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catsoup
25-03-2017, 02:01 AM
Hi all,

I am trying to repair a domestic Electrolux fridge-freezer. Its spec is 74g of R600a.

After a de-icing "incident" a small 2mm leak was created resulting in the loss of the refrigerant. This was not noticed for about 24 hours. After which the fridge compartment was at about room temp, and the freezer was about zero centigrade.

I fully accept that the economic thing to do is to replace the whole unit, however as a project and a learning experience I am trying (as an amateur) to repair it.

This is what I have done so far:

I have repaired the hole in the evaporator. I a quite certain this fix is good.

I installed a bullet piercing valve onto the low pressure side of the compressor.

Then I used a single stage vacuum pump for 2 hours.

Then I weighed in the specified 74g of R600a. (Initially breaking the vacuum with the gas, then later running the unit's compressor to draw in the R600a). No air was able to get in.

Running the fridge-freezer showed that it could barely maintain -6 deg C in the freezing compartment, and the fridge remained at room temperature (or slightly above).

Suspecting that I had not done it correctly (loose hose or something), I did the process again. This time pulling a vacuum for 4 hours.

Same result. I did notice that with good ventilation to the condenser the freezer could get down to -7 deg C. But in the kitchen cabinet it could only reach +0.2 deg C. This was probably the same as before.

I had some advice from a qualified engineer who said the system is probably contaminated with oil from the compressor.

So, I have now circulated argon gas through the system. (No nitrogen available, but I have read that argon is okay?). The argon circulated freely and did not discharge any oil or anything else. I left it bubbling into a jar of water, which showed no signs of residue from oil or anything. I assume the capillary will reduce the flow so a mere bubbling rate is normal.

Since the argon "flush" discharged nothing, I am now thinking the compressor is faulty. The only indication I have of this is that I think that its now the most likely cause. Could the compressor have become damaged because it was left running for 24h following the leak? Also, I recall that the high pressure output pipe was very hot when testing the unit after the re-charge. Too hot to touch. That can't be okay? Does this also indicate a faulty compressor?

Any suggestions what could be the problem with this fridge-freezer? And how an amateur with limited equipment could get it going again?

Rob White
25-03-2017, 10:15 AM
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There are quite a few things wrong with what you have done.
Repairs need to be proved with a pressure test and a vac needs
to be measured with a vacuum gauge, not time. If it is leaking,
Vaccing for an hour or four hours will still result in contamination.

I would ask how you repaired the leak?

Brazing, without purging with OFN leads to risk of fire??

If you have not pressure tested the thing then you can't
be sure it is gas tight and when you vac it you can't be sure
it is vacced correctly.

If it was in a deep vac, you would suck in the 74g first go
So I think you need to check the repair.

Oh, by the way, you do know R600a is flammable don't you?

One other thing, we use OFN because it is proven to be dry,
as good as argon is I'm not sure of it's level of dryness and
it might be leaving residue behind?

Rob

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catsoup
25-03-2017, 10:25 PM
Hi Rob,

Thanks for the reply.

I don't have a very accurate vacuum gauge, but it did go to zero after about 15 mins. I left it on for a few hours to dry the system rather than expecting it to produce a significantly harder vacuum.

I should have pointed out, that after vacuuming it I left the pump off for 30 mins, and the gauge was still reading zero. So I am fairly certain that there are no leaks.

Also would it work for several hours if it had a leak? I thought it would progressively just get worse as the refrigerant leaked out? (By "work" I mean it consistently kept the freezer compartment at -7 deg C, with good ventilation to the condenser coils. )

I was thinking that the compressor may be faulty? (Valves burnt and leaky maybe after being run for 24h with no refrigerant?)

Thanks for pointing out about the risks of R600a. I am taking a lot of precautions!

Chris.

FaultCode
25-03-2017, 10:47 PM
How long have you left it running for to achieve your temperatures?

Weighing in a small charge can be tricky, yes you weighed out 74g from your gas cylinder, how much of that 74g remains in your charging hoses ?

Rob White
26-03-2017, 01:37 PM
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If you are certain you charged the correct weight, Faultcode makes a valid point,
Removing gauges does remove some refrigerant.

You only have one line tap valve (they are against the regulations for HC'c) and
I assume it is on the low side? What pressure was it running at on the gauge
While still connected?

With gauge on, switch off the comp, it will equalise through the capillary tube but slowly.
So when turned off, if the suction pressure instantly rises it could indicate the valves.

Sounds like the repair was good a vac standing test is a reasonable test method but
remember it is only one bar of pressure difference, a good pressure test would be a lot
higher.

If the repair is good and the charge is good, you are left with the comp. You purged it so it shouldn't be a blockage.

Rob

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