HC blend and oil return. still wondering

[wulff]

Girina recently asked a question regarding how much oil migrates through a system and returns to the compressor.
I have a similar question, I am using an HC blend to replace 134a in a large ice bank cooler. There are a lot of tubing as the 'evaporator' is a series of tubing in a 100 gallon water tank. It has an accumulator on the high side and the low side. When I tore the system apart (due to failed compressor) I only was able to drain about 5 ounces of POE oil from the compressor.
So I think failure was apparent (oil starvation). When I installed the replacement compressor I added more (about a quart and a a half more ) than the one quart oil I drained (alkybenezene oil) from the compressor I am using.
Why didn't I find ANY old oil in the accumulators? Does POE oil not move through the system?
I am worried the HC blend (Enviro-Safe Industrial 12a) will move the oil to the accumulators and just stay there, starving the compressor.
Would you experts recommend adding even more oil to the system?
The original charge was 13 pounds of 134a, I can't get help from the manufacturer because I think they are idiots, I called 3 times and was told to use 8, 13, 14 pounds (they change the amount every-time I call!! the plate says 13 pounds so I will go with that but use less due to HC).
HELP!! My boss is wanting to get this running but I don't want to give it any reason to fail right away!

[monkey spanners]

All the oil from the compressor will eventually leave the discharge connection as a normal function of proper compressor lubrication, if it is not returning to the suction or sump connection at the same rate the compressor will eventually seize up.
I am not sure if poe oil is suitable for hc refrigerants, i have a feeling it isn't and mineral oil or poly-alpha olefin is more suitable.

Has this system ever worked or is it a new build? If it has worked before then it is probably not a piping design fault that is trapping the oil.
If the system has multiple txv's or cap tubes then check these are all working at capacity, a blocked or partially closed expansion device can cause the oil to be trapped in that section of the evap due to low refrigerant velocity.
Putting more oil in than than the compressor holds is likely to lead to a liquid slug returning to the compressor once there is enough collected to form one.

I would try blowing out the evap (and other parts of the system if needs be) with nitrogen to remove the oil therein before running up the system, with the compressor charged with the correct amount and type of oil.

Jon

[NoNickName]

I am not sure if poe oil is suitable for hc refrigerants, i have a feeling it isn't and mineral oil or poly-alpha olefin is more suitable.


It isn't infact. PAG is the newest oil available on the market, and gives the best results with HC refrigerants and R744.

[wulff]

Thanks guys, I am using Alkybenzene oil 200 wt I think I may have used too much oil as it is vibrating badly and it comes and goes, I listened at the expansion valve and it sounded like it was surging, like it was building pressure then going through the expansion valve (the valve is a balanced design made for r134a or R12, the capillary tube is for r134a).
I took some of the oil out and it seemed to help, could the condenser be slugging? I blew out the condenser and got some more oil out of it but don’t know if it’s enough.
The expansion valve is adjustable but the counter guy at the refrigeration place I buy stuff said NEVER adjust it but I am wondering if I should?
Should I install some kind of cheap oil separator on the high pressure side?
What about using an orifice instead of the expansion valve?
One more question, on the solenoid leading to the expansion valve there is an adjustment, why would this be adjustable? Don’t you just want it to (when activated) to cause suction to shut off the compressor?
When I remove all the lines and let the compressor run it is really smooth but as soon as it starts pushing the ref. thru the lines all the problems start.
All the tubes coming off the expansion valve turns frosty when it’s running but the noise and vibration tells me I am doing something wrong.
Please steer me in the right direction oh, gurus of the refrigeration world! LOL!