Why can't I use Pag in a chiller system running R-134a?

[The MG Pony]

Ok here's the situation. I am building a small chiller plant for the sake of building it and learning, It is an old Copeland RSN2-0050-IAA Compressor that I have added a receiver and TXV & such. Now I know for R-134a you are supposed to use POE but I see they use PAG heavily in the automotive industry with R-134a as well, so why won't it work in a hermetic environment?

PAG being so much cheaper will make this project more affordable so it would be nice if it will work, but if it will not I won't do it as I plan to do this project as if it where a mission critical plant, as the whole Idea is to learn to properly build a fully functioning system properly and to have it run reliably.

[Brian_UK]

Have you tried Copeland themselves to get their advice? It might save you a blown compressor.

[The MG Pony]

Hmm good point there. but I would still enjoy hearing all of your guys seasoned opinions

[chillin out]

I don't know the answer but...

If you think about how the comp gets it's oil to lubricate itself you might come up with the answer.

You are talking about 2 completely differant comps here.

I think the PAG oil is too thin, meaning it might not get "kicked" up by a recip comp, or it may vaporize and you will send the whole oil charge round the system.

Just a thought.

Chillin

[DeB]

I don't honestly know the answer to PAG oil but PAO oils I have found work well in some applications. I know some milk vat mechanics that use it in vats that have been converted from R12 to other non CFC refrigerants as they had oil return problems on converted milk vats and PAO oils being less miscible tend to stay in the compressor. The added bonus is it is doesn't have a high affinity with moisture as does POE. In the early days of POEs we were told to keep the mineral oil percentage below 1 or 2% of total oil charge when changing refrigerants to HFC with POE oil.I tried various mineral/poe oil ratios on smaller (under 5HP) 134A hermetic systems and found no long term problems with up to a 25% ratio.although the test was only on a small portion of units.I should also say I did not do any scientific testing. My only proof being the units still operating 2 years later. Why not try? Maybe you will teach us all something!

[afeef]

i dont understand these symboles:

PAG oil

PAO oil

would you please explane it to me
thanks

[chillin out]

polyalphaolefin (PAO) synthetic base fluids.

polyalkylene glycol (PAG).

They are just 2 names of oil used.

Chillin

[chillyhamster]

Think about it !. Automotive a/c ie. cars, the comp is belt driven. Your Copeland has a dirty great heat providing electric motor in it. Also the electrical conductivity of the oil may not be suitable.

[The MG Pony]

Ah K, then if it is electrically conductive no, it will not work, but I did not know this and hence why I asked, I am still just starting to learn this field, and so I move slowly to learn the basics well and you can't get more basic then oils eh

I just knew that PAG and POE where compatible to R-134a, but I did not know the fundamental reasons why one wasn't used instead of the other or vice versa.

I thank you all greatly for your input and hope to keep this thread going (I now know it won't work due to the conductivity) but for the educational part lets keep on if all are willing

[wambat]

PAG oil is extremely hygroscopic and has a low dialectric strength so it is unsuitable for semi-hermetic and hermetic compressors. They are therefor mainly used on car AC compressors where specific demands are placed on lubrication and optimum solubility is required because of the high oil circulation rates