GE AZ85E09DAC Technical Service Manual page 20

Automatic Defrosting of Indoor and Outdoor Coils
During continued compressor operation, there is potential for ice to form on the indoor coil when in cool
mode and for ice to form on the outdoor coil when in heat mode. The Zoneline is equipped with Automatic
Defrost to eliminate this potential problem.
Indoor coil defrost will occur when the indoor coil thermistor reads a temperature of 34°F or less for a
duration of 5 minutes. The main board will automatically shut the compressor off, allowing the indoor
coil temperature to rise. The fans will continue to operate throughout the defrost cycle for continued air
circulation. When the indoor coil thermistor detects a temperature of 50°F or above, the compressor will
resume normal operation. A 3-minute minimum compressor off time will be in effect.
Outdoor coil defrost will occur for one of the following reasons:
• The outdoor temperature thermistor reads a temperature of 14 °F or less for a duration of 2 hours and 59
minutes.
• The accumulated run time of the compressor is greater that 3 hours with an outdoor temperature of
32°F or less.
The outdoor coil is defrosted by reverse cycle defrosting (reversing the direction of the refrigerant fl owing
through the sealed system). This will cause hot refrigerant fl owing through the outdoor coil to quickly
and effi ciently melt any ice that has formed. Outdoor coil defrosting will terminate when the outdoor coil
thermistor reads a temperature of 68°F, or when a period of 9 minutes has elapsed, whichever comes fi rst.
When outdoor defrosting has been completed, the resistance heater(s) and fans will run for a minimum of 90
seconds or until the room has reached the thermostat set point.
Cool Mode Operation
Note:
• Minimum compressor/fans off time is 3 minutes +/- 10 seconds.
• Reversing valve is energized at all times in cool mode. Reversing valve is not de-energized when
thermostat is satisfi ed.
• Indoor and outdoor fans always operate at the same time in cool mode.
Indoor fan, outdoor
fan, compressor,
Currently Cooling
Set thermostat to
Currently Off thermostat to setting
reversing valve
energized.
cool. Adjust Indoor fan, outdoor
fan, reversing
below room valve energized.
temperature.
3
Compressor
SECOND
DELAY
– 20 –
Indoor fan, outdoor
Thermostat
fan, compressor
satisfied.
Thermostat not
energized. satisfied.
3 SECOND Indoor fan, outdoor
DELAY fan energized.
(Continued next page)
off.