compressor insulation

[kerrcell]

Hi Guys,

I came across a problem with regards to the insulation test of a compressor still connected to the plant charged with refrigerant .I once read that carrying an earth insulation test of a compressor can determine it's state or can predict an approx time for failure.This sytem uses R407c.

Any opinions to the subject.

[praveen]

Yes you can megger your compressor to see the earth faults if any..

[NoNickName]

An insulation test gives a GO/NOGO as a result. It can't predict the failure.

[Emmett]

You may not be able to predict the date of a failure but you certainly can tell a lot about your windings fitness by meggar, especially if you have a base line and or manufacturer specifications/recomendations. It will definetly tell you GO/NOGO.

[kerrcell]

I am with Emmett with his reasoning.Besides reading if there's a short of the windings or not ,can if a periodic log is kept know the health of the windings.
Dont't know but if a record is kept say every month or two and compare,then can read any difference in mohms if readings are different.Any views ?

[NoNickName]

That's impractical. How would you disconnect the compressor once per month and test it with the megger?
Also, subjecting the compressor to repeated 2.5kV stresses is not a good idea.
Also, megger readings are a diagnostics for ensuring the compressor is SAFE to use (rigid to respect to voltage), not a way to make sure is failproof. You are hijacking the meaning of the test.

[AUScooler:-)]

Safety insulation tests on some workplace sites are required at specified intervals some as low as 3 months apart which also requires records to be kept. Hermetically sealed compressors are classified as electrical equipment. This may not be the case in other countries.

[NoNickName]

Safety insulation tests are only required on electrical equipment and PSC (power and switchgear cabinets). I don't know in OZ, but in EU insulation tests are only required once, and then the equipment must be protected against short circuit, which effectively renders any further insulation test useless. In fact, you are not supposed to find any electrical equipment low on insulation if its protective devices are functional and not tripped.

[Quality]

PSC prospective short cirtcuit in UK is what its called ,call it what you want in you own feild but as you know BS7671 is a european standard

power switch cabinets >? did you make that up

[kerrcell]

Guys I came across this since at present am working for a company that has these scrolls feeding surfer rooms.A real sensitive area.Lately a compressor failed and created real havoc ! So I try all my best that through periodic testing of the insulation will carry such tests.I do not find any that will harm the winding.If I keep a log of these 8 industrial acs can get a rough guide of .I am reasoning same as AUScooler.But that's why am writing here for views and I respect all other as always.

[NoNickName]

No, I didn't. It's funny how britons only know BS norms and ignore EU updates.

[Quality]

No, I didn't. It's funny how britons only know BS norms and ignore EU updates.

What updates refering to PSC

[mad fridgie]

Are you actually tlking about winding I think you are actually talking about your dielectric strenth of your oil, over time oil can get contaminated and also chemically breakdown, this causes the electrical resistance

[Quality]

I agree with your post as I have experienced this many times in older systems . I call it running to death.
NNN has a habit of upsetting folk particulary when he is wrong

[AUScooler:-)]

Safety insulation tests are only required on electrical equipment and PSC (power and switchgear cabinets). I don't know in OZ, but in EU insulation tests are only required once, and then the equipment must be protected against short circuit, which effectively renders any further insulation test useless. In fact, you are not supposed to find any electrical equipment low on insulation if its protective devices are functional and not tripped.

A compressor can fail every single safety test a tech can throw at it, but still run without tripping all types of short circuit protection. It can be a workplace risk thats why customers pay big dollars so the test is not useless.

[NoNickName]

A compressor can fail every single safety test a tech can throw at it, but still run without tripping all types of short circuit protection. It can be a workplace risk thats why customers pay big dollars so the test is not useless.

That uniquely depends on the GO/NOGO criteria. And if a proper short circuit protection doesn't trip, than the compressor is not a risk to health or safety.

[NoNickName]

What updates refering to PSC

- Iec 61439-2: Power switchgear and controlgear Assemblies (Psc-Assemblies)

[Quality]

It was the cabinets bit that that made it daft but controlgear assy is more acceptable.

If ya don`t mind how do you separate/differentiate PSC for inspection and PSC for Power switchgear and controlgear Assemblies

[NoNickName]

I don't know what you mean.

[Quality]

I mean when refering to a job weather test the PSC or the PSC language may be our down fall I am not to sure how to type it

[Magoo]

Back to original question of testing windings.
I would prefer oil sample testing for acidity, which in turn gauges the potential failure of windings in a system.
Not too sure about all these currents oils, and if there are test kits available for them.

[NoNickName]

I mean when refering to a job weather test the PSC or the PSC language may be our down fall I am not to sure how to type it

want fries with that?

[Quality]

want fries with that?

good very good

[kerrcell]

What I've read may have been misinterpretated by some !A few years ago was on a course in a particular european country and one of the engineers suggested that through a megger(insulation) test,with refrigerant inside the system,one can draw certain conclusions on the health of the compressor/system,acidity.Don't know maybe someone has a better techical idea on this.I do not need to insulation test for any short circuit.Neither carry oil acid tests as the market ones we reach here are for the older ones,and the result is always a 100% acid when using a sampling pad with the newer refrigerants.