Mitsubishi Electric CAHV-R450YA-HPB Service Manual page 157

[ X Troubleshooting ]
Inverter
-5- Inverter
Replace only the compressor if only the compressor is found to be defective. (Overcurrent will flow through the inverter if the
compressor is damaged, however, the power supply is automatically cut when overcurrent is detected, protecting the inverter
from damage. Make sure that the model selection switches on the outdoor unit (Dip switches SW4-1 through 4-6 on the out-
door unit control board) are set correctly.
Replace only the fan motor if only the fan motor is found to be defective. (Overcurrent will flow through the inverter if the fan
motor is damaged, however, the power supply is automatically cut when overcurrrent is detected, protecting the inverter from
damage.)
Replace the defective components if the inverter is found to be defective.
If both the compressor and the inverter are found to be defective, replace the defective component(s) of both devices.
(1) Inverter-related problems: Troubleshooting and remedies
1) Inside the inverter is a large capacity electrolytic capacitor, and the residual voltage that remains after the main power is turned
off presents a risk of electric shock. Before inspecting the inside of the control box, turn off the power, leave the unit turned
off for at least 10 minutes, and check that the voltage across CN-P and CN-N on the INV board has dropped to 20 VDC or
less. (It takes approximately 10 minutes to discharge electricity after the power is turned off.)
2) Perform the service after disconnecting the connectors on the Fan board (CNINV1 and CNINV2). Before plugging in or un-
plugging connectors, check that the outdoor unit fan is not rotating and that the voltage across CN-P and CN-N on the INV
board is 20 VDC or less. The capacitor may collect a charge and cause an electric shock when the outdoor unit fan rotates in
windy conditions. Refer to the wiring nameplate for details.
3) Reconnect the connectors on the Fan board (CNINV1 and CNINV2) after completion of maintenance work.
4) The IPM on the inverter becomes damaged if there are loose screws are connectors. If a problem occurs after replacing some
of the parts, mixed up wiring is often the cause of the problem. Check for proper connection of the wiring, screws, connectors,
and Faston terminals.
5) To avoid damage to the circuit board, do not connect or disconnect the inverter-related connectors with the main power turned
on.
6) Faston terminals have a locking function. Make sure the terminals are securely locked in place after insertion.
7) When the IPM or IGBT is replaced, apply a thin layer of heat radiation grease that is supplied evenly to these parts. Wipe off
any grease that may get on the wiring terminal to avoid terminal contact failure.
8) Faulty wiring to the compressor damages the compressor. Connect the wiring in the correct phase sequence.
9) When the power is turned on, the compressor is energized even while they are not operating. Before turning on the power,
disconnect all power supply wires from the compressor terminal block, and measure the insulation resistance of the compres-
sor. Check the compressor for a ground fault. If the insulation resistance is 1.0 Mohm or below, connect all power supply wires
to the compressor, and turn on the power to the outdoor unit. (The liquid refrigerant in the compressor will evaporate by en-
ergizing the compressor.)
HWE22020
Press the tab on the terminals to remove them.
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