YORK INTERNATIONAL
52
Sequence of Operation
FORM 100.50-NOM1 (604)
COMPRESSOR AVERAGE RUN TIMES
To increase system reliability, all compressors will
be staged up (ON) based on total run time. The com-
pres sors with the shortest total run time will always be
energized
Þ
rst in an attempt to equalize run time.
SUPPLY FAN OPERATION
Minimum Off Time
The Supply Fan minimum OFF time is as speci
Þ
ed in
Table 14 under section on Timeouts and Delays.
The Supply Fan will be ON prior to:
• Starting any compressors.
• Turning ON any gas or electric heat ing stage.
• Opening any heating valve.
Overrun
The Supply Fan will continue to run for 1 minute af-
ter all compressors or heating stages turn OFF unless
oth er wise stated. When in Thermostat operation, the
over run requirement will override the loss of the G input
from the Thermostat.
For gas or electric heat, the Supply Fan will continue
to run until the SAT is less than 100°F.
CV Operation
For CV operation:
• The Supply Fan will be ON whenever the G input
from the Thermostat is present.
• The Supply Fan will stay ON when the G input is no
longer present to satisfy the Overrun re quire ment.
• If the unit is con
Þ
gured to use a space sensor, the
Supply Fan will be ON whenever:
◦
Heating or cooling is called for.
◦
The
"Fan On with Sensor"
parameter is ON and
occupancy is indicated.
VAV & Flexsys Operation
For VAV operation:
• The Supply Fan will be ON at the speci
Þ
ed output
lev el whenever occupancy is indicated.
• When occupancy is not indicated the Supply Fan
will be ON at the speci
Þ
ed output level when-
ever:
◦
Unoccupied cooling or heating is called for.
◦
The Ther mo stat G input is present and the
VAV with Ther mo stat
parameter is ON.
• In the Heating Mode, the Supply Fan will be at
100% output when ON.
• In the Cooling Mode, the Supply Fan will be op-
er at ed to maintain the
Duct Static Pressure
setpoint
when ON.
Sequence of Operation
