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Cooling Operation
This is a summary of cooling operation. Refer to the
sequence of operation provided in the Engineering
Handbook or Service Manual for more detail.
Note - Free cooling is locked-out during reheat operation.
Refer to hot gas reheat start-up and operation section for
details.
A-Two-Stage Thermostat
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressors Off
Blower Cooling Low
Dampers modulate
Note - If dampers are at maximum open for five minutes,
compressors are energized and blower stays on cooling
high.
Y2 Demand -
Compressors Modulate
Blower Cooling High
Dampers Maximum Open
2-No Economizer or Outdoor Air Not Suitable
Y1 Demand -
Compressors Modulate
Blower Cooling Low
Dampers Minimum Position
Y2 Demand -
Compressors Modulate
Blower Cooling High
Dampers Minimum Position
B-Three-Stage Thermostat
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressors Off
Blower Cooling Low
Dampers Modulate
Note - If dampers are at maximum open for five minutes,
compressors are energized and blower stays on cooling
high.
Y2 Demand -
Compressors Modulate
Blower Cooling Intermediate
Dampers Maximum Open
Y3 Demand -
Compressors Modulate
Blower Cooling High
Dampers Maximum Open
C-Room Sensor
1-Economizer With Outdoor Air Suitable
Compressors Off
Blower Modulates
Dampers modulate
Note - If dampers are at maximum open for five minutes,
compressors are energized and the blower modulates.
2-No Economizer or Outdoor Air Not Suitable
Compressors Modulate
Blower Modulates
Dampers Minimum Position
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