Mitsubishi P120 User Manual

[ 

IX  Troubleshooting ] 

- 265 -

HWE09120

GB

The insulation resistance could go down to close to 1Mohm after installation or when the power is kept off for an extended 
period of time because of the accumulation of refrigerant in the compressor. If the earth leakage breaker is triggered, please 
use the following procedure to take care of this.

ŒDisconnect the wires from the compressor's terminal block.

ŒIf the resistance is less than 1 Mohm, switch on the power for the outdoor unit with the wires still disconnected.

ŒLeave the power on for at least 12 hours.

ŒCheck that the resistance has recovered to 1 Mohm or greater.

ŒFor easy on-site measurement of the earth leakage current, enable the filter with a measurement instrument that has filter 

functions as below, clamp all the power supply wires, and measure.
Recommended measurement instrument: CLAMP ON LEAK HiTESTER 3283 made by HIOKI E.E. CORPORATION

ŒWhen measuring one device alone, measure near the device's power supply terminal block.

Items to be checked

Phenomena

Remedy

[1]

Check the breaker capacity.

Use of a non-specified break-
er

Replace it with a specified breaker.

[2]

Perform Meg check between the 
terminals on the power terminal 
block TB1.

Zero to several ohm, or Meg 
failure

Check each part and wiring.
*Refer to (5) "Simple checking Procedures 
for individual components of main inverter 
circuit".

ŒIGBT module

ŒRush current protection resistor

ŒElectromagnetic relay

ŒDC reactor

[3]

Turn on the power again and 
check again.

1)

Main power breaker trip

2)

No remote control display

[4]

Turn on the outdoor unit and check 
that it operates normally.

1)

Operates normally without 
tripping the main breaker.

a) The wiring may have been short-circuit-

ed. Search for the wire that short-circuit-
ed, and repair it.

b) If item a) above is not the cause of the 

problem, refer to (2)-[1]-[6]. 

2)

Main power breaker trip

Items to be checked

Phenomena

Remedy

[1]

Check the earth leakage breaker 
capacity and the sensitivity cur-
rent.

Use of a non-specified earth 
leakage breaker

Replace with a regulation earth leakage 
breaker.

[2]

Check the resistance at the power 
supply terminal block with a meg-
ger.

Failure resistance value

Check each part and wiring.
*Refer to (5) "Simple checking Procedures 
for individual components of main inverter 
circuit".

ŒIGBT module

ŒRush current protection resistor

ŒElectromagnetic relay

ŒDC reactor

[3]

Disconnect the compressor wir-
ings and check the resistance of 
the compressor with a megger.

Failure compressor if the insu-
lating resistance value is not in 
specified range.
Failure when the insulating re-
sistance value is 1 Mohm or 
less.

Check that there is no liquid refrigerant in 
the compressor. If there is none, replace 
the compressor.

[4]

Disconnect the fan motor wirings 
and check the resistance of the fan 
motor with a megger.

Failure fan motor if the insulat-
ing resistance value is not in 
specified range.
Failure when the insulating re-
sistance value is 1 Mohm or 
less.

Replace the fan motor.

                                    [YJMU-A]