Heat Operation - Mitsubishi Electric MSZ-AY25VG-ET1 Service Manual

9-4. HEAT ( ) OPERATION
(1) Press OFF/ON (stop/operate) button.
OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone.
(2) Select HEAT mode with Operation select button.
(3) Press Temperature buttonsTEMP
1. Cold air prevention control
When the compressor is not operating or is starting, and the temperature of indoor heat exchanger and/or the room tem-
perature is low or when defrosting is being done, the indoor fan will stop or rotate in Very Low speed.
2. High pressure protection
The compressor operational frequency is controlled by the temperature of the indoor heat exchanger to prevent the con-
densing pressure from increasing excessively.
When the temperature of indoor heat exchanger becomes too high, the high pressure protection works.
The indoor fan operates following the cold air prevention control. This mode continues until the temperature of indoor heat
exchanger falls.
3. Defrosting
Defrosting starts when the temperature of outdoor heat exchanger becomes too low.
The compressor stops once, the indoor/outdoor fans stop, the 4-way valve reverses, and the compressor re-starts.
This mode continues until the temperature of outdoor heat exchanger rises or the fixed time passes.
9-5. AUTO CHANGE OVER ∙∙∙ AUTO MODE OPERATION
Once desired temperature is set, unit operation is switched automatically between COOL and HEAT operation.
Mode selection
(1) Initial mode
When unit starts the operation with AUTO operation from OFF:
• If the room temperature is higher than the set temperature, operation starts in COOL mode.
• If the room temperature is equal to or lower than the set temperature, operation starts in HEAT mode.
(2) Mode change
COOL mode changes to HEAT mode when about 15 minutes have passed with the room temperature 1°C below the set
temperature.
HEAT mode changes to COOL mode when about 15 minutes have passed with the room temperature 1°C above the set
temperature.
NOTE 1
If 2 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 to the other operating mode (COOL ↔ HEAT) and becomes a state of standby.
Refer to NOTE 2 "FOR MULTI SYSTEM AIR CONDITIONER".
NOTE 2
FOR MULTI SYSTEM AIR CONDITIONER
OUTDOOR UNIT: MXZ series
Multi system air conditioner can connect 2 or more indoor units with 1 outdoor unit.
• When you try to operate 2 or more indoor units with 1 outdoor unit simultaneously, one for the cooling and the others for
heating, the operation mode of the indoor unit that operates first is selected. Other indoor units cannot operate, and
operation indicator lamp blinks as shown in the figure below. In this case, please set all the indoor units to the same
operation mode.
• When indoor unit starts the operation while the defrosting of outdoor unit is being done, it takes a few minutes (max. 10
minutes) to blow out the warm air.
• In the heating operation, though indoor unit is not operating, it may get warm or the sound of refrigerant flow may be
heard. It is not malfunction. The reason is that the refrigerant continuously flows into it.
OBH932
or button to select the desired temperature. The setting range is 10 - 31°C.
OPERATION INDICATOR
22
Lit
Blinking
Not lit