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-   -   How to test compressor windings and grounding (http://forum.appliancepartspros.com/refrigerator-freezer-repair/522250-how-test-compressor-windings-grounding.html)

OlaS 04-10-2013 06:28 AM

How to test compressor windings and grounding
 
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Hello dear experts. I have similar issue than the one explained in the http://forum.appliancepartspros.com/...t-cooling.html thread.

The compressor keeps going on and off and the freezer is only getting to 32F.

So I am about to order the overload and relay kit for the model, here is my question though. The expert suggested to also test the compressor windings and grounding, but I am not sure I understand how to do so. I mean I know how to test Ohm, but I am not sure I understand where to find the windings and how to test the grounding as well.

If you can just point me in the right direction it would be greatly appreciated.

Attached the diagram of the Upper Unit Assembly with the compressor and other parts.

Thank you!

Ola

richappy 04-11-2013 02:26 AM

There is no evidence you have a compressor starting problem, but you might have a sticking control. Turn it up all the way and see if the freezer temperature gets lower.
You might also have an overheating compressor, if very hot, you might have a low refrigerant level, or a clogged condenser.

OlaS 04-11-2013 05:46 AM

Dear Richappy,

Thank you for your reply. all other causes were tested already, but thank you for listing them, that gives me confidence that we actually did the proper testing to identify the problem.

Here is what really happen - the compressor would not start after a power surge or my kid left the freezer door open, or both. The repairman came and replaced the relay with 3 in 1 HS810 relay. Since then the compressor behaves like I described. The technician said that it might be a faulty thermostat and suggested to order a new one. I started to have second thoughts about validity of the whole story and decided to educate myself.

What I have found is that the HS810 not only should not be used in my fridge but more importantly only can be used up to 1/5 HP. My compressor is at least 1/3 HP if not more - I have 30 QF big mama refrigerator.

Thinking that this relay and the built in run capacitor simply have not enough juice to power on the compressor for extended period of time to get it the freezer to freeze.

this is why the first thing I did is to order genuine parts for the refrigerator relay and overload + run capacitor (just in case, even though I think it is fine) and replace the 3 in 1 with the proper relay. If that does not work then we probably have the control board issue.

Thoughts?

richappy 04-11-2013 08:50 AM

I wrote an engineering report on the 3 n 1 and concluded it will burn out compressors on the ist power surge. They have also caused house fires. Best to put a 1000 joule surge protector in the wall outlet for this.

OlaS 04-11-2013 04:53 PM

Link to how to test the compressor winding - great!
 
For all folks reading this post here is the link to the post how to test compressor windings.

How to Test Refrigerator and Freezer Compressors

Also great site to educate yourself on appliance repairs.

richappy 04-12-2013 01:30 AM

That's not a good test procedure, hard to even get that kind of accuracy and repeatability in winding ohm test. The windings could be smoked and charred, but a ohmmeter with a 9 volt battery will show "normal" resistance.
Best way is with the proper start device and an amprobe, that will determine function and verify a partially shorted winding.

OlaS 04-12-2013 05:37 AM

Help me understand please
 
Rich and other Pros,

Here is what I am contemplating about.

If my 3 in 1 was able to start the compressor, even though the HP rating on the 3 in 1 was lower than the HP on the compressor, then why the compressor stopped after a short run.

In other words, can you please explain what what the HP rating is for on the start device? And what will happen if there is a HP mismatch between the start device and the compressor.

Thank you

Ola

richappy 04-12-2013 06:13 AM

The hp rating is set by the internal device overload trip point, the start capacitor may be a different value.
There are two major problems with these devices;
1) no thermal overload and the internal overload is not a crisp acting Klixon type
2) The start capacitor provides destructive overload currents to the start winding during power spikes.
This device will provide up to 60 amps of current during power transients. If the transients are close together, the rms power will exceed 6 kwatt! This level is a educated guess as power line inductance, proximity to the substation, use of surge protector, and other factors are involved.
Typically, both windings will explode open and put molten solder on the compressor motor frame, thus shorting it to ground.
This only applies to the modern, fractional hp R134A compressors as they are designed for high efficiency, but with no impedance protection.
I do not even recommend them for the old R12 compressors as they can cause house fires!

OlaS 04-12-2013 06:38 AM

Still did get the answer
 
Rich,

This is a 20 year old fridge - so the compressor is the old type and the original relay is a PTC type.

You answered a slightly different question than I asked.

Let's try again.

My compressor is 1/3 HP at least, the 3 in 1 rated at 1/5 HP.

I am going to replace it with the right one from the manufacturer, it is understood and I totally agree with you that the 3 in 1 should not be used at all or short periods of time. But this was not my question.

Assuming the compressor is good and there is no other issue, why the 3 in 1 was able to start it, and then why it caused it to stop after a short period of time and then what caused it to start again?

I am just curious to learn how the HP mismatch manifested itself in this situation.

Can you help?

Thank you,

Ola

richappy 04-12-2013 07:26 AM

The lower current trip out rating of the 3 n 1 you have will cause problems and trip out during normal operating currents, but this will be a short amount of time. You might have other problems in the fridg if it stops working. Voltage tests would confirm.


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