GEAppliances AZ75E09DAC, Technical Service Manual

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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
flowing through the sealed system). This will cause hot refrigerant flowing through the outdoor coil to
quickly and efficiently 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 first. 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.
Ventilation Control
The ventilation control lever is located on the left
side of the Zoneline unit, behind the front case
panel.
When the lever is in the CLOSE position, only air
inside the room is circulated and filtered.
When the lever is in the OPEN position, some
outdoor air will be drawn into the room. This will
reduce the heating or cooling efficiency.
Vent control
(push lever down
and pull forward
or back to
operate)
Open
Close