Mitsubishi Electric MSC-GE-VB Service Manual page 8

1-4. 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 (High,
Med., Low), the microprocessor controls SR141 and 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 fre-
quency 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) the fan motor is regarded locked-up. Then the electric current to the fan motor is shut-
off. 3 minutes later, the electric current is applied to the fan motor again. During the fan motor lock-up, the OPERATION
INDICATOR lamp flashes ON and OFF to show the fan motor abnormality.
1-5. AUTO VANE OPERATION (MSC, MSH)
1. Horizontal vane
(1) Cold air prevention in HEAT operation
When any of the following conditions occur in HEAT operation, the vane angle changes to Angle 1 automatically to pre-
vent cold air blowing on users.
Compressor is not operating.
Defrosting is performed.
Indoor coil thermistor reads 24°C or below.
Indoor coil thermistor temperature is rising from 24°C or below until it reaches 28°C.
Indoor coil thermistor temperature
NOTE1: If the temperature of the indoor coil thermistor reads from 24 to 28°C at the air conditioner starting, this control
works.
NOTE2: When 2 or more indoor units are operated with multi outdoor unit, even if any indoor unit turns thermostat OFF, this
control does not work in the indoor unit.
Rotational frequency
High
Med.
Cold Air Prevention
8
High
Low
time
Released
24°C
Horizontal vane
Set position
Angle 1
28°C