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18
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1.4.12 Protective control function
(1) Frost prevention for indoor heat exchanger [Preventing frost accumulation on the indoor heat exchanger]
During the Cooling or Dry operation in low room air temp. condition, evaporating temperature will decrease and consequently
indoor heat exchanger sometimes gets clogged with frost (or ice).
In order to prevent this trouble, compressor is stopped by under mentioned condition by indoor heat exchanger sensor (Th
2) and
timer (built into microcomputer circuit) functions.
Also indoor fan is changed over to protects the fan tap just before frost prevention control.
CM, FM
O stoppage condition
1 Temperature of heat exchanger is
2.5˚C or lower.
2 As least 3 minutes has passed since
the compressor started.
Indoor heat exchanger
temperature (˚C)
CM, FMO re-starting condition
1 Temperature of heat exchanger is
8˚C or higher.
Set fan
speed
Protects
the fan
tap just
before
frost
prevention
control
(2) Three-minute forced operation
When the compressor begins operating the thermal operation is not effective for 3 minutes, so operation continues as is in the
operation mode. (After 3 minutes has passed the thermal operation is effective.)
However, stopping the compressor via a stop signal or protection control has priority.
(3) Self diagnosis function
When something abnormal happens on the outdoor unit, indoor unit fan motor and each sensor (heat exchanger, room temperature),
it will be indicated by flashing lights.
(a) Abnormality of outdoor unit: When the indoor heat exchanger temperature does not fall to 25°C or below for 40 minutes
after 5 minutes have elapsed since the compressor operation start, the abnormality stop
occurs. (The timer light flashes 2 times.)
(b) Abnormality of indoor fan motor: The indoor fan motor revolves at a rate under 300 rpm for 30 seconds or longer, the
RUN light will flash.
(c) Abnormality of heat exchanger sensor: RUN light will flashing when the input temperature of the heat exchanger
sensor measures less than –20°C for more than 15 seconds with the air
conditioner “OFF”. (will not flashing during operation)
(d) Abnormality room temperature sensor: RUN light will flashing when the input temperature of the room temperature
sensor measures less than –20°C for more than 15 seconds with the air
conditioner “OFF”. (will not flashing during operation)
Note (1) If the above abnormalities happen concurrently, the light will flashing in the order of item number (a) through (d) above.
2.5 8
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