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1、,Unit FifteenCommissioning of Variable Air Volume Systems,What is Commissioning(Cx)?,Definition:“A quality-focused process for enhancing the delivery of a project.The process focuses on verifying and documenting that the facility and all of its systems and assemblies are planned,designed,installed,t
2、ested,operated,and maintained to meet the Owners Project Requirements.”ASHRAE Guideline 0-2005,The Commissioning Process,Commissioning is often performed by an independent third-party engineering company.Operates as an owners representative to insure the installed systems meet the owners requirement
3、s and the plans and specificationsUsually hired by the owner,sometimes by the architect,or general contractor.,Commissioning Person,All participants in the construction project have a commissioning responsibility.Participants include the commissioning authority,owner,design professionals,constructio
4、n manager,general contractor,subcontractors,operation and maintenance manager,suppliers,and equipment manufacturers.,Benefits of Commissioning,Reduced change ordersLess warranty and callbacks for contractorSmoother turnover to maintenanceImproved equipment reliabilityReduced IEQ problems Reduced occ
5、upant complaintsImproved productivityCorrect system operation and installationFacility meets Owners expectation and operational needsReduced utility consumption and operational costs,Commissioning Objectives Ensure the facility meets the owners performance requirements Provide a safe and healthy env
6、ironment Provide optimum energy performance Provide a facility that can be efficiently operated and maintained Provide complete orientation and training to facility staff and occupants Provide improved documentation of system characteristics,Commissioning-What did we use to do and why do we need it?
7、CX of mechanical and electrical systems was done by the installing contractors No standardization,or clear approach Most of the real CX occurred during the warranty period as warranty calls Buildings operated less efficiently First year of occupancy was frustrating for the owner Contractors spent mo
8、re money during the warranty periods Contractors can be rushed without enough time to double-check their work Design Engineers do not have enough budget to oversee the construction in detail Owners have had bad experiences with prolonged project closeout,and see CX as a solution Hold contractors acc
9、ountable for the specifications,Commissioning Scope,Mechanical SystemsAll HVAC equipmentBuilding automation system and hardwired controlsElectrical SystemsSwitchgear,major disconnects,backup generators and UPS(Uninterrupted Power Supply)Fire Safety SystemsSecurity SystemsKitchen equipmentIrrigation
10、systemLaboratory Fume hoods,gas control,Commissioning and Construction Phases,Other Types of Commissioning,Retro-commissioningPerformed to existing buildings that have not previously been commissioned,after they have been occupiedUsually instigated as a result of high energy bills or poor occupant c
11、omfortRecommissioningPerformed 5 to 10 years after a building was previously commissionedSometime used as a form of deferred maintenance,Variable Air Volume(VAV)use of varying airflow to control the condition of air,in contrast to the use of constant flow(often)with varying temperature.VAV system co
12、ntrols temperature in a space by varying the quantity of supply air rather than varying the supply air temperature.A VAV terminal unit at the zone varies the quantity of supply air to the space.The supply air temperature is held relatively constant:while supply air temperature can be moderately rese
13、t depending on the season,it must always be low enough to meet the cooling load in the most demanding zone,and to maintain appropriate humidity.,Why use VAV?,Provides multiple zones of comfortLife cycle cost will be less than other HVAC Systems trying to accomplish similar comfort levelsLoad diversi
14、tySmaller equipment(lower AC unit first cost compared to Constant Volume)Less supply air(less energy consumption)Able to adapt to changes in building use,Why Not?,Higher first cost than comparable single zone Controls,equipment,commissioningIncreased maintenance costMore pieces to look after,Constan
15、t volume-variable temperature system have been dominating the HVAC applications in the past for obvious reasons.The implementation of variable volume control has been done with dampers or other mechanical control methods.The advantages of variable air volume system implemented with variable speed co
16、ntrol are:Fast control to keep the comfort zone limits Low consumption of electrical energy Lower consumption of heating and cooling energy than in constant air volume systems Simpler to keep noise level down,1.Introduction2.Commissioning method statement3.System components 4.Preliminary checks5.Com
17、missioning sequence 6.Setting to work 7.Terminal units 8.Secondary air distribution9.Return air spigots 10.System diversity 11.Fan design performance check 12.System performance checks,Frequently used words and phrases:Variable air volume(VAV)system 变风量系统commissioning 试运行 调试 air volume flow rate 空气体
18、积流量terminal unit 终端设备 flexible duct 柔性风管Pitot tube 毕托管 thermal anemometer 热线风速仪supply fan 送风风机 extract fan 排风机over-pressurization 压力过高 spigot 套管、栓、龙头,1.Variable air volume(VAV)systems are dynamic air distribution systems and,as their name implies,the air volume flow rate is varied according to vario
19、us parameters to achieve the required design conditions.2.The fact that VAV systems are designed to vary system performance imposes a number of specific tasks on the commissioning specialist,which must be carried out in order to achieve satisfactory overall performance.3.Proprietary units may employ
20、 a variety of means of regulating air volume flow rate including motorized dampers,inflating bellows,restricting flexible duct sections or a combination of such devices.,Variable air volume(VAV)systems:变风量系统 dynamic:动态的air volume flow rate:空气体积流率 design conditions:设计条件,impose:施加 带来 commissioning spe
21、cialist:调试人员,proprietary:私人拥有的 inflating bellows:静压箱 常用plenum chamberflexible duct section:柔性风管部件,plenum chamber静压箱acoustic plenum chamber 消声静压箱静压箱是送风系统减少动压、增加静压、稳定气流和减少气流振动的一种必要的配件，它可使送风效果更加理想。静压箱的作用 可以把部分动压变为静压使风吹得更远；可以降低噪音 风量均匀分配 静压箱可用来减少噪声，又可获得均匀的静压出风，减少动压损失。而且还有万能接头的作用。把静压箱很好地应用到通风系统中，可提高通风系统的综
22、合性能。,4.Control sensors may measure air flow by means of pressure differential,Pitot tube,flow grid or thermal anemometer using spot or averaging sensors.5.The guidance is not system-specific,because the detailed tasks associated with one system type may not be the same for another type.6.VAV system
23、technology offers such a wide range of design options and proprietary components that the resulting installations are likely to require different commissioning techniques.,pitot tube:毕托管 flow grid:流动网格thermal anemometer:热线风速仪,option:选择 选项,system-specific:根据系统而特殊或不同的,7.To ensure that the appropriate
24、commissioning procedures are employed,the commissioning specialist should carefully review the recommendations of the equipment suppliers.8.VAV systems typically comprise the following components,some of which may require specialist commissioning by the manufacturer in addition to general commission
25、ing as part of a complete air distribution system9.A particular check should be made to ensure that distribution ductwork internals are clean throughout.If there is any doubt regarding the state of system cleanliness,the commissioning specialist should formally draw attention to this.,review:查阅 复习 e
26、quipment suppliers:设备提供商,how to translate?,internal:内部 draw attention to:对注意,10.With the supply and extract fans operating simultaneously,the running speed should be increased gradually.Motor running current checks should be made at various increments,and the results recorded for each fan,to assess
27、performance and prevent overloading of the motor.11.The fans should then be stopped and made safe so that the cause of the static pressure irregularity can be investigated and rectified by the appropriate personnel before proceeding further.12.during the commissioning of the individual VAV terminals
28、,it may be necessary to further fine-tune the fan speed to compensate for any system pressure variations.,current:电流 increment:增量 overloading:过载,irregularity:无规律(的变化)rectify:修正 调整personnel:人员 proceed:继续进行,terminal:终端 终点 terminal station fine-tune:微调,13.All procedures and techniques to be applied in
29、checking terminal unit volume flow rates should be in accordance with the manufacturers instructions and should be incorporated into the commissioning method statement.14.Verification of these arrangements is necessary,and the number of VAV terminal units to be checked should be defined within the p
30、roject commissioning specification.15.at the outset of the VAV terminal checks,the commissioning specialist should select a number of units with inlet duct configurations suitable for in-duct flow measurements to be taken.,instruction:指示 说明 instruction book specificationincorporate:合并 结合 incorporate
31、d:组成公司的 Inc.DELL Inc.statement:说明 陈述,verification:确认 查证 define:详细说明,outset:开始 inlet duct configuration:风管入口结构in-duct flow:风管入口流动,16.Volume flow rate checks by pitot-static duct traverse should be conducted on these terminals to validate the method of flow rate measurement adopted within the commissi
32、oning method statement,17.With such an arrangement,the commissioning specialist must balance proportionally each of the secondary terminals by the methods detailed in section A3.2 so that they discharge the specified proportion of the volume of air delivered by the VAV terminal,within the specified(
33、or appropriate)tolerances.18.For all the above arrangements,regulation of the return air inlets must be carried out to achieve a proportional balance within the specified tolerance limits.,pitot-static duct traverse:风管横截面布置毕托管conduct:进行,carry out:执行,secondary terminal:二次终端设备 tolerance:公差 允许的误差specif
34、ied:指定的,19.It may be necessary to impose a reduced air flow condition on a number of terminals to achieve the required design diversity.20.Where necessary,guidance should be obtained from the unit supplier or manufacturer and close liaison with the designer is recommended to take account of any part
35、icular arrangements that may be required.21.With the required design system diversity applied,total flow rates should be measured and recorded by pitot traverse.,diversity:差异 多样性,How to translate?,guidance:指导 liaison:联络 联系,22.In conjunction with this,the static pressure at the least favored unit sho
36、uld be monitored and the system operating pressure set to its optimum point,i.e.the lowest system operating pressure that still satisfies the least favored unit.23.With the system in this mode,the pressure drop across each component of the air handling unit should be measured and recorded.24.Indicat
37、ive positioning should be specified by the designer,based on the distribution ductwork system layout and the calculated system resistance characteristics.,the least favored unit:处于最不利条件下的设备,indicative:指示性的 指导性的 layout:规划 布局resistance characteristic:阻力特性,pressure drop:压力降,25.It is,therefore,necessary
38、 to set up the fan performance controls for checking both maximum and minimum volumes,in addition to checking the equivalent performance at other intermediate points.26.The setting of the automatic control system should be finalized by the controls specialist in liaison with the commissioning specia
39、list.27.With the supply and extract fans delivering their design maximum air volumes,adjust the outside air damper until the required design volume flow rate is achieved.With the system in its fully turned down condition,the minimum outside air quantity should be checked to ensure that the correct ratio has been maintained.,equivalent performance：类似的性能 intermediate:中间的,turned down:关小，减弱，降低,finalize:最终确定,
