Compressor oil question...

[smoke]

After losing my battle with the Search engine...

So I'm working on a 40' walk in box with a Copeland semi-hermetic set up as a freezer. It's an R22 unit. Mineral oil, right?

So I had my boss send me some compressor oil for this unit, what shows up is some of our Thermo King POE oil.

-I have been reading that it's ok to run POE oil with R22. Is this true?

-In doing so, I'm guessing I would have to completely change out the oil, as in not mixing the two (topping off with POE)?
Good thing they sent me 1 liter of oil...


I think what happened is he asked one of our techs to send it and this is what I got. I also asked for the pump and I ended up with a condensate pump motor for a ceiling mount split pack.


~smoke~

[craig1]

Unless you love cleaning txv screens and changing plugged filters don't do it!!!

Putting POE in an R-22 freezer that has run on mineral oil will put you in a world of pain.

[sammyray]

POE oil mixed with mineral oil can cause wax in metering devices.

[smoke]

both great replies!

Thanks guys. My gut was telling me these would be the issues. It's nice to have those that have been down that road confirm it before I go down that path.


Cheers,

~smoke~

[craig1]

The big issue with r-22 freezers is that they burn the oil and coat the lines with carbon. POE is an excellent solvent and it causes the carbon to break loose and plug up everything

[Phase Loss]

POE oil mixed with mineral oil can cause wax in metering devices.

Can you show documentation on this? I would be very interested in reading something about that.

[stanbyyourword]

its more theissue of becoming solvent and letting loose years of internal gunk. as far as I know the wax is only attributed to overheat conditions? stan

[Phase Loss]

take this for what it's worth

**assuming your system actually needs oil**

My opinion is...go ahead and mix the oils.

R-22 is an HCFC. That means it is compatible with Mineral, Alkylbenzene, & POE
Which means the R-22 is fully miscible and soluble with all of the above oils.

You would not want to mix oils if you were using a HFC refrigerant E.G. R-404, 507, 134...These refrigerants are IMMISCIBLE and INSOLUBLE with Mineral & Alkylbenzene. This means that the oil that has traveled to the evaporator will separate from the refrigerant into two distinct phases. This will reduce heat transfer and rob the compressor of its much needed oil. HFC's require POE.

It is true that low temp R-22 inherently runs high discharge temperature which can cause carbonization of the oil. And POE does act as a cleaning solvent. which will scrub the pipes clean possibly leaving you with plugged filters/screens.

But it is also true that if you maintain proper compressor superheat, keep a clean condenser and low compression ratios that low temp R-22 will run discharge temperatures will below the carbonization limits.

Mixing oils does not create wax in the system. If you're system is running mineral oil, the wax is already in the system (mineral oil naturally has wax in it) and the only way that the wax will separate from the oil and cause restrictions is in very low temp refrigeration. If you get the oil too cold, down to around -70* you will loose your miscibility and solubility and cause the wax to separate from the mineral oil.

I say go for it! worst case scenario, you gotta change the liquid filter if your system has a lot of burnt oil due to poor maintenance.

[jpsmith1cm]

Can you show documentation on this? I would be very interested in reading something about that.

As I understand it, there is a grain of truth to this.

POE oil will not dissolve wax like mineral oil would.

When you introduce POE into an already waxy system, then the was can no longer be held in solution by the mineral oil and it precipitates out.

So, it doesn't CAUSE wax, but it can REVEAL it.

[jpsmith1cm]

Oh, and a portable refractometer will reveal exactly what oil is in the system as will an oil analysis.

Refractometer is more expensive, but you will have it on the truck for future use.

[Phase Loss]

i don't buy it until I see some documentation that can clearly state that mixing oils will create/reveal wax issues.

The wax will separate in MIN oils due to low temperatures. its inherent in nature. MIN is not even preferred in LT applications because of it. It's much more advised to use synthetic oils like Alky or POE in LT because they are made without wax

here is a Copeland approved oils PDF that even shows and acceptable mixture of POE & MIN

But I am certain if mixing oils created wax issues, Copeland would not recommended it

[jpsmith1cm]

http://www.google.com/url?sa=t&sourc...yWnRQ_lE149dJQ

Not the document I'm thinking of, but the last page refers to the phenomenon I was talking about.

And it is hard to argue with Rob Yost.

[Phase Loss]

ah yes, but that's talking about someone adding "mineral oil material" into a HFC system. Not talking about adding POE to it. POE is far from "mineral oil material" mineral oil is IMMISCIBLE and INSOLUBLE with HFC's

I agree, RobY is a smart cookie on oils

here are some links of him mentioning how mixing POE and MIN is not only not a problem, but in fact improves the miscibility when done so in HCFC's especially low temp.

which pertain more to the OP as he is wondering about HCFC R-22 and not HFC's

http://hvac-talk.com/vbb/showthread.php?t=78710&page=2
http://hvac-talk.com/vbb/showthread.php?t=106933
http://hvac-talk.com/vbb/showthread.php?t=143573
http://hvac-talk.com/vbb/showthread.php?t=144733
http://hvac-talk.com/vbb/showthread.php?t=145681