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no thermal protection for refrigerator compressor -- fire hazard?

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no thermal protection for refrigerator compressor -- fire hazard? Matt 05-01-2007
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Posted by Matt on May 1, 2007, 9:28 pm


Hi folks--

I have a little (about 1.5 cu. ft.) refrigerator that died---doesn't
cool and makes no sound.

There is a kind of circuit breaker inside the "relay assembly". That
breaker butts up against the compressor, and apparently it is supposed
to sense overheating of the compressor. The breaker can be removed from
the rest of the relay assembly. It makes a rattling sound when I shake
it. When I bypass that breaker, the fridge seems to work fine.

Is that breaker designed for fire safety or just to protect the
compressor from overheating?

I don't mind risking the compressor being ruined or the whole fridge
being ruined since I got it for free.

Of course I wouldn't want to risk burning the house down.

Would I be risking a fire if I remove that breaker and use the fridge?

Thanks for your help!

Matt

Posted by Mark on May 2, 2007, 1:45 pm



> Is that breaker designed for fire safety or just to protect the
> compressor from overheating?
>
>

It's probably the overload protector...if the power goes off and then
back on after a second or two, the compressor has to re-start against
the built up pressure and it can't.

so that device is designed to click off for a while until the pressure
dies down and it can re-start.

You should be able to find a replacement for it.

I would do that if I were you otherwise the compressor will probably
be runied one day when it tries to re-start.


Mark





Posted by Matt on May 2, 2007, 4:23 pm


Mark, thanks for your reply.

Mark wrote:
>> Is that breaker designed for fire safety or just to protect the
>> compressor from overheating?
>>
>>
>
> It's probably the overload protector...if the power goes off and then
> back on after a second or two, the compressor has to re-start against
> the built up pressure and it can't.
>
> so that device is designed to click off for a while until the pressure
> dies down and it can re-start.
>

I see ... now I find a datasheet for the device at:
http://www.sensata.com/files/4tm.pdf

> You should be able to find a replacement for it.
>

I found it at jr.partsearch.com for $22 delivered. It seems that a
fridge of this size goes for around $80-$100 new.

> I would do that if I were you otherwise the compressor will probably
> be runied one day when it tries to re-start.

I drilled open the overload protector and found a dry dead roly-poly
centipede and something that looked like a worm that was still wet.
Also the (coil) heater was fused and melted into pieces. My guess is
that the bug blocked the contacts from tripping off so that the heater
overheated and fused. From the datasheet:

> The fundamental actuation
> principle incorporates a noncurrent
> carrying snap-acting disc,
> which is located above the heater
> element. (REFER TO BACK PAGE
> FOR REFERENCE DRAWINGS).
> In addition to radiant heat generated
> from the heater, compressor shell,
> and ambient, the disc senses the
> heat from the metal pin carrying line
> current through the hermetic terminals.
> When the disc snaps, it actuates the
> spring arm located above the disc,
> opening the contact circuit - which
> shuts off the compressor motor.

My last question is whether it is common for the protector to trip or
whether the fact that it tripped (or tried to) indicates another problem.

Matt

Posted by Mark on May 3, 2007, 2:32 pm



>
> My last question is whether it is common for the protector to trip or
> whether the fact that it tripped (or tried to) indicates another problem.
>
> Matt

It is very common for it to trip if power is removed from a running
compressor and then re-applied without waiting a few minutes for the
pressure to equalize.

If you reapply power before the pressure equlaizes, the compressor
motor cannot start so the motor will be powered and not turning and it
draws an excessive current that will burn it out in a handfull of
seconds. The protection device is designed to open the circuit in a
second or two.

The protection device will cool and reset itself automatically after a
minute or two.

Almost every refirgerator and air conditioner works this way.

Caution, do not drill into the compressor, it is hermetically sealed.

If you found a replacment protection device, buy it, replace it and
consider that you have done a great job.

Before you buy a new replacement protection device you can bypass the
old protection device just for a short test and verify that the
compressor works etc. but DO NOT use the unit that way. Do not remove
and re-apply power without the protection device in place.


Mark




Posted by Matt on May 3, 2007, 7:10 pm


Mark wrote:
>> My last question is whether it is common for the protector to trip or
>> whether the fact that it tripped (or tried to) indicates another problem.
>>
>> Matt
>
> It is very common for it to trip if power is removed from a running
> compressor and then re-applied without waiting a few minutes for the
> pressure to equalize.
>
> If you reapply power before the pressure equlaizes, the compressor
> motor cannot start so the motor will be powered and not turning and it
> draws an excessive current that will burn it out in a handfull of
> seconds. The protection device is designed to open the circuit in a
> second or two.
>
> The protection device will cool and reset itself automatically after a
> minute or two.
>
> Almost every refirgerator and air conditioner works this way.
>
> Caution, do not drill into the compressor, it is hermetically sealed.
>

I only drilled some plastic rivets out of the protection device so as to
open it for a post-mortem. The rattling sounds I mentioned were
fragments of the fused heater.

> If you found a replacment protection device, buy it, replace it and
> consider that you have done a great job.
>

Okay, I just ordered the replacement part. By the way, I picked up the
fridge at somebody's curb on junk day. It is five years old and hardly
a scratch on it. This will keep it out of the landfill for a while.
Hmmm ... now if I can figure out how to keep a roly poly from crawling
into the new part ...

> Before you buy a new replacement protection device you can bypass the
> old protection device just for a short test and verify that the
> compressor works etc. but DO NOT use the unit that way. Do not remove
> and re-apply power without the protection device in place.
>
>
> Mark

Thanks for your very detailed and helpful replies.

Matt

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