Trouble Treatment When The Main Power Breaker Is Tripped - Mitsubishi Electric PQHY-P72TYHMU-A Service Handbook

[ IX Troubleshooting ]
[THMU-A]

(3) Trouble treatment when the main power breaker is tripped.

Items to be checked
[1] Perform Meg check between the
terminals on the power terminal
block TB1.
[2] Turn on the power again and
check again.
[3] Turn on the heat source unit and
check that it operates normally.
(4) Trouble treatment when the main power earth leakage breaker is tripped
Items to be checked
[1] Check the earth leakage breaker
capacity and the sensitivity cur-
rent.
[2] Check the resistance at the power
supply terminal block with a meg-
ger.
[3] Disconnect the compressor wir-
ings and check the resistance of
the compressor with a megger.
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 heat source 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.
Earth leakage current measurement method
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.
HWE09080
Phenomena
Zero to several ohm, or Meg failure Check each part in the main inverter
1) Main power breaker trip
2) No remote control display
1) Operates normally without tripping
the main breaker.
2) Main power breaker trip
Phenomena
Use of a non-specified earth
leakage breaker
Failure resistance value
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.
- 331 -
Remedy
circuit.
*Refer to "Simple checking procedures
for individual components of main in-
verter circuit".
ŒIGBT module
ŒIPM
ŒRush current protection resistor
ŒElectromagnetic relay
ŒDC reactor
a) The wiring may have been short-
circuited. Search for the wire that
short-circuited, and repair it.
b) If item a) above is not the cause of
the problem, the compressor may
have a problem.
A compressor ground fault can be con-
sidered. Go to (2)-[2].
Remedy
Replace with a regulation earth leakage
breaker.
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
Check that there is no liquid refrigerant in
the compressor. If there is none, replace
the compressor.
GB