Mitsubishi Electric PEFV-P72NMHSU-E Technical & Service Manual page 55

Check items
[3] (1) Turn off the breaker.
Check for
inverter
damage.
(loaded)
(2) Turn on the breaker.
(3) Operate the indoor
units.
[4] Disconnect the indoor unit fan
Check the motor wiring, and check the
fan motor resistance and the wire-
for a ground wound resistance of the fan
fault and motor.
check the
coil for
problems.
3. Troubleshooting when the main power breaker trips
Check items
[1] Check the resistance between the
terminals of power supply terminal
block TB2 with an ohmmeter.
[2] Turn the power back on and check
again.
[3] Check the indoor unit for normal
operation.
HWE1017B
Symptoms
1) The units stop within 10 sec-
onds of startup, and a posi-
tion detection error or an
overcurrent error is detect-
ed.
Error code:4255
2) An overcurrent error is de-
tected after approximately
10 seconds of operation.
Error code:4255
3) Overcurrent error due to
short-circuited motor
Error code:4255
4) A line voltage imbalance ex-
ceeds the greater of the fol-
lowing after the rotation
speed has been stabilized:
5% or 5V.
1) Insulation resistance failure
of the fan motor
Insulation resistance of be-
low 1 MΩ is considered ab-
normal.
2) Broken fan motor wire
Reference value: Normal
wirewound resistance is
several ohms.
(Varies with the tempera-
ture)
Symptoms
1) 0 to several ohms, or insula-
tion resistance failure
1) Main power breaker is tripped.
2) Nothing appears on the re-
mote controller.
1) The indoor unit operates nor-
mally without tripping the main
breaker.
2) Main power breaker is tripped. The fan motor may have had a ground
- 49 - 49
Actions to take
Check to see if the fan motor is locked.
Replace the fan motor if it is locked.
If the problem persists after replacing
the fan motor, replace the INV board.
If the fan motor is not locked, go to item
[4].
If no problems were found with item [4],
replace the INV board.
If the problem persists after replacing
the INV board, replace the fan motor.
a)Replace the INV board.
b)If the problem persists after replacing
the INV board, replace the fan motor.
a)If no problems were found with items
[1] and [2], check for short-circuited mo-
tor wiring.
b)If no problems were found with item a),
replace the fan motor.
c)If the problem persists after replacing
the fan motor, replace the INV board.
a)If a voltage imbalance is detected, go to
item [4].
b)If no problems were found with item [4],
replace the INV board.
c)If the problem persists after replacing
the INV board, replace the fan motor.
Replace the fan motor.
Replace the fan motor.
Actions to take
Check the components in the main invert-
er circuit.
*Refer to "4. Simple check on the main in-
verter circuit components".(page 50)
a) Diode bridge
b) Inrush current limiting resistor
c) AC reactor (ACL)
d) Current sensor (ACCT)
a) Look for a possible short-circuit, and if
found, repair.
b) If no problems are found with item "a)"
there may be problems with the fan
motor.
fault. See section 2.-[1].
GB