Oil Refrigerant Compatibility 1

[Webber]

We have a customer that is currently setting up a 10ton R22 cooling system using mineral oil. In future, they will be switching to R407c systems which use POE oil. Is it possible to run the R22 system with POE oil? What are the anticipated concerns? We would have an oil separator at the compressor outlet to return the oil to the compressor which should eliminate too much concern with oil carry over and logging in the system.

Also, we generally calculate oil carryover on a R134a with POE oil as 3-6% by weight. Is this number the same for R22 with mineral oil? As the mineral oil is not miscible with the refrigerant, I would expect the oil return to be more difficult to handle and rely more heavily on line sizig.

This brings me to a third point. Our customer reports the oil in the suction accumulator sits on top of the liquid refrigerant and is not returning to the compressor. Is anyone familiar with this phenomenon? If so, any solutions?

 

[ClydeMule]

Webber,

1. You can run R22 with POE, but you can't run 407C, 143a, etc. With mineral oil.

2. I thought mineral oil was miscible with R22, but not with the HFC's hence the use of POE. Dunno about the carryover %, our stuff is so close coupled we don't worry about it too much.

I guess that is something to look up tonight.

3. Liquid in the suction accumulator.

There isn't supposed to be any. The way you describe it, their accumulator is partly full of liquid, with the oil on top like salad dressing. Liquid doesn't sit in the accumulator like that. Gulps of liquid might flood into the accumulator from time to time, but it doesn't stay there. You are describing something like a surge drum in an ammonia system.

Also, how can they "see" what is going on?

What it sounds like is the accumulator is installed backwards. The inlet tube terminates a couple of inches below the top. The outlet tube is like a "J," it draws from the top, goes down to the bottom and then bends back up and goes out the top. At the very bottom if the bend is an orifice to meter oil back into the line. Since the velocity drops, the oil droplets fall to the bottom.

If installed backwards, the suction line can't pick up the oil.

If this is a relatively new installation, I would think this is the problem. The other is that there is crud on the oil orifice.

By the way we still use R22 but get more customers who ask for 407C. We have to then special order the compressor with the right POE charge. We are thinking about getting all POE compressors so that when we use an HFC we only have to charge a different gas. Different TEV of course.


Hope this helps.



Clyde