View Full Version : Retrofitting an R12 system to R134a

23-05-2014, 04:40 PM
I have been doing a job for a customer and the compressor wouldn't start, found one of the capacitors to be faulty so looked into replacing...by which time he had already got one and fit it himself. I warned him before hand that the compressor had no oil in it but if I could get it to run I could isolate the refrigerant and put fresh oil in, because he didn't wait he ran it and has seized the compressor.

I told him to look at getting the compressor reconditioned and that I could isolate the pipe work so the only gas lost would be what is in the compressor and once reconditioned it could be re piped and run. After giving him a price hes again taken it into his own hands to source another compressor with synthetic oil in and to retrofit the unit to R134a on the advice of his previous engineer.

I have no previous experience of carrying out a retrofit and was just wondering how you go about getting all the oil out of the system? I know the expansion valve wants replacing and the drier would've been replaced either way but unsure on exactly how you flush the system?

I have read that you should clean out as much as possible from compressor, (which will be all now the compressor is getting swapped out) and then to run unit for 24 hours and remove oil from the compressor and then repeat the process after refilling with new oil.

My main concern is how you clear it from places such as receiver etc, the last thing I want to do is fit everything and ruin the system because everything hasn't been cleared out thoroughly.

The unit is a cellar cooler, prestcold condenser with a searl evaporator and the compressor is a semi hermetic prescold compressor which originally used to run R12 but has been swapped cant remember what gas he said it had been swapped to think he said R49 but may be wrong.

monkey spanners
23-05-2014, 06:21 PM
Run the new compressor on R49 (R437A) as well, the gas is mostly R134a with some propane in to help bring the mineral oil back so will work fine with ester oil.

Where had the oil gone from the old compressor?

I have done hundreds to R12 to R134a conversions, it is not difficult but can be a bit time consuming.

Customer sounds like a tit.

23-05-2014, 07:58 PM
I don't know where the oil has gone, the unit has a note in marker on one of the panels saying the compressor was low on oil dated 1991. Im guessing that it hasn't been running like that for all that time and perhaps has been decommissioned a while and reinstalled recently. The guy told me its only been in 18 months, to be honest I don't know much about the history of the unit because neither does he.

Think its a case of buying it because it was cheap and not bothering to find out the history etc of the unit, although whoever installed it should have checked the oil levels really before it was commissioned. So it could be that it was short from day 1 of install and finally run itself dry.

In terms of actually flushing the system is that the correct process then? I assumed you needed to flush the pipework through with like nitrogen or something else to force the oil through the system. I have also seen Retrofit kits but wasn't sure if they were for more industrial style equipment.

I think putting R49 may be the best option then....my biggest concern was the oil not getting back properly and causing a blockage, but if R49 will bring it back as well as run with ester oil then it could be the best option.

Just means I have to shell out for a full bottle.

Ha ha ha he's not too bad to be honest, just one of them customers who cant just pay you to do your job and leave you to sort things properly...too busy thinking about saving money.

monkey spanners
23-05-2014, 11:40 PM
The other option is to run it on R134a for a few hours or a day, then change the oil again, then maybe a week or so and change again. It is not an exact science.

Mostly we would do three oil changes with ester oil, then a final one when we change the R12 for R134a.
A few times we did it backards when the R12 had leaked out.

Can you not run it on the R49/R437A thats in it now? It works well with either mineral or ester oil.

24-05-2014, 07:57 AM
I would be tempted to walk away from this one mate. How can you guarantee the work you are doing when this guy is constantly meddling with the system himself. Had customers like this in the past, who want to do it all themselves and just call you when they find a bit they can't do, or they've broken it! Generally not worth the hassle...

24-05-2014, 11:20 AM
I'm not 100% on it being r49 I've tried contacting him again to find out but can't get in contact. Something in the back of my mind is saying rs24 which is also a replacement for r12....I've just done a check and the make up of the two is very similar, although r49 looks like the best choice if I had to buy a bottle myself. I have looked at another job for a customer who has an old r12 unit which the compressor has seized, by the looks due to running bone dry because they don't have a service contract with anyone.... that's running r409a but reading up on r49 it's meant to be a better replacement for r409. If was to get that job also I could probably justify paying for a bottle, but abit steep for one job.

To be honest Newmanref I had considered it when he'd told me what he'd done fitting the capacitor himself because I knew what the out come was before I looked. It's hard to walk away from a job before it's fixed without feeling a bit bad even though the systems in that state because they can't just leave it to the engineer to sort it.

I honestly don't see the point in calling an engineer out if they don't listen to what he has to say, the job originally could've probably been fixed for around 100 but bet he's spent at least three times that just to replace the compressor and still owes me for labour costs etc....just goes to show that trying to save money by doing it yourself can seriously impact on the price.

25-05-2014, 09:46 AM
Right, he's finally got back to me and he says the other engineer who fit the unit says its on R42d. ive told him that as far as im aware that gas doesn't exist and are you sure its not R422d. I thought R422d was a replacement for R22 systems not R12, ive looked into what oil it should run on and I think the stated is mineral but seen a couple of posts on here saying it works best with POE as they have had problems with the mineral oil returning to the compressor and it sitting in the receiver....perhaps this could explain what has happened to the oil from the compressor??

He's just got back to me now and says 'that might be it' for the refrigerant...do you think im best to just cutting my losses and walking away? I feel a bit bad leaving him with no running unit but on the other hand I don't want the consequences that could come with the unit failing because the information im getting about the unit isn't exact.

What do you t

monkey spanners
25-05-2014, 11:55 AM
Look at the expansion valve, it will tell you what refrigerant the system should be running (or the type of replacement you could use if its R12)

Maybe he means this stuff?


25-05-2014, 12:51 PM
I checked expansion valve and it is an R12 valve, the original by the looks of it...I checked it because apparently the engineer who fit the unit told him it's been swapped onto 'the modern gas' but left no note of what. So I thought perhaps he's retrofitted it onto R134a but can't have. I got him to find out what gas the engineer changed it for and he said R42d.

I told him yesterday that I've never heard of it, only R422d and to check it again and came back with same answer. I told him ive only heard of it, only R422d, and now he's said maybe it's that. I always thought that was for R22 system replacement not R12. I'm very tempted now to just walk away from it as I can't have the expense of a system failure due to poor information... how am I supposed to guarantee the work if I'm just guessing what's in it.

monkey spanners
25-05-2014, 03:34 PM
R422D is a R22 replacement, RS24 i put a link for is an R12 replacement. R422D will not work in your ssytem without component changes.

Your options are, other than walk away are,

Run it on a R12 replacement after removing the existing charge. Oil type, mineral or ester, or a mix won't matter. (just make sure its not overcharged, where did old oil go?)

Run it on R134a and change the oil a few times, it depends what refrigerants you normally carry, which would suit, the oil would be billable so no cost to you.

The second option may suit you better as there would be no need to get a bottle you may ever finish.

25-05-2014, 04:20 PM
I have told him to get the other engineer to fit it, he messaged me again saying that it is on R49 although he told me this morning that it was R42d both of which are supposedly told to him by this other engineer...I honestly don't think he knows what he's put in it ha ha.

It was the other engineer that recommended retrofitting it but I don't think he told him I would have to go back to change the oil out several times. He has already moaned about having to spend 450 to re condition the old one, which would've worked out much cheaper for him in long run because it could have been put on same oil and re piped and re commissioned and just run with whatever gas is actually in there.

By buying a new compressor and having it filled with synthetic oil hes made the job more awkward/expensive either way it is done, if I have to buy a bottle of R49 to keep costs down on his end it costs me money but if it is retrofit to R134a it costs him money for the extra parts and visits back to site...and I don't see why I should see myself out of pocket because he couldn't take my advice from day one.

Cheers for the help though Monkey Spanners, very much appreciated!!! :D

Divyesh Patel
13-06-2014, 02:24 AM
Hi Guys
In domestic unit of 134A we need to recharge the refrigerant within 2-3 years due to pressure drop ?