R22 Mitsi City Multi problem

[markj]

hi,

Changed faulty comp on R22 city Multi 1999 unit windings o/s, re charged with correct amount of gas but on startup unit does it's pre checks comp starts but runs like a dog very lumpy with no real change to suction or discharge pressures after few mins goes out on Fualt Code for over current . So... i spoke to mitsi and checked each of the three phases and voltages were the same going to each leg of the comp then clamped each leg and the current was high at 40A approx on each leg. They recommended and concluded that the compressor was faulty so i repeated the whole process..... Same problem . Does any one have any ideas. If the invertor board was faulty then i would expect no o/p to the comp. :(

[RONB]

Have you checked the phases.Dose the Red go to T1 ,Yeliow T2 ,Blue to T3.I would check from the incomming mains to the unit and follow it all the way through to the comp.As it"s an old system you never knpw whats been done in the past.

[marc5180]

the compressor could be running backwards

[Jase]

Test the compressor/inverter side with an inverter analyzer as this will pinpoint you in the right direction!
I take it you didn't replace inverter boards. Am I correct?

Regards
Jase

[markj]

The incomming phase rotation has been checked and is correct. These units have phase reversal protection but i did check it just to make sure. With regards to the Invertor Analyser where can i get one of these and are they expensive. You are correct i didn't replace the inverter board, i had assumed that if the board had gone i would have no output( as previopus experiences have shown) But i may be wrong in this case, just don't want to change the board for no reason.

[puddleboy3]

Going to state the obvious after you added the refrigerant. Did you leave the crankcase heater energised! As from experiance these units can be a nightmare to get all the refrigerant in. You might want to look in the direction of the check valve on the discharge line as well! Hope this helps

[Jase]

I got the inverter analyzer from Daikin. Unsure as to the cost of it, but it is a good piece of kit especially when testing these inverters. Another thing to check is for tightness of electrics within unit.
Happy fault finding!

Jase:)

[puddleboy3]

I got the inverter analyzer from Daikin. Unsure as to the cost of it, but it is a good piece of kit especially when testing these inverters. Another thing to check is for tightness of electrics within unit.
Happy fault finding!

Jase:)

Jase I agree the Daikin Inverter checker is very handy(£65 less your discount).Only problem I could find was that it works a treat on VRV II as you can disconnect compressor and enter mode 2 setting 28 to force the inverter to output. On Daikin splits you put the unit in to fan only test mode. Daikin Sky air units you just run up as normal. Problem is on the old Mitsi PURY units there isnt such a test mode so the inverter sees that the compressor is disconnected due to not drawing any current and wont run long enough to let you know the inverter output is ok.

[Vee-Are-Vee]

Lumpy compressor could be one of the three TRM modules not switching correctly under load. Had the exact same problem with a 650 unit. Changed the pot and had the same problem afterwards, checked the TRM's, all were OK via diode test. Changed all three TRM's (and Diode stack as a precaution) and it worked like a charm.

The GateAmp board could also be sending incorrect firing information to the TRM's leading to lumpy running of the pot.

[laf100]

Mitsu always recommend changing the pot and inverter pack as a pair, the old comp could have taken out the inverter drive when it died. Just a word of warning to all, I have used the Daikin inverter tester, and it gave a clean bill of health (all LED's flickering at the same rate) to a an inverter that had a faulty TRM. Sometimes the inverter trouble only shows itself when under load.

If you are certain the inverter drive is OK, it is probably a sticky comp'. I had one last year that kept giving 4210 errors even after changing the pot and inverter, mitsu even sent another comp UG that did the same thing. I left the cc heater on for 48hrs and it eventually got away, it then gave 2 or 3 4210 errors over the next couple of weeks, but has been as good as gold since then. If you speak to a mitsu engineer (not tech support) they will tell you its a known problem with the A & B revision comps, apparantly revision c comps do not suffer the same probs, but mitsu UK will not officially recommed a C comp for an earlier CU, even though it is compatable.

[markj]

Hi, Finaly the customer gave he goahead for the additional works changed the inverter pack etc and all ok . Thanks for everyone help and comments.