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LGH/LCH036, 048, 060, 072, 074
B-Three-Stage Thermostat OR Room Sensor
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressors Off
Blower Cooling Low
Dampers modulate
Y2 Demand -
Compressors Off
Blower Cooling High
Dampers Modulate
Note - If dampers are at maximum open for three minutes,
compressor 1 is energized and blower stays on cooling high.
Y3 Demand -
Compressors 1 and 2 On
Blower High
Dampers Maximum Open
072H UNITS
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 - During a dehumidification demand the blower
operates at low speed. 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 On
Dampers modulate
Note - If dampers are at maximum open for three
minutes, compressor is energized.
Y2 Demand -
Compressors On
Blower Cooling On
Dampers Modulate
2-No Economizer or Outdoor Air Not Suitable
Y1 Demand -
Compressor 1 On
Blower Cooling On
Dampers Minimum Position
036U, 048U, 060U, 074U UNITS
A-Two-Stage Thermostat
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressor Off
Blower Low
Dampers modulate
Y2 Demand -
Compressor Low
Blower Low
Dampers Full Open
Note - Compressor is energized after damper has been
at full open for three minutes.
2-No Economizer or Outdoor Air Not Suitable
Y1 Demand -
Compressor Low
Blower Low
Dampers Minimum Position
Y2 Demand -
Compressor High
Blower High
Dampers Minimum Position
B-Three-Stage Thermostat OR Room Sensor
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressors Off
Blower Low
Dampers Modulate
Y2 Demand -
Compressor Low
Blower Low
Dampers Full Open
Note - Compressor is energized after damper has been
at full open for three minutes.
Y3 Demand -
Compressor High
Blower High
Dampers Full Open
2-No Economizer or Outdoor Air Not Suitable
Y1 Demand -
Compressor Low
Blower Low
Dampers Minimum Position
Y2 Demand -
Compressor High
Blower High
Dampers Minimum Position
Y3 Demand -
Compressor High
Blower High
Dampers Minimum Position
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