Fm Control With The Heating Thermostat Turned Off; Hot Start (Cold Draft Prevention During Heating); Indoor Fan Control During Defrost Operation (Only Heat Pump Type) - Mitsubishi FDC 6 Series Service Manual

6) FM control with the heating thermostat turned off (For cold draft prevention) (Only heat pump type)
In order to prevent a cold draft while the heating thermostat is turned off, the indoor blower is controlled in response to the
temperature of the indoor heat exchanger as illustrated below. It should be noted that if SW3-4 on the indoor PCB is turned off, the
indoor blower will stop so far as the temperature of the indoor heat exchanger is lower than 40˚C. It will be turned to the Lo
operation 5 minutes later.
Lo
40
7) Hot start (Cold draft prevention during heating) (Only heat pump type)
1) If the indoor heat exchanger temperature is lower than 30˚C when the heating operation has started, the following indoor
blower control is performed.
(1) In case of the thermostat off condition: Lo operation
(2) In case of the thermostat on condition : Stop
(3) If the indoor heat exchanger temperature exceeds 30˚C or 7 minutes after the beginning of hot start, the hot start
terminates and it returns to the setting airflow of the blower.
2) If the indoor heat exchanger temperature is lower than 30˚C when the unit is heating under the thermo-ON condition, the
indoor fan operates in the Lo mode. As the temperature rises higher than 30 ˚C or 7 minutes after the beginning of hot start,
the hot start terminates and it returns to the setting air flow.
8)

Indoor fan control during defrost operation (Only heat pump type)

1) The indoor fan operation is changed from the setting airflow to the Lo operation 40 seconds before the start of defrost
operation (when the defrost thermostat is turned ON) and stops if the indoor heat exchanger temperature drops below 20˚C.
2) After the stop as described in 1)-above, the control will be conducted as illustrated below depending on the indoor heat
exchanger temperature.
3) If the indoor heat exchanger temperature rises beyond 30˚C of 7 minutes after the end of defrosting, the indoor fan control
related to the defrosting is completed.
(Setting air flow)
Note (1) After the thermostat is reset, it returns to the hot start
45
Stop
20
Indoor heat exchanger temperature(˚C)
control.
Lo
30
5