Repairing an AC unit?

I have previously helped a mate fix his domestic aircon unit but now (some years later) it's stopped working completely. They got an aircon engineer in who declared it as 'non repairable' so he's ordered a new unit.
I think he confirmed the issue being 'needing re gassing (because of a leak presumably) and it not being worth it.
Now, whilst I've examined / cleaned out a few different AC / fridge / cooler units and compressor pumps I've not even repaired or re-gassed anything so not sure what the deal is.
Like, I think I have seen these smaller / cheaper (~£650) units they seem to be 'factory gassed' and the pipe seal off, rather than re-gassable via a connector of some sort, as in most cars?
So, assuming this system was empty of gas, would it be possible to fit it with a car gassing point ... as my mate has a car AC re gassing unit?
Is the gas (or are the gasses) and lubricants used on cars the same as those in domestic units?
Obviously, if I could get it re-gassed I could use my mates sniffer to find any leak and potentially repair it (compressor seal?).
If I tried any of this it would mostly be for the S&G's but if it did turn out to be viable (from a d-i-y POV) I could actually make use of it here (It's one of those slimline wall mounted units with a concentric port (like a balanced flue) that goes though the wall, along with a small water drain pipe).
Cheers, T i m
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T i m wrote:

It all depends on what is wrong - sorry blindingly obvious statement! If it is just a leak in a pipe then it does rather depend on where and how accessible the pipe is whether it can be economically repaired. If the engineer has assessed it as having one actual leak but a whole load of potentially leaks in waiting due to corrosion say, then professionally he would be right to condemn it and fit new for a two visit definite fix. The compressor could be FUBAR and being a compact unit only the makers bespoke unit would fit in and that could be made of unobtainium.
Or the engineer is giving a Foxtrot Oscar response as he does not want to fix it and prefers only to fit new. Given the weather, he has possibly more work than he can cope with and this is the quickest fix for him?
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Bob Minchin wrote:

Depends on many things, one being the type of refrigerant I have two second hand split units which used R22. I gassed both with R290 (propane)both have been running successfully for five years since. I do have the equipment, compatible oil, (vac pump gauges etc).
Research hydrocarbon refrigerants.take the naysayers with a grain of salt.almost all the small fridges sold up to recently and coke and pepsi machines run on Butane, (R600a).
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On Monday, 6 August 2018 12:08:58 UTC+1, FMurtz wrote:

hey

though there are older ones that ran on R12 then in the 90s some intermedia tes.
NT
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<snip> >>> Obviously, if I could get it re-gassed I could use my mates sniffer to

Good result. And did you do anything else, other than the re-gassing?
Didn't I read that the supposedly 'better' gasses have smaller molecules so more likely to be lost via migration though the hoses etc?

Handy. ;-)

So, could these gasses all be used interchangeably for a given AC solution or are they typically designed (functionally) for one gas or another?
Would it be possible (conceptually) to fit a 'sealed' AC system with the port(s) used on typical car systems (eBay / breakers) and fill the system with the gas currently used in vehicle AC units or are they too different for some reason?
The idea is once re-gassed I can check for leaks (assuming it tests as ok in the first place)?
Cheers, T i m
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T i m wrote:

No I did not even replace the drier just held vacuum for longer (hydrocarbons are more forgiving of moisture)

If there is not provision you can silver solder one in the line

Yes but different testers sometimes (you can put stuff in refrigerant that shows up under ultra violet if there is a leak.

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wrote:
<snip> >> Good result. And did you do anything else, other than the re-gassing?

Ok, thanks.

<snip> >> Would it be possible (conceptually) to fit a 'sealed' AC system with

So, I'm guessing I would do so where it should be obvious it was gassed in the first place (I have the unit now but not had the time to strip it down to check for such things).
OOI, on my mates car a/c machine it has an interface that looks like a slightly bigger 'Euro' airline connector?
Cheers, T i m
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<snip> >Depends on many things, one being the type of refrigerant I have two

I have the old domestic AC unit now and apparently it takes 500ml of R-410A (Puron?) that I believe is an HFC and runs at a higher pressure than older systems (but what pressure)?
Mates car AC auto unit uses R-134A so whilst a different gas, would it be compatible? What would stop it being compatible?
Cheers, T i m
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On Sat, 11 Aug 2018 09:23:25 +0100 (GMT+01:00), Tim+

Yeah. I did look briefly at the list on Wiki but I'm no chemist so the nuances of each wasn't obvious.

Agreed.

Well, that's the thing. I wasn't sure if there were obviously technical reasons (pressures, chemicals affecting seals etc) over say simple cooling efficiencies.

And that's the thing. It's quite possible that my mates machine could take R-410A and a bottle of that could be much cheaper than buying a new AC unit, assuming we get a reasonable life out of one charge etc.
That may depend on what the fault is, or even if there is a fault at all. eg, I think some of the newer / ozone friendly gasses have smaller molecule sizes and can migrate through the hoses (not suggesting this is one etc).
Cheers, T i m
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T i m wrote:

The problem is that without a license or trade certificate most refrigerants are unobtainable but hydrocarbons are.

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wrote:
<snip> >> And that's the thing. It's quite possible that my mates machine could

Sorry, you have lost me there mate. Are you saying *I* can (probably?) buy 'hydrocarbon' gasses that will probably work in my a/c unit as a refrigerant (easier than the refrigerant that was originally in there)?
Is this a matter of 're-gas it with something that works, rather than the idea that could work better but would be more complicated (officially especially) to do?
I'm a complete a/c novice trying to get the bigger picture here. ;-)
Cheers, T i m
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T i m wrote:

If the UK is anything like here refrigeration is a closed family and anyone outside can not buy most refrigerants but anyone can buy hydrocarbons so if you want to DIY you are limited

Yes as non trade people are prohibited from using other than hydrocarbons

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wrote:
<snip> >> Sorry, you have lost me there mate. Are you saying *I* can (probably?)

Given my mate is in the garage trade I'm not sure yet if he might be able to access some gases under that role alone (him being 'Trade' rather than 'public', even though not in the aircon trade as such).

Ok (thanks) I'll have to look into what 'hydrocarbons' might replace what was in there originally and how I would get them into it.).
Maybe if it is already deplete of gas and I can fit a 'standard' port to it (if there is such a thing), a real a/c pro might then be willing to check it out for me?
At ~800 quid new I'd like to think it wasn't considered disposable? ;-(
Cheers, T i m
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A real pro will fit a port for you if necessary and gas it with the correct refrigerant - mine did. As it happened it was the same refrig as used in some car air-con.

--
bert

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<snip> >>Maybe if it is already deplete of gas and I can fit a 'standard' port

Can you remember how much that cost OOI?

Do you know if that was what was in there in the beginning or just that's what he used?
If it was as easy as that, I wonder why the guy they paid to come round and do just that, didn't? (I did ask mate if he could remember *why* hit wasn't repaired and I think he just said that the guy said 'it wasn't repairable ... eg it was a disposable unit?).
Cheers, T i m
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T i m wrote:

Something called R32 apparently is a replacement

Probably not although as an aside , A mixture of propane and isobutane is a replacement for 134a. the thing is in Australia and probably UK refrigerant gasses are controlled but hydrocarbon gasses in the main are not, one state tries to control them in air cons

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wrote:
<snip> >> I have the old domestic AC unit now and apparently it takes 500ml of

Ok ...

So are these 'CFC's' in the main?

Ok.
If I understand it correctly, the early gasses screw the ozone layer and whilst the later ones don't so much (?), they can be worse for global warming in general (and because some have smaller molecules, can permeate hoses and so leak easier)? ;-(
Cheers, T i m
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On Mon, 6 Aug 2018 11:13:53 +0100, Bob Minchin

;-)

Agreed, I suspect only likely in flexible hose (and it's couplings) or rigid pipe at a fatigue point or joint?

Understood.

Check.

Possibly, given it was a 'cheap' (as these things go) unit.

Again, perfectly possible and I'll further question my mate if he can remember exactly what the guy did and said.
Cheers, T i m
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T i m wrote:

A vast proportion of the pipe will be surrounded by fins and folded back on itself. If this has failed with a pinhole, the replacemetn might well also be unobtainable.
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On Mon, 6 Aug 2018 19:23:26 +0100, Bob Minchin

True, but might it be repairable?
If the pipe was copper and it was just a pinhole in one place, couldn't the fins be moved away in that location and the hole say soldered over?
Or if ally, the hole covered with a metal epoxy?
As I said, I think the first task (after getting the unit) would be seeing if it was possible to gas up somehow and then look to see where any leaks were. Obviously, if there were any obvious signs of corrosion in 'bad places' I may not bother with the re-gassing.
If I could inject 'a' gas (like town gas or acetylene) somehow that could be mechanically sniffed, that might be easier as long as it didn't affect anything negatively?
Cheers, T i m
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