Mitsubishi Electric PQHY-P120THMU-A, Service Handbook

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[
IX
Troubleshooting ]
- 336 - HWE09080 GB
(3) Trouble treatment when the main power breaker is tripped
(4) Trouble treatment when the main power earth leakage breaker is tripped
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.
Œ
Disconnect the wires from the compressor's terminal block.
Œ
If the resistance is less than 1 Mohm, switch on the power for the heat source unit with the wires still disconnected.
Œ
Leave the power on for at least 12 hours.
Œ
Check that the resistance has recovered to 1 Mohm or greater.
Earth leakage current measurement method
Œ
For 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
Œ
When 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".
Œ
IGBT module
Œ
Rush current protection resistor
Œ
Electromagnetic relay
Œ
DC reactor
[3] Turn on the power again and
check again. 1) Main power breaker trip
2) No remote control display
[4] Turn on the heat source 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".
Œ
IGBT module
Œ
Rush current protection resistor
Œ
Electromagnetic relay
Œ
DC 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.
[YHMU-A]