The compressor in my fridge died (i killed it by accident when troubleshooting a problem in the fridge). Its the typical PTC-start 1/3hp compressor, filled with R12. Original compressor is Matsushita (Panasonic) made in Japan

As i dont have the tools to pump/refill refrigerant i'll be hiring a technician for hte compressor replacement. Anyway, i called a few technicians out there and talked with them trying to figure out what work quality to expect from them and what quality compressor theyll be using

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i'd like a compressor that will last for another 20 years or more in the hot Israeli climate. Most techs here deal with Embraco and Danfoss, and a few shops stock Tecumseh. Some techs dont say the manufacturer name but when i ask for countery of origin they say EU or Brazil

Which of those compressors are good and which are to stay away from ?

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One tech said that he does not stock R12 and he is gonna fill it with R134a instead (into the existing evaporator unit, expansion valve and piping). Does not sound good to me, but is it fine ? Does it affect lifetime or reliability ? Efficiency ?

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What else should be controlled in order to get a good job (no contaminated refrigerant, no fragile bad weldings, anything else ?)

First a question: What did you do to kill the compressor?

Second: I'm quite surprised you want to replace the compressor in a fridge, here such job would cost nearly the same as brand new fridge...

For the fill gas: R12 vs R134a need different lubrication/cooling compressor oil (different chemical base), so if the compressors come pre-filled with some oil, you have to use a refrigerant compatible to that oil used in the compressor, so you basically have not much choice there.
But I would expect a quality service technician should know well the allowed combinations...

The starting PTC died, i noticed the compressor clicking on and off. To cool down the food in the fridge "for now", i took out the PTC, wired a switch instead and started the compressor using the switch (switch on the power to the fridge, quick momentary on to start and then off)

Thing is, the way i did it previously (on a friend's fridge) was to leave the switch on, plug in the fridge and flip the switch off. But here, i happened to plug in while the switch was off. When i flipped it on, the contacts in it welded from the spark and and the starting coil stayed energized for few seconds which i think blew it. Anyway when i measure across it now it shows open circuit

One thing i dont understand though, how does the fridge survive when the blown PTC is there, but did not survive few seconds with the coil powered through te switch ?



This fridg has simple mechanical controls. Everything sold in the shops now comes with fancy electronics (maybe except the cheapest, but also otherwise lowest grade products). I'd like to stay with the old fridge which was a premium grade fridge back in its time, and other than te compressor is in perfect condition (all gaskets, electrics etc)



The evaporator, expansion valve and pipes are not being replaced. I suppose there is some oil scattered in them too ? How would that oil accept the new refrigerant ? And aren't the pipe diameters and so on optimal for best performance/efficiency with R12 ?



And what else should i keep my eye on during the work ? The techs around here are not exactly high grade workers, many of them can go cheap and ugly when you are not looking. I'd not want for example a ms of pipes sticking out on the back of the unit, or leaking filling valves, or whatever else can go wrong due to bad worksmanship

The main winding is made of thick gauge wire, while the auxiliary is made from a thin wire, to get the necessary resistance for the required phase shift. But I would expect it will still last longer than few seconds and it's current will be so high, before this breaks, the overcurrent cut out opens, so protect the winding.

For the state of the present fridge:
And what is the state of the thermal insulation? The frequently used polystyrene foam tend to collapse over time and in fact that is the prime cause of excessive energy usage of the old fridges... I would expect this already progressed , so your fridge would have quite large part of it's life gone, even beside the compressor.

Other thing is indeed the interaction between the new and old oil, new refrigerant with the old oil, degradation of the old oil,... Pretty a lot of things asking for the system to go bad.

If something differ between different refrigerant in the fridge design (except the different oil), it is the compressor (pressure vs volume for given power) and an expansion valve.
The condenser and evaporator are sized according to the power, so don't need to be changed, piping is stock, so "one size fit all", so these should not have any trouble with virtually any phase change refrigerant.

Again, these things should be known by the technicians (they should at least know, what to replace when going to another refrigerant). And generally, if you do not trust them, then really better buy a new fridge. Don't forget the refrigerants are flammable, so their leak may cause a fire hazard. And the old Freon turns into a fosgen, when exposed to heat (when meeting the stove flame,...), so with any refrigerant it is quite important to have all the welding and leak check job done well...

The cutout operation apparently did not happen in time. When it was trying to start, the clicking periods of the overload were longer than the time it took to blow up

The thermal isolation is ok. I inspected it when cleaning out the ducts in th freezer and its still thick and solid and does not crumble or anything. If it goes bad, i'll replace it, polystyrene is cheap

I take it the oil is scattered o some extent in the pipes and coils, so if there is no way to clean it out of there, i think it may be a problem. I asked the tech that suggested the R134 why he wants to convert, the reason he said has nothing to do with the fridge, he just does not stock R12. Shall i prefer it to be filled with R12 ?

Currently the sytem is all welded. The sealed tube sticking from the compressor suggests that it was filled through this tube, then the tube was pinched, and its end welded off. In fridges that were refilled, the techs usually leave screw connectors for the filling. Shall i be concerned abut the screw connectors leaking over time ? Shall i ask for them to be removed and welded after filling is complete, or better to leave them on ? I dont want to fill it up every so long due to a leaking connector

Are refrigerant leaks possible to trace using soap like done with LPG systems, or are they too small to be seen and only show ther effects over few years ?

And finally : Out of Tecumseh, Danfoss, Embraco (thats what we got here), or out of Countries of Origin : Slovenia, France, Brazil, Italy, China : Do you have experience with any ? Which you'd choose ?

The question is, where you get the power to the switch: If it was not before the cut-out...


With the filler: I won't force them to any material they do not use every day. There are two reasons:
First if they have to work with something they are not used to, there is way higher chance they will screw things up, simply because the procedures may differ (fill pressure,...) and they may use the wrong one.
Second, it would be quite high chance he will install the compressor still filled with an oil, not compatible with the R12.

And for the expansion valve: As I have seen them, their manufacturing tolerance is quite high, so I won't be surprised the system is so insensitive for that, it could cover the different refrigerant as well...

Well I'm in the U.S.A. but we use the same refrigerants. As far as leaks are concerned, you can ask the technician to put dye in when they charge the system (it will probably be an extra cost, but not much). Here refrigerant dye is readily available and shows leaks by glowing a fluorescent color (often yellow) under UV light.
For R134a to be used in a R12 system, the old oil needs to flushed out of the system with a chemical flush, and a good technician will know how to do that.

indeed i just took the live wire entering the fridge... expecting to flip the switch off msnuslly in under a second i did not care much to connect to the harder to reach contacts of the overload, so the start coil was not protected

As i understand, a technician that would use R12 (with matching oil in the compressor) is preferred over one who suggests R134a without those convertion procedures

As for compresor manufacturers, which ones out of the 3 above / which countries of origin are you familiar with ? Is any better than the others ? Are there known issues with any ?

Update :

After much trouble acquiring a compressor for R12 (apparently those things are now banned, but i managed to find a couple year old NOS one, with factory seals and all), fridge is up and running

But now i noticed. The new compressor is running hot (i just can still hold hand on it continuously) and the liquid line on the exit of the compressor is hot to the extent that i cant touch it for long. I dont remember so high temps in the old one. And the suction line is intermittently covering with fine ice up to the compressor

Suction pressure is ~5 psi

Is this ok or sign of over/undercharging with refrigerant ?

This should be normal: After compression the gas is hot, that is normal.
Probably the new compressor have higher power than the old one, or the old one could have leaky valves after the years (it deteriorated slowly and you remember it only from the recent, already deteriorated state).

As I remember chillers I had to deal with, the output from the compressor was always hot, so you can touch it only very briefly...

Isnt the new compressor supposed to run more efficiently (so heat less) than the old one ?

Im fine with the scorching liquid line, but im unsure if its right for the compressor itself to run that hot, after all the insides of the compressor "enclosure" are not liquid refrigerant

Its also not very silent, it more noisy then the old one. Is this ok (varying from type to type) or another possible sign of wrong amount of refrigerant ?

For the amount of refrigerant I can not say.
But I guess than once running, the excess amount of refrigerant will simply stay condense and accumulate at the end of the condenser, so it will settle to pressures corresponding to temperatures within the system (we are talking about saturated vapor there, so the pressure is controlled by the temperatures). And so therefore the system should be quite immune against amount of refrigerant variation, once there it is sufficient.
But I'm not sure with that - I'm no expert in refrigerator designs, I only deduced from the basic principles, but I could overlook some important effects...

And quite some heat inside of the compressor come from the gas itself: The first part exposed to the compressed gas heat is the compressor head and this is cooled by the oil. So quite some of the compressor heat come from cooling the gas and that mean it is not an inefficiency.
As I observed most of the compressors to really run warm (so barely to hold the hand on them), I would assume it is normal.

And how about amount of oil ? Ifthe compressor came factory sealed this means that all the oil required is there or it needs extra (it came with oil, question is for quantity)

Ill upload now a couple pics/vids too

Beside the lubrication, the oil is there to act as a compressor piston sealing and motor coolant. And the last function is the most sensitive for the insufficient oil level: The motor will overheat and burn, without the case even warming up.
Normally the circulating oil make the thermal bridge to the compressor case surface...

Guy came and discharged quite a bit of refrigerant out - ~10-15 sec of pressing the service valve open while power is off, i'd say there were several grams thrown out. Temps appear to be the same now but the suction line does not freeze, it stabilizes at about room temp right near the compressor and compressor works somewhat more silent now. We'll see what happens next....

I asked about the oil, he says the compressor comes with the right quantity