field measure-ments and experimentation.4. BALANCING PROCEDURES FOR AIR DISTRIBUTIONNo one established procedure is applicable to all systems. Thebibliography lists sources of additional information.Instruments for Testing and BalancingThe minimum
45、 instruments necessary for air balance areManometer calibrated in 1 Pa divisionsCombination inclined/vertical manometer (0 to 2.5 kPa)Pitot tubes in various lengths, as requiredTachometer (direct-contact, self-timing) or strobe lightClamp-on ammeter with voltage scales root-mean-square (RMS)typeRota
46、ting vane anemometerDeflecting vane anemometerThermal anemometerCapture hoodDigital thermometers (0.05 K increments as a minimum) andglass stem thermometers (0.05 K graduations minimum)Sound level meter with octave band filter set, calibrator, andmicrophoneVibration analyzer capable of measuring dis
47、placement velocityand accelerationWater flowmeters (0 to 12 kPa and 0 to 100 kPa ranges)Compound gageTest gages (700 kPa and 2000 kPa)Sling psychrometerEtched-stem thermometer (0 to 50C in 0.05 K increments)HygrometersRelative humidity and dew-point instrumentsInstruments must be calibrated periodic
48、ally to verify their accu-racy and repeatability before use in the field.Preliminary Procedure for Air Balancing1. Before balancing, all pressure tests (duct leakage) of duct andpiping systems must be complete and acceptable.2. Obtain as-built design drawings and specifications, andbecome thoroughly
49、 acquainted with the design intent.3. Obtain copies of approved shop drawings of all air-handlingequipment, outlets (supply, return, and exhaust), and tempera-ture control diagrams, including performance curves. Comparedesign requirements with shop drawing capacities.4. Compare design to installed equipment and field installation.5. Walk the system from air-handling equipment to terminal unitsto determine variations of installation from design.6. Check dampers (both volume and fire) for correct and lockedposition and temperature control for completeness of installa-t
