Leak detection on a tiny system

I have a small wine fridge with a leak.

Background :
10 years ago my parents bought a cheap Chinese wine fridge. 6 years ago they asked me to look at it because it wasn't cooling. The discharge from the compressor gets routed through an Aluminium pipe that sits below the surface of the door gasket to prevent condensation. The insulation foam contains acid that eventually eats through the Aluminium tube, so I bypassed the tube and lopped about an inch and a half off the cap tube as it was plugged solid. Put a new oversized dryer on it and did a few nitrogen purge/vac cycles. Left it under vacuum for a day or so and it held at under 100 microns overnight, so I put 50g of r134a in it and called it good.

Fast forward 3 years and it's stretching its cycles out and not cooling as well, so I weighed the gas out to the best of my ability and it was well short. Vacced and put 50g of r134a in it as it was the start of the holiday season and they just needed it cold. Give it another 12 months and it is starting to go again, so they replace it and give it to me.

So, the thing holds 50g of r134a and I can charge it within a couple of grams using the gear I have. It appears to be losing 15-20g a year. My leak detector is pretty average with r134a but sensational with r22. To find the original leak I vacced it out (as well as I could given the magnitude of the leak) and put 10psi of r22 in it (static pressure). Backed that up with about 80psi of N2 and the leak detector went nuts as the r22 permeated the foam.

That was a big leak by comparison to what I have now.

So, I've found plenty of leaks before, but none this slow on a system this small. My thought was to do the R22 thing again (I think I calculated that works about at 2 or 3g of r22 in the approximate system volume), but wrap each assembly in cling film and leave it for a day, then poke the leak detector into the film to see if there is a residual buildup of gas.

I also though about 100psi of N2 and some big-blu, but I've struggled with that lately on really small leaks and there is a lot of pipework to check.

This is not critical, it's my own gear and I have plenty of time. I'm also willing to call it quits and recycle it should there be a leak in the aluminium evaporator or pipework. It's more an exercise in learning and if I happen to get a nice glass doored wine fridge out of it that is a bonus.

I brazed up a little transfer vessel to sit on my accurate scales so I can get the charge weight about right, but weighing out a charge that small with a standard recovery machine is a challenge. I do it by vacuuming out the transfer vessel and pipework, then packing the transfer vessel in ice and salt and using the temperature differential to suck out the gas. I can then weigh the end result and its within a couple of grams. If I were really serious I'd use dry ice, but I've only used that when pulling r22 out of burnouts without contaminating the recovery machine.

So, I'm after any old tradie tricks or other advice that might help cut down the hours I'm likely to put into this things.

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It is written somewhere in all the doc's I have what the minimum limit
is for a leak to be classed as a Leak (in the EU) I think it is 5 grammes
a year (I'm not 100% sure) so you have a small leak by any measures.

I know 144a molecular structure is smaller than that of 22 so it will leak
out slightly faster, but your leak detector picks up 22 better so I assume
it is an older HCFC one and not a newer HFC or HC detector.

So as to the leak, it is your fridge and it is your time, technically (in the EU)
you are breaking the law if you continue to recharge refrigerant into a system
that has a known leak.

But and this is a big but :D BUT you are losing less than 30g of refrigerant a year.
I do refrigerant handling assessments here in the UK and I have access to every
recovery machine that has been made and none of them can recover the last 50g to 100g
because the connecting pipe to the cylinder is always pressurised and that is lost.

On average we lose 50g an assessment so times that by 4 or 5 practices a day for 4 or 5
candidates and we lose about 1kg of refrigerant a month (a legal and accounted for).

So back to you, it is your fridge and your time, if you are happy to repair it you are wasting
about the same amount of refrigerant as 1 engineer doing 1 system recovery.

Not a hugh amount in the big scheme of things.

:)

Rob

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You can try this material.

http://www.dayan-rs.com/_Uploads/dbs...Files/9111.pdf

BradC,
There is a small chance it could leak from compressor electrical connections, might be worth eliminating.
As you get older that year comes around pretty quick, so chemi suggestion might be worth a go.

BradC,
There is a small chance it could leak from compressor electrical connections, might be worth eliminating.
As you get older that year comes around pretty quick, so chemi suggestion might be worth a go.

Thanks for the input guys. To be clear I have no intention of putting this fridge into service with a leak. I'm treating this more as a good learning experience where I have no time pressure or real need to get it fixed, so I won't be charging it back up unless I can be certain it's fixed.

I hadn't thought about the compressor feed-thrus. I'll add that to the list of things to check.

Yes, my leak detector is rated for HFC's, but it's a budget ion detector and despite what the documentation says, the sensitivity difference between HCFC & HFC appears to be one or more orders of magnitude. I've been saving for a better unit but real life keeps getting in the way (remember I don't do this for a living).

I've no experience with those chemical leak stop products. My gut says if they form a chemical plug to stop the leak, what are the chances of that leaking again at some time in the future. Additionally, how much would you put in a system that only holds 50g of refrigerant? The instructions say it travels with the refrigerant, so logic would say it must dilute the refrigerant to do that. That would reduce the refrigeration effect per mass flow, so reduce the efficiency of the system. The can holds 1.5oz (which google tells me is about 42g). It all starts to get a bit hard :)

Oddly enough I do a lot of specialised electronics repair. In the last 12 months I've pushed about 1.5kg of r134a into the atmosphere completely legally (freezer spray), which is 20 times the volume this fridge has leaked out over its entire life. Where practical I use butane or propane as a freezer, but sometimes when dealing with some circuits that have potential ignition sources I just have to revert to the expensive stuff. Sad that I can do that, but it's illegal for me to put it into a fridge. :(

Leaks can be easier to find with maximum pressure you can safely pump it up to.
I'm not sure what that is, guessing 1000kpa, maybe someone can advise with more definite figure?

Big blue is very good & some leaks can take 10 minutes to show up with very fine bubbles accumulating.

Your leak will be on the low pressure side.

Yeah, that's what I'm afraid of. A nasty aluminium evaporator with several aluminium-copper joints and enough pipe buried in the foam to make it a pig of a job. This thing was built to fail. Almost as bad as the torana heater core.

Many years ago, Kelvinater produced fridges using bundy tubing for refrigerant lines and it proved to get porous after a couple of years, it wasn't copper, it wasn't steel, and it corroded very easily, maybe you got something like this in your cabinet. Scrap it.

Quote:

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Originally Posted by BradC

Yeah, that's what I'm afraid of. A nasty aluminium evaporator with several aluminium-copper joints and enough pipe buried in the foam to make it a pig of a job. This thing was built to fail. Almost as bad as the torana heater core.

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It is ten years old :)

Fridges do well if they last 10 years.
As a commercial commodity this thing would
and has been written off and replaced, but as
a toy to play with, if you are happy to do it
then I see no reason why you should not.

Rob

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Rob

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G'day Rob. In my travels, i constantly hear the story of "my parents were given a fridge their parents owned for 20 or so years. Never had any problems so....Why is my 5 year old fridge needing repairs."

Short answer: Planned Obsolescence.:rolleyes:

Hi Mike,
I think it is called planned replacement after max ten years, manufactures go out of businees without sales. In our consumer society.
I still come across beer fridges in the garage from the 50's and sixties, still running copper pipe and large slow rev compressors. The only thing that fails is the thermostat usually a ranco bob basic. Seen some classics, latch buggered, door held in place with an old bike tyre tube
F&P sold their soul to China and now closed plant here, and i read Electrolux have shut shop in NSW as well after 70 years .

Quote:

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Originally Posted by mikeref

G'day Rob. In my travels, i constantly hear the story of "my parents were given a fridge their parents owned for 20 or so years. Never had any problems so....Why is my 5 year old fridge needing repairs."

Short answer: Planned Obsolescence.:rolleyes:

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I remember seeing an old hermetic rotor compressor that was built in the 1930's,
by Frigidaire. Just a small domestic pot, it was cut open and used as a demonstration
peace. The story behind it (if true) was that when it was designed and installed, after
about 6 years the range was pulled because they never failed. They lasted far in excess
of the fridge box itself and story goes well into the 1970's.

It might be just a really good story but there might be some truth in the fact that the
manufacturer pulled the design because they did not fail.

I am not old enough to remember the 30's (contrary to popular opinion) but I was working
on domestic fridges in the late 70's and early 80's and at that time we found that if a fridge
lasted more than 3 years it would go on and last forever. Rust and body work failing first.

Chest freezers being the best because they have fewer moving parts on them, but in general
if a fridge got to be older than 3 years they tended to last 10 maybe 15 years plus and
generally were only replaced because of cosmetic reasons.

I do believe we are in a more disposable society and we have a bit more disposable income
so fridges are just like TV's, washers and other commodities that are binned whether working
or not.

So if that is the case 10 years before obsolete is about right. I know some big AC manufacturers
who make it impossible to buy components for older models (5 / 6 years) or make replacement
parts so expensive it is cheaper to replace the whole thing.

Rob

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Quote:

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Originally Posted by Magoo

Hi Mike,
I think it is called planned replacement after max ten years, manufactures go out of businees without sales. In our consumer society.
I still come across beer fridges in the garage from the 50's and sixties, still running copper pipe and large slow rev compressors. The only thing that fails is the thermostat usually a ranco bob basic. Seen some classics, latch buggered, door held in place with an old bike tyre tube
F&P sold their soul to China and now closed plant here, and i read Electrolux have shut shop in NSW as well after 70 years .

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Hey there Neighbour. F and P sold out? News to me :(
They have a significant market in OZ. It's a shame one of the last original companies has thrown in the Towel to international pressure.

Honestly hope Sko**...New Zealand ain't giving up.. as their rival in Toowoomba Queensland shut their facility a few years ago. :off topic:

Responding to Rob. Post # 14.
Most insurance companies in OZ want nothing to do with claims on domestic items over 10 years old. Home and Contents Insurance barely covers anything to do with domestic Fridges and Freezers.

Those days of plugging in an OLD garage fridge for a Sunday arvo BBQ....or expecting an old rust eaten chest Freezer to store Xmas frozen items before the Summer Break.. are just memories.