Reverse Cycle Defrosting Heat Pump Mode - GE AZ45E07EA Series Technical Service Manual

Reverse Cycle Defrosting Heat Pump Mode

Reverse Cycle Defrost shall be controlled as a function of compressor run time and outdoor coil temperature.
a) Defrost Enable
The reverse cycle defrost shall begin when either:
1. The control detects that the outdoor coil
temperature has remained below 14°F for
more than 3 minutes.
-OR-
2. The accumulated run time of the compressor
is greater than 3 hours, provided that the
outdoor temperature stays below 32°F.
REVERSE CYCLE DEFROST
Compressor
Outdoor Fan
Indoor Fan
Reversing
Valve
Heaters
On
ON (Reverse Cycle)
Max 9 mins
Min 3 mins
On
On
On
T1
– 22 –
b) Defrost Operating Sequence
When either conditions is detected (outdoor coil
remaining below 14°F for more than 3 minutes
OR the accumulated run time of the compressor
is greater than 3 hours, provided that the outdoor
temperature stays below 32°F) the Zoneline will
initiate a reverse cycle defrost. The following
steps comprise the reverse cycle defrost:
1. Immediately stop heat pump operation
2. Run stage 3 heating until room temperature
3. Run reverse cycle defrost (cooling mode
without fans) until the outdoor coil
temperature reaches 62°F or 9 minutes of
defrost time.
4. Run a stage 3 heating cycle to satisfy room
temperature
5. Resume normal heating mode logic.
On
On
On
T2
On
On
On