Ventilation Override Module (Vom) - Trane SEHJ090-162 Installation, Operation And Maintenance Manual

Installation
– 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)

Important: The ventilation override system should not
be used to signal the presence of smoke
caused by a fire, as it is not intended nor
designed to do so.
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. A ventilation override mode can be initiated by
closing any of the five (5) corresponding binary inputs on
the VOM module. A binary output is provided on the VOM
module to provide remote indication of an active VOM
mode. All compressors, condenser fans and the
Humidification output are deenergized for any VOM
sequence.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 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
84
fan should be turned on with VFD at 100% speed and
exhaust fan should be turned off.
– Supply Fan - On
– 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 rooftop would become
negatively pressurized.This is desirable for clearing the
area of smoke from the now-extinguished fire, possibly
keeping smoke out of areas that were not damaged.
– Supply Fan - Off
– 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
– Supply Fan VFD - Max (if so equipped)
– Exhaust Fan - On; Exhaust Dampers - Open (if so
equipped)
– OA Dampers - Open; Return Damper - Closed
RT-SVX24J-EN