Mitsubishi Electric MSZ-A09RV-E1 Service Manual page 27

2. High pressure protection
In HEAT mode and manually-operated HEAT mode, the indoor coil thermistor detects the temperature at the indoor heat
exchanger and controls the compressor rotational frequency to prevent the condensing pressure from increasing
excessively.
3. Overload starting
When the room temperature thermistor reads 18°C or above, the compressor runs with its maximum frequency regulated for
3 minutes after the start-up.
4. Defrosting in HEAT mode
• conditions to start defrosting:
a) The defrost thermistor attached to the outdoor heat exchanger read -3°C or below.
b) The cumulative operation time of the compressor has reached any of the set values: 30, 40, 45, 55, 65, 75, 85, 95, 105,
115 minutes.
c) More than 5 minutes have passed since the start-up of the compressor.
When the above three conditions, a), b), and c), are satisfied, the defrosting starts.
wSet value of compressor operation time(hereinafter referred to as defrost interval)
The first defrost interval is 40 minutes long, and the second 45 minutes long.The third and subsequent intervals are set to
be longer, and less frequent, depending on defrosting time.
The third and subsequent defrost intervals follow any of the three patterns ... 5 or 10 minutes longer, the same, or 5 or 10
minutes shorter compared with the previous defrost interval ... with the longest 115 minutes and the shortest 30 minutes.
• Conditions to end defrosting
Defrosting is released when any of the following condition is satisfied:
a) The defrost thermistor reads 13°C or above.
b) Defrosting time has exceeded 10 minutes.
c) Some other mode than HEAT mode is set during defrosting.
Time chart of defrost in HEAT mode (reverse type)
vertical vanes
indoor fan
<outdoor unit>
Compressor normal
outdoor fan moter
Reversing valve
normal
VLo (temperature of indoor coil thermistor > 18:)
30
second
MAX Hz
1 30
second second
5 second
normal
ON
horizontal
STOP
100Hz
second
OFF
OFF
27
normal
normal
MAX Hz
30 1 1
second second
5
second
normal
ON