R12 recovery how-to with refrigerator compressor?

[james89dx]

I started over a year ago about issues with my 89 Dodge pickup. Rather than revive that thread with this slightly off-topic question I thought I'd start a new thread just for this.

Recap on this truck - totally 100% new R12 system but high side pressure is way too high and getting 60 degree vent temps. Signs point to restriction and/or inadequate condenser performance. I already changed the condenser once along with the expansion valve which resulted in no change in performance. I also added electric fans to the condenser and still no fix. I've been working 60+ hour weeks for the past year and as a result of that and new projects I haven't been able to work on this truck's AC any further. I haven't driven the truck much in the summer and when I did I just live with the crummy vent temps.

I have since stumbled upon a potential manufacturing defect in the high-side rubber line between compressor and condenser. It appears to be a sort of plastic staple or some such and maybe just maybe this might be my elusive restriction. I want to remove/inspect and maybe replace this line. However, I have already wasted so much R12 working on this truck (2.75 lbs a pop) I don't want to waste even more refrigerant so I would like to rig up a way to recover what's in there - especially as I may be going through a few more tests/part swaps on the truck.

Cornbider mentioned this in my thread:

"I picked up a surplus refrigeration compressor for a 'fridge, changed the oil to match the systems I work on, and use it to pump out a system. I think I paid $25 for the compressor and had to braise on some fittings. Depending on how big a vessel you are pumping into, you may need to cool the vessel so the gas condenses.
For this type of operation the smaller the displacement of the compressor the better. You want to give the gas a chance to loose its heat and condense."

I would like to try this and can buy a refrigerator compressor but would not know how to go about it beyond that. Could somebody explain this procedure a little deeper for me? How do I change the oil in the compressor and what sort of fittings do I need to braise on? I have an empty 30 lb jug of R12 I can use for the recovery vessel but not sure if that will work and/or what modifications I need to make to it. Is there anything else I need?

[Tom Greenleaf]

James: Early for me your post didn't show properly or well so bear with me. I removed the "hyperlink" where you said ""this thread" was not in format for Google to allow it? Don't ask they now own this joint.

I take it you want to save R-12 right? Recovery items are gone anywhere near me so making your own as Cornbinder has said how here or somewhere or others using dry ice and an empty and vacuumed out clean tank. AYOR on that it works and is clean enough to use.

It's been a while but tanks to be discarded have been reported just with a hole drilled in them so they are no longer useful? I don't think we (people) are paying for the recovery machines anymore NONE known here.

So, try if you want if you need more it's said there is still plenty. By now expect to lose some in finding or making hoses for use again plus the connections. R-12 was tolerant of everything could use hose clamps now look for "fuel injection" clamps I can find full circle grab or spring for a crimper.

For home type refrigerators IDK. I think you can tap in like for an ice maker - I've never done that so can't prove it. For those it really is better to replace with another refrigerant you may find 152a works sold as duster for blowing dust mostly is cheap marked 152a. IDK again and AYOR but many reports it works fine, compatible with mineral oils. You do need a good side tap for cans of that.

I can see this for a real classic refrigerator like a "Coke" or soda machine but not for daily use for home/biz use unless you don't mind it's seriously an energy pig otherwise worked great!

Good luck. Pls. skip the hyperlinks are a method to spam sites not listed here NOT to do that just copy paste the post/thread if from here it would be fine it shouldn't if from another site, or sent a reader off to advertising wouldn't be allowed.

Cornbinder may be by to fix all this mess it's giving me fits just to post on this it was blocked to public view and IDK exactly why??

[Cusser]

I HAVE recovered refrigerant successfully a few times in the past few years, mostly R-12.

I have a metal canister/gas cylinder, about 12 inches by 4 inches diameter, with a shut-off and flare valve. I attached it to my gauge set (middle fitting), attached high side hose to the vacuum pump, and low side hose to low side fitting, and had the canister sit in a dry-ice-alcohol bath in a bucket. I pulled a vacuum from the canister (only) then closed it off and opened the canister to the low side, and my refrigerant all went into my canister for future use. The refrigerant comes over, condenses to liquid, so the canister continues to be at vacuum, so refrigerant continues to come over. Then I re-added it after the repair.

The cannister can have either a flare or an Acme R134a fitting, doesn't matter as long as it fits your gauge set.

[james89dx]

I HAVE recovered refrigerant successfully a few times in the past few years, mostly R-12.

I have a metal canister/gas cylinder, about 12 inches by 4 inches diameter, with a shut-off and flare valve. I attached it to my gauge set (middle fitting), attached high side hose to the vacuum pump, and low side hose to low side fitting, and had the canister sit in a dry-ice-alcohol bath in a bucket. I pulled a vacuum from the canister (only) then closed it off and opened the canister to the low side, and my refrigerant all went into my canister for future use. The refrigerant comes over, condenses to liquid, so the canister continues to be at vacuum, so refrigerant continues to come over. Then I re-added it after the repair.

The cannister can have either a flare or an Acme R134a fitting, doesn't matter as long as it fits your gauge set.

This is the exact sort of thing I was looking for.

I guess my main question is the canister/gas cylinder you mention - could you point me towards something I could use for this task? Did you have to add on our own shut-off and flare valve?

Can I re-purpose my empty R12 canister for this? It's a 30 lb jug and I'm the one that emptied it so it doesn't have any holes or anything poked into it but I assume I would need to somehow add the proper valve as I'm sure the current fitting on it is one-way.

*edit* To add to this - my R12 30lb jug has the black valve handle and it appears from some Googling that the old black handle valves are NOT one way valves? i.e., I should theoretically be able to use the 30 lb jug without modification?

[Cornbinder89]

For quite some time 30lb kegs have a one way check valve that prevents ANY gas or liquid from entering the keg. SO first order of business is to determine if the keg you have can be filled, it is highly likely it can not.
As far as using refrigeration compressors, any for R 12 or R22 will have mineral oil so that will be compatible with R 12, if the compressor is for 134a you'll need to drain before doing anything else and re fill with the same amount of mineral oil.
Most refrigeration compressors have 3 tubes, two medium and one small. The small tube is the outlet, and one of the medium tube should be marked "IN" the other tube is the process tube, which is used to service the system when the inlet and outlet are braised into the refrigeration equipment, so just another low side tap. The reason one is market in, and you should not use the process tube for the low side, is how the returning refrigerant is directed inside the compressor, it is generally directed over the hot compressor to cool it and vaporize any liquid that might find its way back to the compressor, while the process tube just go into the "can" (low side).
So once you have a compressor, you need to braise some 1/4" flare fittings (use refrigeration flares with schrader valve to keep air and other contaminants out when not in use).
If you are pumping only a few lbs into a large (30 lb keg) then cooling is not an issue, if you are using a much smaller container, then you need to run the outlet of the compressor thru a cooling bath to condense the gas into a liquid.
You hook the refrigeration compressor low to any connection on the vehicle (vehicle not running) and pump the refrigerant into the container. I connect thru gauges so I can see when the system is empty (vacuum on both high and low gauges).
You will always loose some refrigerant, some will stay in the keg, some in the compressor, but you will save most of it.
To go the other way you can reverse the connections on the refrigeration compressor or draw it in using the vehicle compressor.
Again, unless the keg in question is around 40-50 years old, it is likely to have a check valve in it, and the only way you can use it is to remove the outlet spud and valve and weld a new one without a check valve in its place.

[Tom Greenleaf]

Off the wall! Ah (I didn't say this but guess I am?)

Note that junked propane gas grills are a source for brass fittings if creative with torches and a threaded hole! So are tire valve cores at the risk of your fingers wire wheel off al the rubber expose a barbed real Shrader valve stem also sold now at many hardware stores just stack up the assorted adaptors that get to where you want!

Real junky gauge sets you can also get an Acme male OUT and use they don't sell Acme new TMK.

IF really determined to find new R-12 it's still out there find old (now really old) most for marine air horns that were and are required are/were R-12 some still kicking around don't look around me I have them all. Real can use the long name of R-12 it really is!

Been ages they may still sell or "deposits" only for any gas uses the 1/4 flare, red and blue knobs while upright work both ways to dispense gas or liquid without turning tanks.

I know it's local to me the places anywhere don't touch R-12, hazmat or not just drill holes and recycle the metal there's simply no call to warrant capturing it anymore.

Can buy it new if you check around or recovered ask as it's out there even made new apparently not hard to make for non NATO complying countries so it will probably never end?

[Cornbinder89]

Just about all commercial refrigeration use 1/4" flare, even kegs 134a for commercial refrigeration have 1/4" flare, only kegs for automotive use are acme thread.
Too many mixtures and refrigerants used in commercial systems to have different threads for each type. Finding a 1/4" flare gauge set should be no problem.

[Cornbinder89]

*edit* To add to this - my R12 30lb jug has the black valve handle and it appears from some Googling that the old black handle valves are NOT one way valves? i.e., I should theoretically be able to use the 30 lb jug without modification?

I have more than one jug with black handle and one way check valve, so I would say the internet info is wrong. I think most if not all kegs younger than 30 year old have the check valve, may be refrigeration kegs don't but those sold for automotive work do.

[Tom Greenleaf]

Crack me up - "The Internet WRONG?" Don't even start with that one!

[Cusser]

This is the exact sort of thing I was looking for.

I guess my main question is the canister/gas cylinder you mention - could you point me towards something I could use for this task? Did you have to add on our own shut-off and flare valve?

James - we had empty canisters from gas standards at work, would be thrown away so I have a few. They already had a shut off valve, and I threaded in a flare fitting. I don't have time this morning to take/upload a photo of what I have, but photo attached is same canister. I have not given any thought as to how much I'd let one go for.

[james89dx]

So after work last night I decided to check my empty R12 canister. It's an actual DuPont "Freon" branded jug with a black valve handle and no idea as to its age. Anyway, it is definitely NOT a one way valve as I can use my air compressor and rubber tipped nozzle and shoot air into the canister.

Having said that, I also did some testing on the line I thought maybe had a restriction in my discharge line and I now believe it most likely does not. Like I said, it seems to have some sort of plastic staple deal in the rubber but this must just be superficial and not causing any blockage. I used my infrared thermometer to test the line in front of and behind this spot with no change in temp. If it were causing any restriction, shouldn't I notice a drop in temp behind the restriction?

I'm really running out of ideas on this truck. I have never been any good or knowledgeable at "reading" sight glasses but I shot a video of mine last night on the drier. Can anybody discern anything here that would be telling one way or the other?

https://youtu.be/Goj25X2nS3U

[james89dx]

Thanks Cusser and Cornbinder for the info. What would be the advantage of trying to rig up the refrigerator compressor setup? Would it be more effective overall than using the dry ice method or would it simply be faster?

[Cornbinder89]

If you have access to dry ice and alcohol and a small container, for a "one off" use that would be cheaper, speed wouldn't vary much with either method. If you think you might be doing it more often, it is nice having the compressor.
With both methods you will loose a little, some stays in the compressor and some in a bottle but you would save the lions share.
You would need both dry ice and alcohol to cool the bottle, dry ice alone will not make good enough contact to keep the bottle cold, you need some liquid to transfer the heat to the dry ice, and it needs to cool well below zero for it to be effective.
When I made mine, Grainger was selling "surplus" compressors for cheap, all I added was the braise on flares with the shrader valve.
I used an old BBQ propane tank that i evacuated, but I don't re-use the gas as I am not sure that there is no propane in the mix. Since all my work is 134a and that gas is cheap and easy to come by, virgin gas make sense.
An old CO2 fire extinguisher bottle would work well, and would be less of a concern if you wanted to re-use the gas.

[Cornbinder89]

Sight glass just shows the state of the refrigerant at that point. It could be undercharged and show bubbles like that or it could be too hot and fully or over charged and show bubbles. What it shows is at that temp and pressure the refrigerant is boiling in the liquid line. WHY it is boiling is the question. From your other post, the high side is very high, and you side the line from the condenser is hot, so you really can't assess state of charge by bubbles alone.
If the pressure gets high enough you will always have liquid, but it is also true if the temp gets high enough you'll always have vapor. Fortunately there is a relief valve to prevent pressures getting so high it ruptures
liquid or vapor is determined by both temp and pressure together, so any change to one or more will effect the remaining.
In a proper functioning system, all the refrigerant will be liquid when it exits the condenser, but it will also be cool, a few degrees above the air temp passing thru the condenser, if both these thing are not true, then you HAVE to sort out why before proceeding.
If the outlet of the condenser is cool, but the refrigerant is boiling at the sight glass, that would suggest a low charge, but if the outlet is hot, it could be many things, it could be overcharged or it could be the effective area of the condenser is too small for the heat load, which includes a condenser that can't transfer the heat to the cooling medium for what ever reason..
In an overcharged system, the pressure in the condenser is high enough that some refrigerant turns to liquid, as liquid starts to fill the tubes of the condenser, it reduces the area available for hot gas to be cooled to liquid. When gas is cooled to the condensing point, the volume it takes drops by a huge amount, like 100x., so if the condenser can't rid the heat, the pressure rises until it can condense at the higher temp, the heat gets recycled back to the compressor where more heat is added and the cycle continues until something blows or shuts the system down.
While a sight glass can be helpful, it is not a absolute indicator. On a cool day with a properly functioning system that is under charged, you will still see all liquid in the sight glass because there is very little heat load on the system an most of the refrigerant is in liquid form. Conversely, on a very hot day, and a properly charged system you might see little bubbles as the heat load exceeds the capacity of the system to move it. Taken together with pressure and temp readings it will give a fair indication of the system if it is working as it should.
The Refrigeration cycle is a "floating" system, make a change to any one thing, and it effects the whole rest of the system. Because phase changes are involved, it can be hard to "see" all the effects directly. A rise in pressure lead to condensing of gas to liquid, a rise in temp leads to liquid boiling to gas, the both happen until they reach an equilibrium. Any change will effect the equilibrium point.