hVac controls guide for Plans examiners and Building inspectors
hVac controls guide for Plans examiners and Building inspectors hVac controls guide for Plans examiners and Building inspectors
Figure 38: Sample control sequence for supply air temperature resetSupply Air Temperature ResetWhen occupied, the supply air temperature(SAT) is reset from 53°F to 65°F using thefollowing logic:• When the outside air temperature (OAT) is70°F and above, SAT shall be 53°F.• When OAT is 65°F to 70°F, the SAT isreset based on system demand betweenminimum and maximum values that varylinearly with temperature (see figure).• When OAT is below 65°F, reset SATbetween 55°F and 65°F based on systemdemand.• System demand is determined using a trimand respond logic:○○When the fan is off, SAT is at 65°F○○When the fan is on, every 2 minutes:◗◗◗◗Increase the SAT setpoint by 0.2°F if there are no zone cooling requests*If there are more than two cooling requests, decrease the setpoint by 0.3°F* cooling requests are generated when the cooling loop of any zone served is >99%Source: EnergyDesignResources, Advanced Variable Air Volume System Design Guide, March 2007SAT Setpopint65°F55°F53°F65°F 70°FOATBuilding InspectionSuggested Compliance Check(s):• Confirm that the building automation system specified in the approved design is installed and operational.• Checking that multi-zone VAV systems are optimized is an intensive procedure, wellbeyond the scope of building inspection. However, ASHRAE 90.1-2010 and IECC 2012require commissioning to be performed on many commercial buildings. The commissioningprovider’s report should describe how the system was tested and optimized.Additional Details:a) Multi zone VAV system optimization controlSystems with digital control of zone boxes must automatically adjust supply air in response to changesin system ventilation efficiency. This approach allows outside air supply to be provided at below designrates, so long as the zone that is least effective in delivering outside air to the breathing zone maintainsacceptable indoor air quality. Detailed guidance on this approach is provided in ASHRAE Standard 62.1.44 Control Requirements for Complex Systems
Code SectionsIECCASHRAE2009: NA 2007: NA2012: NA 2010: 6.5.3.3b) Single duct VAV systemsTerminal Units shall reduce supply of supply air to 30% of maximum, to 300 CFM, or to a level sufficient toprovide the minimum required ventilation before reheating/recooling.Code SectionsIECCASHRAE2009: 503.4.5.1 2007: - 6.5.2.12012: 403.4.5.1 2010: 6.5.2.1c) Dual duct VAV systemsDual duct systems shall have terminal units that can minimize flow from one duct to 30% of maximum, to 300CFM, or to a level sufficient to provide the minimum required ventilation prior to mixing from second duct.Code SectionsIECCASHRAE2009: 503.4.5.2 2007: 6.5.2,12012: 403.4.5.2 2010: 6.5.2.1d) Supply air temperature resetSupply air temperature (SAT) reset is required for multi zone HVAC systems. SAT must be reset in responseto building load or outside air temperature. The controls must allow SAT reset that is at least 25 percent ofthe difference between the design SAT and room air temperature.Code SectionsIECCASHRAE2009: 503.4.5.4 2007: NA2012: 403.4.5.4 2010: 6.5.3.4
- Page 2 and 3: ContentsIntroduction ..............
- Page 5 and 6: Commercial buildingControl requirem
- Page 7 and 8: Prescriptive requirementsfor Comple
- Page 9 and 10: Code Requirements andCompliance Che
- Page 11 and 12: Control Requirements for All System
- Page 13 and 14: Figure 4: Sample control sequence s
- Page 15 and 16: d) Automatic setback and shutdown c
- Page 17 and 18: Figure 9: VSD installed on a supply
- Page 19 and 20: Figure 13: Motorized damperFigure 1
- Page 21 and 22: Building InspectionSuggested Compli
- Page 23 and 24: 4) The supply of outside air is red
- Page 25 and 26: ) Control strategyEconomizers must
- Page 27 and 28: 4) The supply of outside air is red
- Page 29 and 30: must be positioned well down the du
- Page 31 and 32: Figure 23: BAS screen shot indicati
- Page 33 and 34: Code SectionsIECCASHRAE2009: NA 200
- Page 35 and 36: Figure 27: Illustrated control sequ
- Page 37 and 38: Code SectionsIECCASHRAE2009: 503.4.
- Page 39: Building InspectionSuggested Compli
- Page 42 and 43: Building InspectionSuggested Compli
- Page 46: Building Technology ProgramThe U.S.
Code SectionsIECCASHRAE2009: NA 2007: NA2012: NA 2010: 6.5.3.3b) Single duct VAV systemsTerminal Units shall reduce supply of supply air to 30% of maximum, to 300 CFM, or to a level sufficient toprovide the minimum required ventilation be<strong>for</strong>e reheating/recooling.Code SectionsIECCASHRAE2009: 503.4.5.1 2007: - 6.5.2.12012: 403.4.5.1 2010: 6.5.2.1c) Dual duct VAV systemsDual duct systems shall have terminal units that can minimize flow from one duct to 30% of maximum, to 300CFM, or to a level sufficient to provide the minimum required ventilation prior to mixing from second duct.Code SectionsIECCASHRAE2009: 503.4.5.2 2007: 6.5.2,12012: 403.4.5.2 2010: 6.5.2.1d) Supply air temperature resetSupply air temperature (SAT) reset is required <strong>for</strong> multi zone HVAC systems. SAT must be reset in responseto building load or outside air temperature. The <strong>controls</strong> must allow SAT reset that is at least 25 percent ofthe difference between the design SAT <strong>and</strong> room air temperature.Code SectionsIECCASHRAE2009: 503.4.5.4 2007: NA2012: 403.4.5.4 2010: 6.5.3.4
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