Allied A97UH2E - Troubleshooting: Cooling Sequence of Operation

508433-01 Issue 2345 Page 69 of 70
Troubleshooting: Cooling Sequence of Operation
1ST STAGE COOLING
REQUEST RECEIVED
ENERGIZE 1ST STAGE
COOLING CONTACTOR
(COMPRESSOR & FAN)
2ND STAGE
COOLING
REQUEST?
NO
YES
YES
YES
NO
1ST STAGE
COOLING REQUEST
STILL ACTIVE?
NO
YES
YES
ENERGIZE 2ND STAGE
COOLING CONTACTOR
(COMPRESSOR & FAN)
DE−ENERGIZE 2ND
STAGE COOLING
CONTACTOR
(COMPRESSOR & FAN)
NO
CONTROL WILL NOT RESPOND TO A 2ND STAGE COOLING REQUEST UNLESS A 1ST STAGE
COOLING REQUEST IS ACTIVE.
1
1
1
1
1
DE−ENERGIZE 1ST
STAGE COOLING
CONTACTOR
(COMPRESSOR & FAN)
2ND STAGE
COOLING REQUEST
STILL ACTIVE?
COOLING REQUEST
STILL ACTIVE?
CALL FOR COOLING
WAIT FOR COMPRESSOR TIMED
OFF DELAY TO EXPIRE
INDOOR BLOWER
SECOND ON DELAY
YES
1ST STAGE
DE−ENERGIZE INDOOR
BLOWER
ENERGIZE INDOOR BLOWER
(LOW COOLING MODE)
ENERGIZE INDOOR BLOWER
(HIGH COOLING MODE)
MAINTAIN INDOOR BLOWER
(HIGH COOLING MODE)
ENERGIZE AND MAINTAIN
INDOOR BLOWER AT
(LOW COOLING MODE)
MAINTAIN INDOOR
BLOWER
(LOW COOLING MODE)