Mitsubishi inverter problem

[R1976]

Hi,

Can you help?

Mitsubishi PUHY-P200YGM-A with a fault code 4225.

This is something to do with the inverter, I am told.

Checked voltage at 3 phase incoming terminals-all okay.

Checked all fuses.

Took leads off compressor and got balanced readings of about 21v when not running. Couldn't really check when it tried to run as it tripped too quickly.

In test run mode it did run for 10 mins and the comp ran for a few seconds on normal operation at the start of the day.

The inverter is seriously hard to get any measurements from, as it sits behind the control board. If you disconnect the leads it wont run-catch 22.

Mitsubishi wont help too much as they say its dangerous to check whilst live. With the way all the circuits are laid out, I agree. They said it might be easier to change the inverter pack but this will cost a fortune

Anyone any ideas or input?

[The Viking]

Inverter bus voltage less than 289VDC check the voltage at cn52c (240VAC)

Until Thermatech logs on, I guess the best advice is to check the above (it's from the handbook).

Also, in these circumstances it is always good practice to check the resistance across the windings and that they aren't down to earth.

Good luck.

[Thermatech]

Hello R1976

The fault code is related to very low or very high voltage in the dc part of the inverter.
Checking the incomming power supply was good, make sure no problem with N as any poor connection will show as voltage between earth & N & unballanced voltage on the 3 phases.
Did you get a voltage drop on the incomming power supply when the comp tried to start, poor terminal connections could cause voltage drop & 4225 fault. I had that ona system last year power supply had a floating N.

Any way you need to disconnect power leads from comp & measure resistance between windings & mega test each winding to ground to confirm comp motor ok. If the comp was locked we would expect to see overcurrent fault so expect comp is ok for the time being.
Then you need to find SW1 on the inverter board ( left side of inverter pack remove side panel of pack )
Turn SW number 1 to ON possition.
This makes inverter disregard most inverter faults for a limited time so you can test the inverter as stand alone not connected to anything.
Make the power cable to the comp safe ( 3ph can kill ) & power up.
Do the SW3 1&2 dips on the control board to make test run & measure the voltage supplied by the inverter to your made safe cable ends.
The voltage needs to be ballanced between each phase & earth. You can also check between phases as a double check.
Everybodies multi meter will read a different voltage reading depending on the specification of the meter so I cant give you an exact target voltage but it is likely to be around 180v a/c minimum.
This is the acid test to confirm correct operation of the complete inverter pack.

If it wont go then you have to trace through the components in the inverter pack on the incomming power & dc side of the inverter circuit.
1/Power supply noise filter
2/Diode stack ( rectifier to high voltage dc )
3/Contactor
4/Smoothing resistors & capacitors.
5/Fan control board.

You cant realy test these live but if you read up the manual you can do static test of the diode stack. Contactor resistors & capacitors are straight forward to static test.
It could be something very simple & cheap to fix.
If you have other units on site & you are brave then you can swap components to prove which need to be replaced.
Otherwise your into a new inverter pack & thats big money.

Dont forget to put SW1 no 1 on the inverter board back to off when you have finished otherwise you will have another problem.

Good luck

[R1976]

Compressor should be okay,as it ran for a while in test mode, great replies,

Thanks for the help!