Power Transistor Protection From Voltage Drop; Anomalous Power Transistor Current; Dewing Prevention Control; Refrigerant Quantity Shortage Protection - Mitsubishi Heavy Industries FDT100VNAWVH Service Manual

(g) Power transistor protection from voltage drop
Anomalous stop control
1) If the power transistor drops supply voltage, the protective switch in the power transistor operates to protect the
compressor and the power transistor.
2) Under any of the following condition, E41 is displayed and it enters the anomalous stop mode.
i) When the protective switch in the power transistor operates 5 times within 60 minutes and the compressor stops.
(h) Anomalous power transistor current
1) Prevents over-current on the inverter. If the current value in the power transistor exceeds the setting value, the
compressor stops.
2) If the current value in the power transistor exceeds the specified value and the compressor stops 4 times within 30
minutes, E42 is displayed on the remote control and it enters the anomalous stop mode.
(i) Anomalous inverter PCB
If the power transistor detects any anomaly for 15 minutes, including the stop of compressor, E51 is displayed on the
remote control and it enters the anomalous stop mode.
(j) Anti-frost control by the compressor frequency control
(i) If the indoor unit heat exchanger temperature (detected with Thi-R) exceeds the setting value at 4 minutes after the
start of compressor, the compressor speed (frequency) is controlled to initiate the anti-frost control of indoor unit
heat exchanger.
(ii) When there are 3 indoor unit heat exchanger temperatures (Thi-R), the lowest temperature is detected.
(iii) Regarding the anti-frost control by the operation stop, refer to the operation control function by the indoor unit
control and the cooling, dehumidifying frost prevention of page 21.
(k) Dewing prevention control
[Control condition] During cooling and dehumidifying operation, if all the following conditions are established, the
compressor speed (frequency) is reduced to prevent dewing and water splash.
➀ Cooling electronic expansion valve aperture (EEVC) is 500 pulses.
➁ Suction overheat is 10°C or higher.
③ Compressor speed (frequency) is 60 rps or higher.
[Control contents] ➀ When the suction overheat is 10°C or higher, the compressor speed (frequency) is reduced at each
➁ Compressor speed (frequency) does not rise till the cooling expansion valve becomes 460 pulses.
③ This control takes 60 rps as its lower limit so that compressor speed is not controlled when it is
(l)

Refrigerant quantity shortage protection

Under the compressor protection start III control during cooling and dehumidifying operations, the following control is
performed by detecting the indoor unit heat exchanger temperature (Thi-R) and the indoor unit return air temperature
(Thi-A).
[Control condition]
[Control contents]
Reduces compressor frequency
at each minute.
1 minute.
less than 60 rps.
When the state that the indoor unit heat exchanger temperature (Thi-R) does not become lower
than the indoor unit return air temperature (Thi-A) by 4°C or more continues for 1 minute.
It judges that the flowing of refrigerant in to the indoor unit is insufficient so that the compressor is
stopped and E57 is displayed on the remote control.
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Reset
Retention
1.5 3.5
Indoor unit heat exchanger temperature (°C)
47
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'19 • PAC-SM-309