Regular Guest
Always on a Friday of course. this is an R22 low temp rack. Oil issue upon oil issue upon oil issue, after we fixed the last oil issue. Clogged TEV screens every 6 months. Stuck oil floats and so on and so on. I guess it generates a lot of business for the company...but what does one do to fix this on a long term scale? Convert the whole system to something else, right? Is there something we can convert it to relatively easy or no? New compressors, new TEV's in everything? What else?
Professional Member
Isn't the cause of this type of thing the high compression ratio inherent to R-22 low temp systems? I'm still learning this trade, but I'm betting the higher ups at that store likely have remodel plans, and that in the future you'll be replacing it with something more LT friendly...but in the meantime "just keep it running" is probably what they're saying/thinking.Originally Posted by cswenson701
Professional Member*
Have changed a few racks over to 507. Oil issues with R-22 on low temp racks I must say have seen a few like you explain.
Converting is something that you could look into.
Also is the installation fairly new? Or any changes to the system recently? When the new piping was done, did they purge with nitrogen ?
Professional Member
Keep the R2 and convert to AB oil. Sounds like the rack still has mineral oil in it.
Regular Guest
agree with ab or poe conversion and triple check demand cooling on every compressor.
Regular Guest
Ripp the whole thing out and put in a secondary loop CO2 system in like all the cool super markets do. XD
No but I'm having the same problem out at a red apple right now with oil level failures on a split head med/low temp 22 rack. Can't get the damn compressors to equal out. I'll have 2 compressor always good and the center two always getting stuck floats or bad valves that end up in flooding and starving the far two, or the first two just run too damn much and one of their pumps go out. The oil separator has been changed A few times and the system has had countless r11 flushes and a poe convert..
Mind you, this rack is like older than I am. And has a grossly poor design. Oil problems can be a real on going nightmare on old equipment..
Professional Member
I would start with this...
What's your suction pressure?
What's your discharge pressure?
What's your rack suction superheat?
What's each compressors discharge line temperature?
If it's gas defrost, what's the differential?
Something must be wrong. And it isn't just because its LT 22.
Professional Member
slam wore out compressors with a fair amount of blowby will cause oil problems that seem to be unsoveable
Professional Member
R-22 low temp requires a little TLC, but it isn't as bad as you are describing unless it is horribly maintained.
Professional Member
the good news is, you can solve root cause of whats cooking the oil.
Professional Member*
It's not the high compression ratio...it's the thermodynamic properties of R-22 the result in high discharge temperatures in LT applications.
As a few have said, if the system is set up properly you can operate trouble free. The decomposed oil is a sign of high discharge temperatures. Your job is to find out why.
Membership Chair/ARP Committee / Professional Member*
Why don't you try running a synthetic oil? What are the clogs? Sooty looking yak? Have you ever had a head off? Are the valve plates all black with sooty looking yak?
Low temp R-22 runs huge DSH and DT numbers. Mineral oil doesn't like it and will coke. Liquid injection will work to some extent but going to a synthetic oil which will take the high temps in the heads would be a better idea I think. POE will run you silly with cleanup and filter changes for a while so maybe that Calgon oil (it pisses me off that I can't remember the name right now) would be for the best. I used to use it all the time on compound compression low temp compressors.
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
Professional Member
high compression ratios are so related to high discharge temperatures no matter what gas or temp. Page 3.
http://www.hvacrinfo.com/cope_ae_bulletins/TAE1268.PDF
Professional Member
Here is a better way to think about this. r22 just happens to have such a composition that it can have excessive discharge temps under normal compression ratios. But anything with excessive compression ratios will certainly have high discharge temps.
Not sure of your response, just wanted to clarify.
New Guest
I've run into a lot of the same problems on lt 22 rack systems. Sometimes you'd think it would be easier to just post a guy there permanently to save the headaches! Not sure if anyone else has used this but i e had really good luck with AC-Renew from nu-calgon. Made for 22 systems it blends with the oil and seems to keep it from breaking down as fast. After a rebuild on one of the semi-hermetics the gunk built up on the plates was way less after using this stuff and have yet to run into the same oil related problems on the others (knocks on wood). Just an option I figured I'd throw out there, that and a lot of Tylenol :-)
Professional Member*
Completely agree...higher compression ratios do result in higher discharge temperatures.
Because of its thermodynamic properties, R-22 has challenges as a low temp refrigerant...that being high discharge temps. A Sporlan Y-1037 or Copeland demand cooling system will reduce the suction vapor temperature, which in turn will reduce the discharge temp. Without one of these, continue to expect mineral oil decomposition and contamination issues.
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