Mistsubishi Electric U9 Fault.

[CraigF]

Gents,

I have a site where a brand new puhz p125yha has been installed. 3 phase unit, supply on site is stepped down with a power perfector (you may well know which sites have these!!). Wired from the dis board in 4mm (15m cable run) evertuff. The unit ran fine on commissioning, no issues whatsoever. However after a month I am getting U9 fault. the unit will run the CFM for 2 secs and stop creating the fault.

I have gone down the usual line with Mitsi, who say categorically the supply voltage is not enough, at 391v.

The pink plug in the corner (Bussed DC, IIRC) is only reading 304vdc and needs 310vdc min for the fault not to appear.

I have been tasked with changing the cable as my superiors say the volt drop through the cable is causing this. I Have done some calcs that tell me I will only have 0.8% volt drop over this cable, which to me does not constitute a solution and we will be in the same boat after time spent on this. Personally I think 4mm is perfectly capable...

Any thoughts on this?

[CraigF]

To add more info, the standing inverter output to compressor is only 46v per leg, not the usual 90v min.

[JP6]

Sounds like you've answered your own question, There isn't enough voltage on each phase. Same problem is happening with single phase units and buildings trying to step down to 200V theses days. I can't see it being voltage drop from the cable, certainly not that much voltage drop! 4mm is pretty standard.

[CraigF]

JP, yes im exactly with you on that.

[cool hand fluke]

Just a quick one , I have had a u9 and mitsubishi advised a few things but kept faulting.
Turned out to be the reactor located behind the boards.
Bryan

[CraigF]

Ah ok, how did you measure/test this??

[cool hand fluke]

It's located behind the boards housing, to the left.
looks like a transformer, two red wires conected to it.
I did not test it, I noticed the connections were scorched.
Best ask mitsubishi how to test it.
But the code and and symptoms same.
I was advised u9 have 20 diff faults such as inverter and comp, power input or reactor.

[install monkey]

i had a reactor fail on a power inv on a pizza hut - bypassed it - the other 2 were ok, it ran for over 2 yrs because they would spend the money for repairs (75 quid each)- it had failed due to the sea air rusting

[CraigF]

Thanks again gents, back to site tomorrow, will post the outcome soon as!

[CraigF]

Went back to that unit today, switched it on and the f**ker ran with no issue... Scratching my head now seriously... How long till the call comes in again. Feels like i need some sort of voltage recording device to see if there's an issue with fluctuating voltage in the store.

[install monkey]

http://www.spcloggers.com/site/product/view-category/category-1/Three-Phase-Logger-SPC-Pro.html
get ur boss to put his hand in his pocket- think you can hire them;)

[JP6]

Have you got an A control service tool you can plug into the outdoor unit?? You can use the dipswitches to look at U9 latest error detail history.

[CraigF]

Blimey, a bag of sand!! Nice kit tho, unfortunately IM we been threatened with redundancy, so no money getting spent ATM, the joys of working with tesco...