40
2-16. 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.
1
If the room temperature thermistor RT11 reads more than set temperature, COOL mode is selected.
2
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.
1
COOL mode changes to HEAT mode when 15 minutes have passed with the room temperature 2 degrees below the
set temperature.
2
HEAT mode changes to COOL mode when 15 minutes have passed with the room temperature 2 degrees 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: If two or more indoor units are operating in multi system, there might be a case that the indoor unit, which is
operating in AUTO ( ), cannot change over the other operating mode (COOL
HEAT) and becomes a
state of standby.
(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.
High
Med.
Low
High
Rotational frequency
time
2-17. 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 feedback
the rotational frequency. Comparing the current rotational frequency with the target rotational frequency (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.
(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 lock-up, POWER lamp flashes on and off to show the fan motor abnormality.
OBT14A--2qxp 06.1.12 1:08 PM Page 40