77
YORK INTERNATIONAL
FORM 100.50-NOM1 (604)
5
Sequence of Operation
• Disable the Exhaust Fan, if activated.
• Turn ON the Supply Fan full (VFD to 100%).
• Energize the VAV Heat Relay and drive all VAV
boxes open.
• Open the Outside Air dampers full.
• Close the Return Air damper full.
Maintain this operation until the Smoke Purge input is
deactivated, then return to normal operation.
Setting #3, Exhaust
If the smoke purge setting is set to 3 and the Smoke
Purge input is activated, the unit will do the follow-
ing:
• Disable the Supply Fan.
• Close the Outside Air damper(s).
• Turn ON the Exhaust Fan full (VFD/ED to 100%)
Maintain this operation until the Smoke Purge input is
deactivated, then return to normal operation.
Setting #4, Purge
If the smoke purge setting is set to 4 and the Smoke
Purge input is activated, the unit will do the follow-
ing:
• Turn ON the Supply Fan full (VFD to 100%).
• Energize the VAV Heat Relay and drive all VAV
boxes open.
• Turn ON the Exhaust Fan full (VFD/ED to
100%).
• Open the Outside Air Damper(s) full.
• Close the Return Air Damper full.
Maintain this operation until the Smoke Purge input is
deactivated, then return to normal operation.
Setting #5, Purge w/ Duct Pressure Control
If the smoke purge setting is set to 5 and the Smoke
Purge input is activated, the unit will do the follow-
ing:
• Supply Fan
◦
VAV units - Turn ON the Supply Fan VFD and
con trol to the Duct Static Setpoint.
◦
CV - Turn ON fan (variable output is 100%)
• Turn ON the Exhaust Fan full (VFD/ED to 100%)
• Open the Outside Air Damper(s) full.
• Close the Return Air Damper full.
Maintain this operation until the Smoke Purge input is
deactivated, then return to normal operation.
RETURN FAN OPERATION
The following is an explanation of the different modes
of operation for the return fan option
No Outdoor Air, 100% Return Air, VFD Supply
Air Fan, No Exhaust
This con
Þ
guration would be for applications where the
supply fan performance cannot meet the total static re-
quirement of the duct system. This allows the external
static pressure to be split between the return air and
supply air fan.
• Application uses two return air fans each with
there own motor being controlled by a single VFD
drive.
• The return fan VFD drive is controlled by a pressure
transducer with a static pressure probe located in
the return section of the unit.
• The return fan VFD is programmed to maintain -
.03 to -.05 inches of WC static at the probe. These
values are programmed into the VFD at the factory.
The value can be veri
Þ
ed by checking item # 204
and 205 in Menu 2 (References and Limits) in the
VFD program. Refer to Installation, Operation
& Maintenance Form 100.40-N04 for additional
information.
• The supply air VFD is controlled by the duct static
transducer.
• The supply air blower and return air fan will always
be energized together.
• As the pressure in the return air section becomes
more negative the return air fan will speed up. As
the pressure in the return section increases above
the setting the return air fan will slow down
No Outside Air, 100% Return Air, VFD Supply
Fan, with Motorized Exhaust Damper
This con
Þ
guration would be used for applications where
the supply fan performance cannot meet the total static
requirement of the duct system and there is make up
air units or other outside air sources supplying air to
the space. This allows the external static pressure to
be split between the return air and supply air fan while
removing the excess air from the building.