new compressor failure

[johnwayne]

I have a problem unit, FHP 070 geothermal has always dimmed the lights on startup finally burned out the compressor after 3 years. Installed new compressor, fliped the breaker and it burned out so fast the digital ampmeter never even registered, I mean the breaker tripped back out before my finger cleared it.
Put on another new compressor, ,same thing except it didn't ground and trip the breaker.
First time there was a possibility of slugging but absolutely not the second.
These are Copeland scroll compressors,are these not equiped with a thermal overload?
I'm somewhat new to ac compressors, but worked with pumps and motors for 40 years. Never saw anything burn out that fast in my life time.

Any ideas?

[The Viking]

Compressors in refrigeration circuits (a/c systems) rarely fails for no reason, the trick is to figure out why the first compressor failed.

How did you go about changing these pots?
Reclaimed refrigerant, changed compressor and drier whilst flushing the system with OFN, vacuum to 300 micron, recharged with virgin refrigerant. Those tasks and in that order?

Did you replace any electrical components?

Is this single or three phase?
Inverter driven or direct on line?



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[The Viking]

Oh,
One more thing, what refrigerant is it working on?

.

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[goshen]

Hi
lights dimming while comp starting points i a few directions
wrong sizing of cables
wrong method of starting-soft start vs direct on line
wrong connection of compressor-star vs delta
for a compresssor to burn out that fast ,you are probably doing something wrong.
i would recheck and have a qualified person have a look .
good luck

[install monkey]

dimming lights- my old r22 3.5kw fujitsu non inverter pulled 30amp on start up and that caused lights to flicker everytime the pot started- lasted 9yr now its been replaced for a 3.5kw inverter

[goshen]

Hi
diiming lights the way you discribe,usally meens wrong wiring sizing,
you can live with it but the lights will dim on startup.

[johnwayne]

I do not have nitrogen. other than that yes.
Direct on line. Other electrical checked out. R22. single phase

[monkey spanners]

One thing that springs to mind for killing the comp so quickly (they will usually hum for a while and cycle on klixon is wireed wrong...) is water from the ground loop, especially if you vacuumed it as it would pull even more in.

Did you weigh the original charge out etc?

[The Viking]

Well there are only so many things that would kill a compressor outright that fast.

-As MS said, water in the system
-Blockage of the system (discharge side)
-Faulty controls/electrics

If you have checked for moisture / water (standing vacuum is good for this), made sure there isn't any blockage in the system then the next thing to suspect is the start control for the compressor (capacitor / relay).
Not forgetting the obvious one, that the right voltage and neutral are present and correct even when the compressor is, trying to, run.

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[johnwayne]

No sign of water in the oil on the first compressor.
How do you check for blockage?