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RT-PRC031-EN 17
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 now-extinguished
fire, possibly keeping smoke out of
areas that were not damaged.
– 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