Controls VAV and CV
–Return VFD - Max (if so equipped)
4.EMERG_SHUTDOWN:
–Supply Fan - Off
–Supply Fan IGV / Supply Fan VFD - Closed/Min (if so equipped)
–Exhaust Fan - Off; Exhaust Dampers Closed (if so equipped)
–OA Dampers - Closed; Return Damper - Open
–Heat - All heat stages off; Mod Heat output at 0 vdc
–Occupied/Unoccupied/VAV box output - Energized
–VOM Relay - Energized (if so equipped)
–Preheat Output - Off
–Return Fan - Off; Exhaust Dampers - Closed (if so equipped)
–Return VFD - Min (if so equipped)
5.EMERG_FIRE - Input from fire pull box/system:
–Supply Fan - Off
–Supply Fan IGV / Supply Fan VFD - Closed/Min (if so equipped)
–Exhaust Fan - Off; Exhaust Dampers Closed (if so equipped)
–OA Dampers - Closed; Return Damper - Open
–Heat - All heat stages off; Mod Heat output at 0 vdc
–Occupied/Unoccupied/VAV box output - Energized
–VOM Relay - Energized (if so equipped)
–Preheat Output - Off
–Return Fan - Off; Exhaust Dampers - Closed (if so equipped)
–Return VFD - Min (if so equipped)
Ventilation Override Module (VOM)
The user can customize up to five (5) different override sequences for purposes of ventilation override control. If more than one VOM
sequence is being requested, the sequence with the highest priority is initiated first. Sequence hierarchy is the sequence “A” (UNIT OFF) is first, with sequence “E” (PURGE with Duct Pressure Control) last.
The factory default definitions for each mode are as follows:
1.UNIT OFF sequence “A”
When complete system shutdown is required the following sequence can be used.
–Supply Fan - Off
–Supply Fan IGV / Supply Fan VFD - Closed/Min (if so equipped)
–Exhaust Fan - Off; Exhaust Dampers Closed (if so equipped)
–OA Dampers - Closed; Return Damper - Open
–Heat - All heat stages off; Mod Heat output at 0 vdc
–Occupied/Unoccupied/VAV box output - Deenergized
–VOM Relay - Energized
–Preheat Output - Off
–Return Fan - Off; Exhaust Dampers - Closed (if so equipped)
–Return VFD - Min (if so equipped)
–OA Bypass Dampers - Open (if so equipped)
–Exhaust Bypass Dampers - Open (if so equipped)
2.PRESSURIZE sequence “B”
Perhaps a positively pressurized space is desired instead of a negatively pressurized space. In this case, the supply fan should be turned on with inlet guide vanes open/VFD at 100% speed and exhaust fan should be turned off.
–Supply Fan - On
–Supply Fan IGV / Supply Fan VFD - Max (if so equipped)
–Exhaust Fan - Off; Exhaust Dampers Closed (if so equipped)
–OA Dampers - Open; Return Damper - Closed
–Heat - All heat stages off; Mod Heat output at 0 vdc
–Occupied/Unoccupied/VAV box output - Energized
–VOM Relay - Energized
–Preheat Output - Off
–Return Fan - Off; Exhaust Dampers - Closed (if so equipped)
–Return VFD - Min (if so equipped)
–OA Bypass Dampers - Open (if so equipped)
–Exhaust Bypass Dampers - Open (if so equipped)
3.EXHAUST sequence “C”
With only the exhaust fans running (supply fan off), the space that is conditioned by the air handler would become negatively pressurized. This is desirable for clearing the area of smoke from the
–Supply Fan - Off
–Supply Fan IGV / Supply Fan VFD - Closed/Min (if so equipped)
–Exhaust Fan - On; Exhaust Dampers Open (if so equipped)
–OA Dampers - Closed; Return Damper - Open
–Heat - All heat stages off; Mod Heat output at 0 vdc
–Occupied/Unoccupied/VAV box output - Deenergized
–VOM Relay - Energized
–Preheat Output - Off
–Return Fan - On; Exhaust Dampers - Open (if so equipped)
–Return VFD - Max (if so equipped)
–OA Bypass Dampers - Open (if so equipped)
–Exhaust Bypass Dampers - Open (if so equipped)
4.PURGE sequence “D”
Possibly this sequence could be used for purging the air out of a building before coming out of Unoccupied mode of operation on VAV units or for the purging of smoke or stale air if required after a fire.
–Supply Fan - On
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