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LGM/LCM036, 048, 060, 074
Cooling Operation
A-Two-Stage Thermostat
1-Economizer With Outdoor Air Suitable
Y1 Demand -
Compressor Off
Blower Low
Dampers Modulate
Y2 Demand -
Compressor Modulates
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 Modulates
Blower Low
Dampers Minimum Position
Y2 Demand -
Compressor Modulates
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 Modulates
Blower Low
Dampers Full Open
Note - Compressor is energized after damper has been at
full open for three minutes.
Y3 Demand -
Compressor Modulates
Blower High
Dampers Full Open
2-No Economizer or Outdoor Air Not Suitable
Y1 Demand -
Compressor Modulates
Blower Low
Dampers Minimum Position
Y2 Demand -
Compressor Modulates
Blower Mid
Dampers Minimum Position
Y3 Demand -
Compressor Modulates
Blower High
Dampers Minimum Position
C-Zone Sensor
1-Economizer With Outdoor Air Suitable
Low Cooling Demand -
Compressor Off
Blower Variable
Dampers Modulate
High Cooling Demand -
Compressor Variable
Blower Variable
Dampers Full Open
Note - Compressor is energized after damper has been at
full open for three minutes.
Note - Free cooling is locked out when a dehumidification
demand is received. The unit operates in
dehumidification mode as if the outdoor air is not suitable
.
2-No Economizer or Outdoor Air Not Suitable
Any Demand -
Compressor Variable
Blower Variable
Damper Minimum Position
D-Verify Proper Operation In Zone Sensor Mode
The Unit Controller (A55) communicates the appropriate
frequency (speed) to the compressor inverter (A192) to
match the cooling load. Because the cooling load varies,
the Unit Controller provides a test mode to initiate a
predictable compressor speed. Use the following mobile
service app menu paths to change the compressor speed
and verify discharge and suction pressures are changing
appropriately. When the compressor speed
increases
,
the discharge pressure will
increase
proportionately and
the suction pressure will
decrease
proportionately. When
the compressor speed
decreases
, the discharge
pressure will
decrease
proportionately and the suction
pressure will
increase
proportionately.
036, 048, 060U
High speed compressor operation:
SERVICE > TEST > COOL > COOL 3
Intermediate speed compressor operation:
SERVICE > TEST > COOL > COOL 2
Low speed compressor operation
SERVICE > TEST > COOL > COOL 1
074U Only
High speed compressor operation:
SERVICE > TEST > COOL > COOL 4
First intermediate speed compressor operation:
SERVICE > TEST > COOL > COOL 3
Second intermediate speed compressor operation:
SERVICE > TEST > COOL > COOL 2
Low speed compressor operation
SERVICE > TEST > COOL > COOL 1
