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4-5. INDOOR FAN MOTOR CONTROL
(1) Rotational frequency feedback control
The indoor fan motor is equipped with a rotational frequency sensor, and outputs signal to the microprocessor to feed-
back the rotational frequency. Comparing the current rotational frequency with the target rotational frequency (Super High,
High, Med., Low), the microprocessor adjusts fan motor electric current to make the current rotational frequency close
to the target rotational frequency. With this control, when the fan speed is switched, the rotational frequency changes
smoothly.
High
Med.
Low
Super High
Super High
time
Rotational frequency
(2) Fan motor lock-up protection
When the rotational frequency feedback signal has not output for 12 seconds, (or when the microprocessor cannot
detect the signal for 12 seconds) energizing to the fan motor is stopped. Then the microprocessor retries detection 3
times every 30 seconds. If the microprocessor still cannot detect the signal, the fan motor is regarded locked-up. When
the fan motor locks up, OPERATION INDICATOR lamp flashes ON and OFF to show the fan motor abnormality.
4-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION
Once desired temperature is set, unit operation is switched automatically between COOL and HEAT operation.
1. Mode selection
(1) Initial mode
At first, indoor unit operates only indoor fan with outdoor unit OFF for 3 minutes to detect present room temperature.
Following the conditions below, operation mode is selected.
If the room temperature thermistor RT11 reads more than set temperature, COOL mode is selected.
If the room temperature thermistor RT11 reads set temperature or less, HEAT mode is selected.
(2) Mode change
In case of the following conditions, the operation mode is changed.
COOL mode changes to HEAT mode when 15 minutes have passed with the room temperature 35.6°F below the set
temperature.
HEAT mode changes to COOL mode when 15 minutes have passed with the room temperature 35.6°F above the set
temperature.
In the other cases than the above conditions, the present operation mode is continued.
NOTE1:
Mode selection is performed when multi standby (refer to
NOTE2
) is released and the unit starts operation with
ON-timer.
NOTE2:
When two or more indoor units are operating simultaneously, the indoor unit, which is operating in AUTO ( ),
might not be able to change over the operating mode (COOL
HEAT) and becomes the standby state.
(3) Indoor fan control/ Vane control
As the indoor fan speed and the horizontal vane position depend on the selected operation mode, when the operation
mode changes over, they change to the exclusive ones.
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