Manuals / Trane / Household Appliance / Air Conditioner

Trane TRG-TRC014-EN manual Diffusers, Components of a VAV System, period two

Models: TRG-TRC014-EN

1 93

Download 93 pages 18.85 Kb

Page 38

Image 38

period two

Components of a VAV System

notes

Diffusers

flexible duct

sheet metal supply duct

diffuser

primary air	VAV
primary air	terminal unit	Figure 48
	terminal unit

Diffusers

Each VAV terminal unit is commonly connected to a downstream, sheet-metal duct that is then connected to the remotely-located diffusers by flexible ducts. Diffusers distribute the supply air effectively to the conditioned space.

Proper air diffusion is an important comfort consideration, especially in VAV systems. Because VAV systems require the diffuser to provide proper space air mixing over a wide range of airflows, diffusers that are specifically intended for use in VAV applications should be used to prevent cold air “dumping” at low airflow rates.

TRG-TRC014-EN

Page 38

Image 38

Trane TRG-TRC014-EN manual Diffusers, Components of a VAV System, period two

Contents

TRG-TRC014-EN Air Conditioning Clinic VAV SystemsOne of the Systems Series One of the Systems Series VAV SystemsA publication of The Trane Company A Trane Air Conditioning Clinic PrefaceVAV Systems period two Contentsperiod one What Is Variable Air Volume? Components of a VAV SystemTRG-TRC014-EN Constant-Volume Variable-TemperatureSystem What Is Variable Air Volume?What Is Variable Air Volume? period oneWhat Is Variable Air Volume? Constant Volume-FullLoadperiod one period one Constant Volume-PartLoadWhat Is Variable Air Volume? Constant Volume-MultipleSpaces Constant Volume-MultipleSpacesWhat Is Variable Air Volume? period oneperiod one Terminal Reheat SystemWhat Is Variable Air Volume? What Is Variable Air Volume? Variable-Air-VolumeVAV SystemVAV-FullLoad period oneWhat Is Variable Air Volume? Why VAV? Energy SavingsVAV-PartLoad Why VAV?period one Why VAV? ComfortWhat Is Variable Air Volume? quiteperiod one System ComparisonWhat Is Variable Air Volume? What Is Variable Air Volume? VAV Building CharacteristicsVariable Thermal Load Profiles period oneWhat Is Variable Air Volume? Independent Space ControlCommon Return Air Path period oneComponents of a VAV System period twoComponents of a VAV System period twoComponents of a VAV System period twoVAV Terminal Units period two Single Duct, Cooling OnlyComponents of a VAV System Single Duct, Cooling Onlyperiod two Space Heating with a VAV SystemComponents of a VAV System Components of a VAV System VAV Reheatprimary air period twoperiod two Fan-PoweredTerminal UnitsComponents of a VAV System parallelParallel, Fan-Powered Parallel, Fan-Poweredplenum air Components of a VAV Systemperiod two Series, Fan-PoweredComponents of a VAV System Components of a VAV System Parallel Versus Series Fan-PoweredSeries, Fan-Powered period twoperiod two Single-DuctVAV SystemsComponents of a VAV System period two Dual-DuctComponents of a VAV System warm primary air cool primary air supply aircool Variable Air Volume to the Spacewarm Components of a VAV SystemComponents of a VAV System Constant Air Volume to the SpaceSingle-Fan, Dual-DuctVAV System period twoperiod two Two-Fan, Dual-DuctVAV SystemComponents of a VAV System Components of a VAV System VAV Terminal Unit ControlsUpstream Pressure Affects Airflow period twoComponents of a VAV System Pressure-DependentControlPressure-IndependentControl period twoComponents of a VAV System Primary Airflow MeasurementTerminal-UnitControl Technologies period twoperiod two Pneumatic ControlComponents of a VAV System period two Electronic ControlComponents of a VAV System period two Direct Digital Control DDCComponents of a VAV System Direct Digital Control DDC Components of a VAV Systemperiod two Electronic pressure transducer provides pressure-independentcontrolperiod two DiffusersComponents of a VAV System Diffusersperiod two Linear Slot DiffuserComponents of a VAV System Coandaperiod two Ceiling-DiffuserCompatibilityComponents of a VAV System Ceiling-DiffuserCompatibility Components of a VAV Systemperiod two cross Tperiod two Supply Duct SystemComponents of a VAV System Supply Duct Systemperiod two Duct DesignComponents of a VAV System Equal friction methodperiod two Duct Design RecommendationsComponents of a VAV System period three System ConfigurationsSystem Configurations period threeSystem Configurations period threePerimeter Spaces Perimeter Spacesperiod three Baseboard Perimeter HeatingSystem Configurations heat loss 450 Btu/hr/ftperiod three Overhead Supply Perimeter HeatingSystem Configurations VAV Reheat System Configurationsperiod three heat loss 250 Btu/hr/ftSystem Configurations Fan-PoweredVAVDual-DuctVAV period threeSystem Configurations Interior SpacesInterior Spaces, Reheat Required period threeSystem Configurations Small BuildingsChangeover/Bypass VAV System period threeperiod three System-LevelControl ModesSystem Configurations System-LevelControl Modesperiod three Occupied ModeSystem Configurations period three Unoccupied ModeSystem Configurations period three Morning Warm-up/Cool-downModeSystem Configurations Fan Modulation period fourFan Modulation period fourFan Modulation period fourSystem Resistance Curve Fan Modulation Operating PointRiding the Fan Curve period fourperiod four Forward-CurvedCentrifugal FanFan Modulation period four Fan Modulation CurveFan Modulation Fan Modulation CurveFan Modulation Fan Control LoopVAV Fan Modulation period fourFan Modulation Fan Modulation MethodsDischarge Dampers period fourDischarge Dampers Fan Modulationperiod four As the VAV terminal units modulate shut, the system resistance curve shifts upwards. The fan begins to “ride up” the constant-speedperformance curve, from the design operating point A, trying to reach the balance point with this new system resistance curve. As a result, the fan delivers a lower airflow at a higher static pressureperiod four Inlet VanesFan Modulation Inlet Vanesperiod four Fan-SpeedControlFan Modulation Fan-SpeedControlperiod four Variable-PitchBlade ControlFan Modulation Variable-PitchBlade Controlperiod four Fan Modulation ComparisonsFan Modulation Fan Modulation Controlling System Static PressureFan Outlet Static-PressureControl period fourperiod four Supply Duct Static-PressureControlFan Modulation sensor located 2/3 down supply ductperiod four Optimized Static-PressureControlFan Modulation sensor locatedperiod four Part-LoadComparisonFan Modulation period five period fiveApplication Considerations Application ConsiderationsApplication Considerations period fiveSystem-LevelVentilation period five Ventilation ResetApplication Considerations outdoor airflowApplication Considerations Freeze Protection for CoilsMeasures to Prevent Coil Freeze-Up period fiveperiod five Part-LoadSpace Humidity ControlApplication Considerations Part-LoadSpace Humidity Controlperiod five Part-LoadSupply Air TemperingApplication Considerations Application Considerations Building Pressure ControlDirect Pressurization Control period fiveA sensitive static-pressurecontroller directly compares the variations between the space static pressure and the outdoor reference static pressure. The controller modulates the capacity of a central relief fan to maintain a fixed static-pressuredifference, usually a slightly positive building pressure. The space static-pressuresensor is typically located in the lobby or near the main entrance Application Considerationsperiod five Review period sixReview period sixfan-poweredVAV terminal unit period sixReview-PeriodTwo ReviewReview Review-PeriodThreeReview-PeriodFour period sixperiod six Review-PeriodFiveReview System-levelventilationTRG-TRC014-EN Reviewperiod six Questions for Period QuizQuestions for Period Questions for PeriodQuestions for Period 11What method of static-pressurecontrol provides the greatest power- savings potential for a VAV system?Quiz TRG-TRC014-EN Answers Glossary parallel fan-poweredterminal unit A fan-poweredVAV terminal unit GlossaryGlossary supply air Conditioned air delivered to a spaceThe Trane Company An American Standard Company