Mitsubishi Heavy Industries FDEN125VNXVD Service Manual Download

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'10 • PAC-SM-137

(l)

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.

Cooling electronic expansion valve aperture (

VC) is 500 pulses.

Suction overheat is 10°C or higher.

Compressor speed (frequency) is

rps or higher.

[Control contents]

When the suction overheat is 10°C or higher, the compressor speed (frequency) is reduced at each

1 minute.

Compressor speed (frequency) does not rise till the cooling

expansion valve becomes 460 pulses.

This control takes

rps as its lower limit so that compressor

speed is not controlled when it is less than

rps.

(m) 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 (Th

-R) and the indoor unit return air temperature

(Th

-A).

[Control condition]

When the state that the indoor unit heat exchanger temperature (Th

-R) does not become lower than

the indoor unit return air temperature (Th

-A) by 4°C or more continues for 1 minute.

[Control contents]

It judges that the ﬂowing of refrigerant in to the indoor unit is insufﬁcient so that the compressor is
stopped and

57 is displayed on the remote controller.

(n) Broken wire detection on temperature thermistor and low pressure sensor

Outdoor unit heat exchanger thermistor, outdoor air thermistor and low pressure sensor

If the following is detected for 5 second continuously within 2 minutes to 2 minutes and 20 seconds after the
compressor ON, the compressor stops. After a delay of 3 minutes, it restarts but, if the same is detected repeatedly 3
times within 40 minutes, the compressor stops with the anomalous stop.

Note (1) During defrosting and for 3 minutes after the end of defrosting, it is not detected.

• Outdoor unit heat exchanger thermistor: -50°C or lower
• Outdoor air temperature thermistor: -45 or lower
• Low pressure sensor: 0V or under or 4.0V or over

Discharge pipe temperature thermistor, suction pipe temperature thermistor

If the following is detected for 5 second continuously within 10 minutes to 10 minutes and 20 seconds after the
compressor ON, the compressor stops. After a delay of 3 minutes, it restarts but, if the same is detected repeatedly 3
times within 40 minutes, the compressor stops with the anomalous stop.

Note (1) During defrosting and for 3 minutes after the end of defrosting, it is not detected.

• Discharge pipe temperature thermistor: -10°C or lower
• Suction pipe temperature thermistor: -50 or lower

(o) Open phase protection (3-phase models only)

When 0V is detected on any of L1, L2 or L3 phase for 5 seconds continuously after the power ON, it judges the state of
open phase on the power supply and activates the anomalous stop (

34) 1 second later.

(p) Fan motor error

If the fan speed of 100rpm or under is detected for 30 second continuously under the outdoor unit fan control (with
the operation command of fan tap at

speed or higher), the compressor stops.

When the fan motor speed drops to 100rpm or under 5 times within 60 minutes and the compressor stops, it enters
the anomalous stop mode with

48 displayed on the remote controller.

(q) Anomalous stop by the compressor start stop

When it fails to shift to the compressor DC motor’s rotor position defection operation at 5 seconds after establishing
the compressor start condition, the compressor stops temporarily and restarts 3 minutes later.

If it fails to shift to the position detection operation again at second time, it judges the anomalous compressor start
and stops the compressor by the anomalous stop (

59).

Model

rps

~140