Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 177

[ VII Control ]
(2) Heating operation
1. Indoor unit fan operation at
Very Low speed
2. Inverter output 0Hz
3. Indoor unit LEV, LEV1 Fully closed
4. All solenoid valves OFF
5. Outdoor unit fan stop
6. 52C1 OFF
*Note 1. When outdoor unit starts defrosting, it transmits defrost operations command to indoor unit, and the indoor unit starts
defrosting operations. Similarly when defrosting operation stops, indoor unit returns to heating operation after receiving
defrost end command of outdoor unit.
*Note 2. Defrost end condition: 10 or more minutes must pass after defrost operation.
or
Outdoor unit piping temperature: refer to "-7-. Defrost operation control" of [2] Controlling the Outdoor Unit.
Heating operation
*Note 1,2
YES
Defrost
operation
NO
4-way valve ON
YES
Test run mode
ON
NO
NO
Thermostat ON
YES
YES
3-minute restart
prevention
NO
1. Indoor/outdoor unit fan control
2. Inverter frequency control
3. Indoor unit LEV, LEV1 control
4. Solenoid valve control
5. 52C1 control
- 168 -
Normal operation
Defrost operation
Unit in the stopped state
During test run mode
4-way valve OFF
1. Indoor unit fan stops
2. Inverter defrost frequency control
3. Indoor unit LEV fully closed.
4. Solenoid valve control
5. Outdoor unit fan stop
6. LEV1 control
7. 52C1 control
*Note 1,2
NO
Stopping the
defrost operation
YES
Stopping the defrost
operation
Return to heating
operation