hVac controls guide for Plans examiners and Building inspectors

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Plans ReviewSuggested Compliance Check(s):• If the building is taller than three stories and in climate zones 4 through 8,verify that motorized dampers are specified for outside air and exhaust/relief dampers on the mechanical floor plans or mechanical schedule.• Review the mechanical floor plans and mechanical schedule to locate control sequencesand verify that the design engineer has defined a procedure whereby dampers willbe closed and fans will be shut off when zones are unoccupied (figure 11).• For large spaces (greater than 500 ft2), check the mechanical and electrical floorplans to see that CO 2or other sensors are specified and tied in to the controlsystem to enable demand control ventilation (DCV) (figure 12).Figure 11: Sample control sequence showing damper controlOutside Air Damper Control: Outside air intake dampers shall open in response to a start signal. The dampersshall close and the fan shall stop in response to any of the following: stop signal, loss of control signal, loss ofelectrical power, or the AHU supply fan motor stops.Figure 12: Sample control sequence indicating DCVDemand Control of Ventilation: During occupied mode, zone requests for ventilation shall be determined basedon signals from zone-located CO2 sensors. A zone shall request ventilation when the CO2 concentration exceeds900ppm. In response to a request for ventilation, the system shall first increase the terminal unit airflow. Ifadditional ventilation is required, the system shall then increase the outdoor air rate at the air handler.Building InspectionSuggested Compliance Check(s):• Verify that outside air and exhaust/relief dampers have actuators that automatically open and close thedampers and that the dampers are in the closed position in spaces that are unoccupied (figure 13).• Verify that CO 2sensors included in the mechanical plans for the purpose of demandcontrol ventilation have been installed as shown in the plans (figure 14).• Review the mechanical plans and verify that automatic controls (i.e. occupancy sensor ormanual timers) have been provided for ventilation fans larger than 3/4 hp as shown.18 Control Requirements for All Systems
Figure 13: Motorized damperFigure 14: Top view of CO 2sensor (coin for scale)Additional Detail:a) DampersOutdoor air supply and exhaust/relief ducts shall have motorized dampers that automatically close whenthe spaces that they serve are not occupied. Buildings less than three stories tall or in climate zones 1through 3 may use gravity dampers.Code SectionsIECCASHRAE2009: 503.2.4.4 2007: 6.4.3.4.3,6.4.3.4.1, 6.4.3.4.22012: 403.2.4.4 2010: 6.4.3.4.2, 6.4.3.4.1b) Ventilation fan controlsFans with motors greater or equal to three-quarter horsepower, must have controls that can shut off fanswhen not required. This control may be an occupancy sensor, timer, or other device.Code SectionsIECCASHRAE2009: NA 2007: 6.4.3.4.52012: NA 2010: 6.4.3.4.4Control Requirements for All Systems 19
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: Figure 9: VSD installed on a supply
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 44 and 45: Figure 38: Sample control sequence
Page 46: Building Technology ProgramThe U.S.

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