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Trane TRG-TRC014-EN manual Duct Design Recommendations, Components of a VAV System, period two

Models: TRG-TRC014-EN

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Duct Design Recommendations

period two

Components of a VAV System

notes

Duct Design Recommendations

▲Keep as simple and symmetrical as possible

▲Locate main runs, branch runs, and terminal units above hallways or unoccupied spaces

▲Minimize use of flexible ductwork upstream of terminal units

▲Use duct lining or a duct silencer in first duct section to attenuate supply fan noise

▲Place balancing dampers upstream of diffusers in all noncritical branches

▲Reducing transitions should be several duct diameters upstream of terminal units

Figure 54

Other publications contain more complete details related to duct design, but here are a few general recommendations:

nKeep the duct layout as simple and symmetrical as possible

nPlace main duct runs and, when possible, branch runs and terminal units, above hallways and other “unoccupied” areas to ease installation and maintenance and to help attenuate the sound radiated to the occupied spaces

nLimit the use of flexible ductwork upstream of the terminal unit

nApply a duct lining or duct silencer to the first section of the duct system in order to attenuate supply fan noise

nAdd balancing dampers upstream of diffusers in all noncritical branches

nIf needed, reducing transitions should be located several duct diameters upstream of terminal units

TRG-TRC014-EN

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Trane TRG-TRC014-EN manual Duct Design Recommendations, 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 Contents period one What Is Variable Air Volume?period two Components of a VAV SystemTRG-TRC014-EN What Is Variable Air Volume? What Is Variable Air Volume?Constant-Volume Variable-TemperatureSystem period oneWhat Is Variable Air Volume? Constant Volume-FullLoadperiod one period one Constant Volume-PartLoadWhat Is Variable Air Volume? Constant Volume-MultipleSpaces What Is Variable Air Volume?Constant Volume-MultipleSpaces period oneperiod one Terminal Reheat SystemWhat Is Variable Air Volume? Variable-Air-VolumeVAV System VAV-FullLoadWhat Is Variable Air Volume? period oneWhy VAV? Energy Savings VAV-PartLoadWhat Is Variable Air Volume? Why VAV?Why VAV? Comfort What Is Variable Air Volume?period one quiteperiod one System ComparisonWhat Is Variable Air Volume? VAV Building Characteristics Variable Thermal Load ProfilesWhat Is Variable Air Volume? period oneIndependent Space Control Common Return Air PathWhat Is Variable Air Volume? period oneperiod two Components of a VAV SystemComponents of a VAV System period twoComponents of a VAV System period twoVAV Terminal Units Single Duct, Cooling Only Components of a VAV Systemperiod two Single Duct, Cooling Onlyperiod two Space Heating with a VAV SystemComponents of a VAV System VAV Reheat primary airComponents of a VAV System period twoFan-PoweredTerminal Units Components of a VAV Systemperiod two parallelParallel, Fan-Powered plenum airParallel, Fan-Powered Components of a VAV Systemperiod two Series, Fan-PoweredComponents of a VAV System Parallel Versus Series Fan-Powered Series, Fan-PoweredComponents of a VAV System period twoperiod two Single-DuctVAV SystemsComponents of a VAV System Dual-Duct Components of a VAV Systemperiod two warm primary air cool primary air supply airVariable Air Volume to the Space warmcool Components of a VAV SystemConstant Air Volume to the Space Single-Fan, Dual-DuctVAV SystemComponents of a VAV System period twoperiod two Two-Fan, Dual-DuctVAV SystemComponents of a VAV System VAV Terminal Unit Controls Upstream Pressure Affects AirflowComponents of a VAV System period twoPressure-DependentControl Pressure-IndependentControlComponents of a VAV System period twoPrimary Airflow Measurement Terminal-UnitControl TechnologiesComponents of a VAV System 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 Components of a VAV System period twoDirect Digital Control DDC Electronic pressure transducer provides pressure-independentcontrolDiffusers Components of a VAV Systemperiod two DiffusersLinear Slot Diffuser Components of a VAV Systemperiod two Coandaperiod two Ceiling-DiffuserCompatibilityComponents of a VAV System Components of a VAV System period twoCeiling-DiffuserCompatibility cross TSupply Duct System Components of a VAV Systemperiod two Supply Duct SystemDuct Design Components of a VAV Systemperiod two Equal friction methodperiod two Duct Design RecommendationsComponents of a VAV System System Configurations System Configurationsperiod three period threeperiod three Perimeter SpacesSystem Configurations Perimeter SpacesBaseboard Perimeter Heating System Configurationsperiod three heat loss 450 Btu/hr/ftperiod three Overhead Supply Perimeter HeatingSystem Configurations System Configurations period threeVAV Reheat heat loss 250 Btu/hr/ftFan-PoweredVAV Dual-DuctVAVSystem Configurations period threeInterior Spaces Interior Spaces, Reheat RequiredSystem Configurations period threeSmall Buildings Changeover/Bypass VAV SystemSystem Configurations period threeSystem-LevelControl Modes System Configurationsperiod three System-LevelControl Modesperiod three Occupied ModeSystem Configurations period three Unoccupied ModeSystem Configurations period three Morning Warm-up/Cool-downModeSystem Configurations period four Fan ModulationFan Modulation period fourFan Modulation period fourSystem Resistance Curve Operating Point Riding the Fan CurveFan Modulation period fourperiod four Forward-CurvedCentrifugal FanFan Modulation Fan Modulation Curve Fan Modulationperiod four Fan Modulation CurveFan Control Loop VAV Fan ModulationFan Modulation period fourFan Modulation Methods Discharge DampersFan Modulation period fourFan Modulation period fourDischarge Dampers 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 pressureInlet Vanes Fan Modulationperiod four Inlet VanesFan-SpeedControl Fan Modulationperiod four Fan-SpeedControlVariable-PitchBlade Control Fan Modulationperiod four Variable-PitchBlade Controlperiod four Fan Modulation ComparisonsFan Modulation Controlling System Static Pressure Fan Outlet Static-PressureControlFan Modulation period fourSupply Duct Static-PressureControl Fan Modulationperiod four sensor located 2/3 down supply ductOptimized Static-PressureControl Fan Modulationperiod four sensor locatedperiod four Part-LoadComparisonFan Modulation period five Application Considerationsperiod five Application ConsiderationsApplication Considerations period fiveSystem-LevelVentilation Ventilation Reset Application Considerationsperiod five outdoor airflowFreeze Protection for Coils Measures to Prevent Coil Freeze-UpApplication Considerations period fivePart-LoadSpace Humidity Control Application Considerationsperiod five Part-LoadSpace Humidity Controlperiod five Part-LoadSupply Air TemperingApplication Considerations Building Pressure Control Direct Pressurization ControlApplication Considerations 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 period six ReviewReview period sixperiod six Review-PeriodTwofan-poweredVAV terminal unit ReviewReview-PeriodThree Review-PeriodFourReview period sixReview-PeriodFive Reviewperiod six System-levelventilationTRG-TRC014-EN Reviewperiod six Quiz Questions for PeriodQuestions 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