Daikin RZYQ7PY1 - Compressor Issue

[rude]

Hey Guys

Need a little help with this unit.

When I first looked at the unit the circuit breaker was tripped and would keep tripping even with no power on in the house.

So I replaced the circuit breaker.

After restarting the unit and put the unit on cooling the condenser fan starts, then compressor begins to ramp and unit starts drawing 1.5amps and then bang the circuit breaker trips.

It is a 3 phase unit incoming voltage is 240, 234, 234
I have measured the resistance on the compressor between each lug and i am getting 1.3ohms

I even megger tested the compressor to earth it is open.

The compressor felt quite hot I couldnt hold my hand on it otherwise it would have burnt me. I tried cooling it down but it didnt really make much difference and it still tripped.

This is where I am a bit stuck.

It sounds like the compressor starts to ramp and then after about 10secs it trips the breaker without high current or being down to earth.
The unit was apparently running fine all day and then tripped when we hit over 40c
My usual experiance with these is the board would usually fault and the unit wouldnt trip?

Anything else I need to check? Unit is approx 6 years old

Thanks

[frank]

An MCB will trip when it senses an imbalance as well as excess current.
Have you tried measuring the drawn current on all 3 legs up to the point it trips?

[install monkey]

had a few issues with daikin inverter comps, check inverter circuit, loose neutral conns, inv pcb, megger the pot to check resistance on each pin to earth with the comp lead unplugged, search for andys inverter guide (tayters guide)

[rude]

Thanks guys

I didn't take the amps from all 3 phases as it trips fairly quick. But at 1.5 amp on 1 phase I wouldn't think it would trip?

Im going to go back today with a Daikin inverter tester to check the board I'll see how I go with that.

[KAPINXO]

Hey mister.

I think you compressor have a low isolation. Check this with tester. I wish luck.

[rude]

Update!

I plugged in the inverter tester board is here is the result.

https://www.youtube.com/watch?v=mKszpOiGXcU

Looks like i may have a faulty board?
I will call daikin tomorrow and confirm.

[install monkey]

yep duff inv pcb, make sure u get heatsink paste with the new pcb, and clean the old stuff off too

[rude]

Another update.

I changed the inverter PCBoard ran the unit up and unit starting running compressor ramping up and drawing 8amps in about 30secs to a minute. Then bang the circuit breaker trips.

Before I started the the unit I checked the new board with the inverter analyser and got some random flashes. Which leads me to think I'm not testing it correctly or it's useless.

I megger tested the compressor again it all looks good. I would think it wouldn't run at all if it was buggered?

So I'm really back to square one. Not sure if I just wasted $700 on a new part or not.

Is there anything else I'm missing?

Indoor fan runs
Outdoor fan runs
Compressor starts and begins to ramp up then trips.

[rude]

The more I think about this the more i think its the compressor tripping the breaker down to earth.

Compressor runs, heats up, open winding and bang circuit breaker trips.

[rude]

So looks like I have fixed it.

Changed the circuit breaker again and the unit runs fine now.

Question: Why has this unit gone through 3 circuit breakers in 6 years. What could cause circuit breakers to keep failing?

[Brian_UK]

Cheap or incorrect circuit breakers.

Power supply fluctuations?

[rude]

Cheap or incorrect circuit breakers.

Power supply fluctuations?
Probably all of the above.

all that matters now is I have it working! And the unit has a new inverter board :)

[doorswing]

had a similar fault on a rzq100 meggered the compressor,all seemed ok .fitted new board,it ran for a short while then stopped.after three attempts it blew the board.i was told by a mitsubishi engineer on a vrv coure that a compressor can be down to earth at one spot,and will only show up at speed,i always change the compressor and board now as in the long run it is less expensive.
hope this helps doorswing.