Converting old Bev-Air Keg fridge from r12 compressor to r134 compressor

[barkerw]

I bought an old Bev-Air (DD50) Commercial Keg fridge about 10 plus years ago. Its r12 and the compressor has died on me once so far. We replaced it with a used r12 compressor and it worked for another 5 years. Well, it has kicked the bucket again. This time i enlisted the help of my cousin who works Whirlpool Refridge Dept. He suggested we replace the bad compressor with an r134 unit. We found and purchased an embraco unit that was compatable. We vaccumed the lines and ran nitrogen through them and tested for leaks. All was good and we gave it a charge of 9 oz of r134 (it took 9 oz of r12...not sure if there is a conversion chart or anything).

It cooled down very slowly and eventually got down to 40. Stayed there for a few hours until i buttoned up the compressor chamber with the vent covers etc. Then it stopped working. He came back over and we vaccumed and nitrogen and recharged again. This time it worked for 2 days and then quit. I have the Tstat set to 4 (1-10...10 being coldest). At 4 it drops to 40 degrees which makes me wonder if there is some type of conversion problem or something with the amount of coolant. Basically it doesn't work again. I unbuttoned the compressor chamber again and turned it off for an hour and now it seems to be cooling again. For how long...who knows. Anyone have any ideas on what might be happening? The copper line off the compressor is cold and damp. The T-stat clicks on and off and does trigger the compressor. I don't know what is going on.

Update: It is not cooling again

[akaothermick]

Plugging in a compressor for R134 without changing the expansion valve or expansion port, capillary or whatever it uses for expansion is just a problem, its sounds like a mix and match, the systems are different, this is an example of a similar issue in the automotive conversions, its close but just not quite there, R12 apart from its environmental issue was a efficient refrigerant that worked well,

[Dan O.]

Clarification needed

Stayed there for a few hours until i buttoned up the compressor chamber with the vent covers etc. Then it stopped working.

What exactly do you mean by "stopped working". The compressor stopped running??

Basically it doesn't work again.

Again, clarification is needed.

Was the compressor running? If not, was it being powered? Was it overheated?


If it WAS running, what was its wattage draw? What was the high side pressure? What was the low side pressure?

we gave it a charge of 9 oz of r134 (it took 9 oz of r12).

Generally, less R134a refrigerant would be required. For 9 oz. R12, 6.8 oz. R134a would be recommended.

A problem with just the refrigerant charge would not usually affect operation of the compressor, only the temperatures and pressures. If the compressor stops operating, you likely have problems other than just the refrigerant charge.

JMO

Dan O.
Appliance411.com
The Appliance Information Site
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[barkerw]

Is it possible to replace the expansion port and capilary (it does have a smaller capillary tube it uses)? If so, are these things i could cut from an existing r134 fridge and braze them on?

I apologize for the lack of information, all i really have to go on is what my cousin and i tried so far, he has all the tools so cannot check the pressures and wattage draw. When i said, "stopped working", i meant it stopped cooling. I know that the compressor was getting very hot but i thought that was normal. The tubing was getting cold coming off the compressor. If the compressor is shutting off, would the copper line stay cold?

Are there some things relatively easy for a novice to check that would give you more info to go on?

[akaothermick]

Sounds like the system is close to working but you might have to experiment with the quantity of refrigerant, before cutting out the expansion capillary, R134 will not in a R12 system be as efficient but it should be acceptable for your type of use. The compressor getting hot is good, the line out to the condenser should be hot, the line from the evaporator into the compressor should be cold, just where the refrigerant boils off after the expansion port/line as it goes into the evaporator coil is dependent on the amount of charge, put some in or take some out, till you get it where you find it cools best, brazing a 134 cap line is not really going to help much, as condenser and evaporator sizing also is part of a well designed system. Just experiment with the charge. It never will be a "drop in" refrigerant change so don't expect a flawless conversion.

[HayZee518]

has anyone checked the "boiling point" of the two refrigerants? nobody mentioned that! also compatibility of the internal O rings. buna-n doesn't like 134a. Refrigeration oil is different for `134a. Check with "sporlan" for expansion manifolds.
134a operates at a higher pressure on the high end than r-12.

[Dan O.]

The compressor should NOT be "very hot"

I know that the compressor was getting very hot but i thought that was normal.

No it isn't suppose to get "very hot".

While operating properly, you should normally be able to place your hand on a domestic refrigerator's compressor. (I'm assuming that's what was installed - no details were provided). If a domestic refrigerator compressor is getting hotter than that, there is a problem.

BTW. Do not allow the compressor to run hot or damage to the compressor windings can easily result on an R134a compressor! They are MUCH more susceptible to overheating than R12 compressor models were. If it's overheating, disconnect it from power until it can be serviced!



Were the correct relay/overload installed onto the replacement compressor? Using an older RSIR type relay (like would have been in the appliance already) on a newer RSCR design compressor would usually result in overheating of the compressor. Most new compressors come with the proper relay/overload for it. Hopefully it was used.

The tubing was getting cold coming off the compressor. If the compressor is shutting off, would the copper line stay cold?

No, the refrigerant line wouldn't stay cold and shouldn't get noticeably cold regardless. The suction line getting cold is usually a sign of a refrigerant overcharge, or a split heat exchanger, on a domestic refrigeration system.

has anyone checked the "boiling point" of the two refrigerants?

Their boiling points are different which is the reason for needing to adjust the refrigerant charge. The difference however is only relevant if we know the back pressure of the refrigerant system, which was not supplied.

You can either recharge the system using a specific amount of the replacement refrigerant or by back pressure. Whirlpool provides a R12/R134a charge table as part of their R134a training material. It should be available to the Whirlpool tech. I quoted the equivalent amount of R134a suggested to replace 9 oz. R12.

The ideal back pressure for the refrigerant used would depend on the temperature you want to achieve in the evaporator coil.


JFYI

Dan O.
Appliance411.com
The Appliance Information Site
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[barkerw]

I just noticed something very wrong. Both the condenser fan and the evaporator fan are sucking air and not blowing out. Correct me if i'm wrong but that isn't right is it? I cut the lead from the compressor to the fan and switched the leads but it still runs in the same direction. Likewise i switched the fan leads in the evaporator fan and it still sucks air in and doesn't blow it out. Anyone know what is going on.....is this right?

[Dan O.]

Both the condenser fan and the evaporator fan are sucking air and not blowing out. Correct me if i'm wrong but that isn't right is it?

It could very well be as it was designed, I don't know the specifics of the model in question. The important thing with the condenser fan is air flow across the condenser coil. Is that occurring?

I cut the lead to the fan and switched the leads but it still runs in the same direction.

You can not switch the direction of an A/C motor just be reversing the wiring. If either of the motors were still the original ones, my guess is it was probably performing as it was designed to.


I wouldn't suggest you make any other modifications until you get the refrigerant charge corrected. That for certain is a problem.

JMO

Dan O.
Appliance411.com
The Appliance Information Site
=D~~~~~~

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[barkerw]

The condensor fan pulls air from outside across the condenser and on to the compressor behind it. I'm guessing that is the way it is supposed to be. The evap fan was sucking air into the evap compartmemt. I confirmed with bev air tech that this it should be blowing air out of compartment. I took fan apart and reversed the motor.. it's blowing out now....Fingers crossed. Whirlpool engineer and bev air tech both said the original cap tube should be fine with r134.

[HayZee518]

I hope you guys know what the different components are supposed to do. The condenser is supposed to remove latent heat from the system so the refrigerant can cool down a circuit. You guys do know that the refrigerant charge changes from a gas to a liquid don't you? Also, wattage is a mathematical calculation between voltage and amperage. you can't read it directly. wattage = power. P=EI. In the evaporator where you have a high pressure cappillary line exiting into a larger diameter tubing you have a pressure drop. This is what causes refrigeration. Cold liquid freon absorbs heat and changes back into a gas. Liquid cannot be compressed. A gas can be compressed. The condenser gives up latent heat to atmosphere.

[barkerw]

Ran all night and same result. Stopped cooling. The compressor is hot. Hotter than you would want to just lay your Hand on.

[HayZee518]

what are your pressures - low side and high side? has anyone injected refrigeration oil? what type and viscosity? rarely is 134a used alone, its usually in what is called an azeotropic mixture like R-402.

[Dan O.]

Did you ever figure out the problem?