Carrier 42HWG009 Technical Data & Service Manual page 23

Indoor Coil High Temperature Protection
– The system performs this function only in HEAT mode.
– If the indoor coil temperature is greater than or equal to 57°C, the outdoor fan turns off and
does not turn on until the indoor coil temperature is less than or equal to 49°C.
– If the indoor coil temperature is greater than or equal to 62°C, the compressor turns off
until the indoor coil temperature is less than or equal to 42°C. The 3 min. time delay of
compressor is applied in this case.
OUTDOOR FAN
ON
COMPRESSOR
ON
42° C
Defrost
– In HEAT mode, outdoor coil may be frosted, which cause decrease of the unit perfor-
mance. Therefore the microcomputer of the unit turns on or off the compressor to re-
move the frost.
– The defrost operation is performed as follows:
• Defrost initiation
1) On the basis of the demand condition considering the difference between indoor
coil temperature and indoor room temperature, controller decides defrost initiation
after satisfying two steps of preceding condition.
49° C
22
57° C 62° C
INDOOR COIL TEMP.
OFF
OFF