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1. Thermostat control
Refer to MXZ MICROPROCESSOR CONTROL, HEAT OPERATION (3-10.1.).
4-3. HEAT ( ) OPERATION
2. Indoor fan speed control
(1) Indoor fan operates at the set speed by FAN SPEED CONTROL button.
In Auto the fan speed is as follows.
3. High pressure protection
In HEAT operation, the indoor coil thermistor detects the temperature of the indoor heat exchanger. The compressor opera-
tional frequency is controlled to prevent the condensing pressure from increasing excessively.
4. Defrosting
Refer to MXZ MICROPROCESSOR CONTROL, HEAT DEFROSTING CONTROL (3-4.).
(2) Cold air prevention control
When the compressor is not operating:
( ) If the temperature of room temperature thermistor RT11 is less than 66.2°F, the fan stops.
( ) If the temperature of room temperature thermistor RT11 is 66.2°F or more and
(
) if the temperature of indoor coil thermistor is less than 32°F, the fan stops.
( ) if the temperature of indoor coil thermistor is 32°F or more, the fan operates at Very Low.
When the compressor is operating:
(
) If the temperature of indoor coil thermistor is 104°F or more, the fan operates at set speed.
( ) If the temperature of indoor coil thermistor is less than 104°F and
( ) if heating operation starts after defrosting, the fan stops.
(
) if the temperature of room temperature thermistor RT11 is 66.2°F or less, the fan stops.
(
) if the temperature of room temperature thermistor RT11 is more than 66.2°F, the fan operates at Very Low.
NOTE: • When 2 or more indoor units are operated with a multi type outdoor unit, the fan operates intermittently at Very
Low or stops in the thermostat-OFF units while at least one unit is thermostat-ON.
• When 3 minutes have passed since the compressor started operation, this control is released regardless of the
temperature of RT11 and indoor coil thermistor.
Time chart of defrosting in HEAT mode (reverse type)
set position
set speed
set position
set speed
Indoor fan (upper)
vertical
Horizontal vane
Very Low (temperature of indoor coil thermistor > 64.4°F)
30
seconds
OFF
Damper
Indoor fan (lower)
OFF
CLOSE
ON
ON
OPEN or CLOSE
OPEN or CLOSE
<Indoor unit>
High
Med.
Low
Fan speed
Set temperature minus room
temperature (During operation)
Set temperature minus
room temperature (Initial)
Between 0.45 and 3.6°F
3.6°F(2°C) or more
Less than 0.45°F(0.25°C)
0.45°F
(0.25°C)
3.15°F
(1.75°C)
3.6°F
(2°C)
7.2°F
(4°C)