Repairing an AC unit?

[T i m]

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

[Bob Minchin]

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?

[FMurtz]

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).

[tabbypurr]

though there are older ones that ran on R12 then in the 90s some intermedia tes.

NT

[T i m]

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

Understood.

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

[T i m]

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

[Bob Minchin]

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.

[T i m]

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

[Caecilius]

UV dye is often used for this. A google for "air conditioning uv dye" will turn up a few hits.

[T i m]

Yes, I already have some from when I did the car and it can work well, especially if that was the only leak and it was big enough to get enough of the dye in one place.

In the end we actually pinned the leak down with an electronic 'sniffer' and it was in the middle of the AC condenser / rad, caused by what looked like the remains of a big bug. ;-(

If I knew what sort of pressure these things run at I was wondering if I could just pump it up with air and see if it loses any pressure, before wasting refrigerant gas on it?

Cheers, T i m

[Caecilius]

I think you need to be careful not to introduce moisture, so compressed air is probably a bad idea.

I think air con shops pull a vaccum to get rid of old refrigerant and moisture. If you can get hold of a suitable vacuum pump, pulling a vacuum and seeing whether it holds might be a decent test for leaks.

[T i m]

Noted, thanks.

If there is a leak and you pull a vacuum, wouldn't you be dragging ordinary moisture carrying air into the system anyway?

As mentioned I have a garage owning mate who has an AC rig so that bit may not be a problem, *once* I have fitted the suitable 'car' AC port to the domestic AC unit?

Cheers, T i m

[Theo]

In places rather hotter than here, with rather less ready cash, pretty much any AC unit is refurbishable (likewise fridges). I don't know exactly what they do, but I assume it's similar kinds of regassing to cars - the people don't have any high technology or great training. They certainly aren't relying on factory gas, because some of these things are 40 years old. The piping is mostly copper so it's straightforward to braze. (however, the units might be a bit more heavy duty than ours, owing to having to work rather harder all day long)

If it's been condemned, and you have someone who has the kit and knows what to do (ie how not to vent the gas to atmosphere), what do you have to lose?

Theo

[Andrew]

The problem with hot and humid places is that the aluminium-based components like cooling fins on the evaporators, just rot away.

You need to spend some time in a coastal, tropical area to see how quickly stuff is affected by sun, rain and salt.

[whisky-dave]

There was something on the news about a nuclear power station reducing generating capacity as the water from the local river was warmner so could be used as effecintly to cool it down.

[T i m]

That was my thought Theo.

Quite.

Understood.

Nothing, hence the question here, but it was the 'means' by which I could get a mate with a std car re-gas rig to re-gas this potentially 'sealed' system for / with me?

I know he would be more than happy to hook his machine onto any std (car) AC coupling for me and do what needs to be done but how would get to that position?

Like, first I need to obtain a connector that matches his machine (breakers or aircon gas suppliers?) and then, assuming the broken system is already deplete of gas, fit a matching connector and ask him to re-gas it for me (or at let it run the diagnostics and see if it will be willing to)? Maybe the original filling point would be obvious (a sealed off pipe stub) and that would be the place to fit said connector?

So, I was looking for some practical pointers from someone who may actually know (from a personal experience POV) some aspects of all this?

Cheers, T i m

[T i m]

And that horse may have already bolted in any case? ;-(

Cheers, T i m

[T i m]

Understood.

I had exposure to one instance, an oil terminal on the coast somewhere (in the UK, I was there doing Datacomms stuff).

Because the site was so big they used to keep some very basic spec cars just sitting around that you could jump in and drive to another part of the site and leave the car there (for someone else to take).

I think they said they typically only lasted a couple of years before they rotted away, often with only a few thousand miles on the clock. ;-(

Out second hand Seahopper (folding boat) had been used in the sea and even the brass fittings were showing signs of corrosion (and it wasn't a boat you would typically leave afloat).

Cheers, T i m

[tabbypurr]

only some refrigerants are banned from release to the atmosphere. Butane & propane aren't.

NT

[T i m]

Interesting, thanks.

I'll check what gas my mate in the garage has on his auto AC service rig (OOI).

Cheers, T i m