Fujitsu VRF II inverter compressor lock

[joonis]

Hi, everyone

Unit consists of 1 inverter compressor, and 2 on/off compressors, client used to hire another company (fujitsu dealers in my country fml), they have changed 9 compressors in ~2 years.

Compressor makes a ticking sound for few seconds, but doesn't start up. Replaced inverter board, but that didn't help either.

We took refrigerant samples and in the lab we found that there was a lot of non condensibles (air) in the system, piping diameters and lenght are ok, so we pumped down the refrigerant, changed a compressor,, filled system with nitrogen, vacuumed and put a fresh r410A in the system, all according to unit needs and pipe lenghts after a few days and tried the new baby.
Compressor worked well... for a minute. Then same symptoms happened. we checked pipes for clogging, everything seems to be fine.

Masters, any ideas why did the compressor was locked again after ~1 minute of work?

[Greek_engineer]

how about checking the power and Hertz?

[RusBuka]

Ahaha, I dont understand how they can kill twin rotor invertor)))
You need to clean all pipes from oil.
Next you need find someone with Service Tool, and find why they dead.
High discharge temperature and injection i think.
Someone fiil pipes with nitrogen anothers open valves without vacuumation)

[Tayters]

Hi,

Compressor configuration like that would be V series. VII used one inverter and one fixed speed unless your region had something special?

Inverter circuit needs testing as already said, any fault codes, something broken up and getting sucked into compressor. Do fixed speeds run when contactor pressed in (if V series then plenty of compressor issues in the early days esp with master and slave setup), power and connections through noise filter, IPM boards, capacitors and external resistors alright, cables to compressors, main supply and neutral.
Has Fujitsu looked at it or just an AC contractor?

If compressor is locked again that quick then you need to chop it open and see what has got sucked inside. Perhaps check the one you've taken out first and make sure customer has a fat wallet which they don't mind emptying, good luck!

Andy.

[Tycho]

Never mind, thought it was something else, sorry

[RusBuka]

Airstage V dont check of alternation of phases.
If have confused with power supply or have confused with wires to the compressor after the IPM - compressor will jam.

[joonis]

As i said, fujitsu in our country are not really the best people to ask for help. They have been here lots of times, and they have changed 9(!!!) compressors in a year. And thats it they didnt offer any explaination for user or anything.

On the electric side everything seems to be ok, tested ipm board on another unit, works fine.
We cut open compressor, doesn't seem tragic, just some copper dust, although not much.
Could even a small amount of debris cause this?
Is it possible that power module sometimes switch phases and as RusBuka said - jam a compressor?