Exceptional Case Of Mode Transition - Mitsubishi HMA100V Technical Manual

'10 • HM-T-149
Service
Operation control function by the indoor unit controller

Exceptional case of mode transition

In order to prevent water pipes on the system from freezing, there is some exception of mode transition when the outdoor air
temperature (BT1) drops below 0°C.
1) In (4) Cooling or (5) Hot water mode;
Operation changed to (3) Alternating mode of Heating with the lowest allowable temperature of supply water as the target.
If the supply water temperature does not reach the target, electric heater is forcibly activated regardless of the setting so that the
supply water temperature is kept at the lowest allowable temperature.
2) In (1) Auto or (2) AutoC mode and the condition to choose (5) Hot water mode is fulfilled; (3)Heating mode is chosen instead, and
the circulation pump operates at all time.
When the outdoor air temperature (BT1) exceeds 1°C, the exceptional operation is deactivated.
During combined mode of heating, it is also deactivated regardless of the outdoor air temperature (BT1) if the target temperature of
supply water exceeds its lowest allowable temperature plus 1°C.
- 126 -