hVac controls guide for Plans examiners and Building inspectors

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Building InspectionSuggested Compliance Check(s):• Verify that fans 7.5 hp and greater have been provided with devicesfor fan speed control (e.g. VSD) (figure 36).• Confirm that the means of controlling fan speed identified in the approved mechanicaldesign, typically a building automation system, has been installed and is operational.Figure 36: Cooling tower motor — check for connection to VSDAdditional Detail:Code SectionsIECCASHRAE2009: 503.4.4 2007: 6.5.5.22012: 403.4.4 2010: 6.5.5.2Multi-zone SystemsLarge buildings typically have HVAC systems that can heat, cool, reheat, and recool air moving to multiplezones at the same time. Multiple-zone systems must have VAV controls capable of reducing the supply air toany zone before reheating, recooling, or mixing warm and cool air streams. IECC 2012 requires the supply airto be reduced to 30% of maximum, to 300 CFM, or to the level required for minimum ventilation before anyreheating, recooling or mixing. The requirements of ASHRAE are similar, though systems shown to reduceannual energy use by providing more supply air are allowed. ASHRAE 2010 also introduces a method forsystems with digital control of zone boxes to control the outdoor air intake based on the “zone ventilationefficiency” — the efficiency at which the system delivers outside air to the breathing zone.Plan ReviewSuggested Compliance Check(s):• Verify that control sequences include language for VAV system optimization(i.e. indicate that supply air is reduced prior to reheating/recooling):• Single duct VAV systems should reduce supply air before reheating/recooling takes place42 Control Requirements for Complex Systems
• Dual duct VAV systems should minimize the amount of hot/cold air mixing by reducing flow (figure 37)• Verify that language for supply air temperature reset is included in control sequences (figure 38)Figure 37: Sample control sequence for dual duct VAV systemOccupied Mode• Cooling○○Full cooling: Cold deck air damper opens to the maximum position.○○As cooling load decreases, cold deck air damper modulates more closed.○○No call for cooling: Cold deck air damper closes to the minimum position.• Heating○○Full heating: Hot deck air damper opens to the maximum position.○○As heating load decreases, hot deck air damper modulates more closed.○○No call for heating: Hot deck air damper closes to the minimum position.Control Requirements for Complex Systems 43
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 44 and 45: Figure 38: Sample control sequence
Page 46: Building Technology ProgramThe U.S.

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