winding burnt - embraco

[clime.auto]

Hello,
Could someone tell what happened with this new embraco compressor? it has been fitted on an air drier.
Thank you
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[The Viking]

Well that the windings overheated, most likely due to a short, is quite obvious.

The big question is why.

Accidic oil due to poor workmanship at installation?
Mechanical failure?
Incorrect power supply?
Too high discharge pressure?
Too high discharge temperature?
Not enough cold refrigerant returning to the compressor?

Sorry, impossible to tell just from looking at pictures I'm afraid.

[clime.auto]

The compressor is NJ6220Z (displacement 26 ccm).
This is what I know:
- mechanical is ok
- the installer put 275g refrigerant
- no oil missing (750ml)
- oil was black
- no parameters were checked after installation of the new compressor

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[chemi-cool]

Wrong electrical connection. Part of the start winding is burnt.

[Glenn Moore]

Hi clime-auto
This is a very strange looking burn out. Part of the start winding and part of the run winding has burnt out. The other parts look as new. This may be a case of the internal motor connections being connected wrongly. ie a manufacturing error.
I would send this back to the manufacturer for a full examination and report

[chemi-cool]

Hi clime-auto
This is a very strange looking burn out. Part of the start winding and part of the run winding has burnt out. The other parts look as new. This may be a case of the internal motor connections being connected wrongly. ie a manufacturing error.
I would send this back to the manufacturer for a full examination and report

Glenn,
Each compressor is tested after assembly.
Start winding is connected to run winding so that is the reason the run winding is burnt.
We don't know for how long it was switched on.

[frank]

Was the refrigerant R407C by any chance?

[chemi-cool]

Was the refrigerant R407C by any chance?

Something you want to share with us frank?

[frank]

Hi Chemi
I've seen it many times with black oil...like treacle sometimes.
It's a mixture of R407C, POE and moisture in the system.
All points to a lack of good evacuation procedures at the time of installation.

[clime.auto]

it was charged with R134A (275g)

[mikeref]

Was 275 Grams of R134a the full gas charge? Compressor seems over sized for that small amount.
2 door bottle chillers use a 14 CC compressor, along with 400 to 450 Grams of R134a.

My point is: a 26 CC compressor couldn't possibly function with a 22 PSI suction pressure on only 275 Grams.

[Glenn Moore]

Hi Frank
I did the warranties on Maneurop recips for 6 years and experienced many what we deemed as "Black Oil Syndrome " compressors. Some were on R407C but many more were on low temperature R404A machines. We found unless the system was thoroughly cleaned by removing as much of the old Black Oil and fitting a Pure molecular sieve type drier, evacuating etc, further failures with Black oil of the replacement compressors would occur.
From a lot of tests it was found that the additives in the POE lubricant to improve the oils ability to withstand High bearing loads , high temperatures etc could be extracted by some types of filter drier dessicants. So we had both pure 100% molecular sieve driers made , and also mixture type driers, which were made with Molecular sieve, silica gel ,and activated oxides.
So with new systems we used pure Molecular sieve driers as they have excellent drying ability but also left the additives in the lubricant to permeate into the granular structure of the bearing surfaces. After some weeks the additives had done their job and during normal service work a mixture type drier could be used safely.
Activated oxides are good for acid retention, but as there is no acid in a new system the acid adsorbing element is wasted , but over time weak acids will appear when the mixture type of drier will become beneficial to the system especially after service work.
I was involved in sorting out 2 multi compressor failure sites with Black Oil and many other sites to reduce the failure rates .
But I never had any motor burn outs with back oil only massive piston gudgeon pin wear and con rod small end wear resulting in the compressors still running but unable to pump or compress.
But the burn out in the Embraco machine is only on part of the start winding and part of the run winding which to me seems as if the motor windings on one side were never energised and all current was sent through only half the motor . I don't believe this is a black oil job but this is the first motor ive seen in that condition Id be interested in your comments Kr Glenn

[mikeref]

Glenn. i'm not in a position to dispute your experience.

Why this compressor burnt in that manner could be determined by the original installer's monitoring after the power was switched on. We all know initial start up of a compressor has to comply with Manufacturers specifications after the suction pressure stabilises...but we are moving just..( OP's quote ) .. point 275 kilos of R134a.

Seems to me this air-drier was way undercharged and the compressor was short cycling on a vacuum.
Best regards to all. Mike.

[Glenn Moore]

Hi Mike
Your possibly right in what caused the compressor to cook , but its the way the windings have only burnt on the one side is unusual . With single phase machines you have 2 windings ie Start and Run . These are wired to a common point so if the motor was overloaded the complete start winding would have cooked if the machine could not start to rotate. If the machine was running in an overloaded state the klixon should have protected the run winding . Its my inquisitive nature I like to fully investigate all failures conclusively.
Believe me manufacturers can make mistakes just as much as us engineers, but we often get lumbered with the mess to sort out
Kind regards Glenn

[mikeref]

Glenn. You are right. I wasn't paying attention to the abnormal manner this dome shorted out.