moisture in system.. this ? always sparks good conversation..

[ndk1911]

Can anyone prove or disprove whether a system(especially containing POE oil) can collect moisture due to a positive pressure leak??

Ex. Medium temp refrigeration system using R-22 w/ POE oil(pressures obviously never even get close to a vaccum) tests positive for high moisture in oil. System has many small leaks, but has never been opened up for a repair.. Im referring to the possibility of the oil in the system collecting moisture as it runs, not the possibility of some idiot throwing a gauge full of air on the system.

[jpsmith1cm]

I've heard of it, but am unable to offer concrete and documented proof of it.

The concept is a poorly timed and located Venturi due to a leak. High velocity refrigerant creates a negative pressure zone that allows moisture into the system.

I'm far more inclined to believe that there is another explanation.

[zw17]

I could see it happening but I am willing to bet you would pick up far more non condensables first and would see those issues long before you would see moisture problems.

Unless the pipe was submerged.

[bunny]

Always possible that the moisture was present in the POE and introduced that way.....POE does, after all, have a love affair with water.

[jpsmith1cm]

Always possible that the moisture was present in the POE and introduced that way.....POE does, after all, have a love affair with water.

Much more likely.

Evacuation doesn't remove moisture from POE.

You need driers to do that.

[RuralSpaceman]

No way. I wouldn't believe that even if the unit somehow ran under water.

Moisture has a mass and it moves by force like everything else. Until the forces equalize, moisture will stay where most convenient.

[Tech it out]

No way. I wouldn't believe that even if the unit somehow ran under water.

Moisture has a mass and it moves by force like everything else. Until the forces equalize, moisture will stay where most convenient.

Same thing I was thinking, but what do I know? Been doing resi all my life.

[jpsmith1cm]

Do either of you understand Bernoulli's Principle?

Also known as the "venturi effect"

http://en.wikipedia.org/wiki/Bernoulli's_principle

Study up.


I believe that it is possible, but would be extremely difficult to document and prove.

[RuralSpaceman]

Yes I remember Bernoulli's Principle from my industrial gas fitter's course, but I'm not sure it applies in a case like this. I can't think of any part of a refrigeration system that would form a venturi effect sufficient to overcome the force of escaping gas.

[LsT-Heating]

Do either of you understand Bernoulli's Principle?

Also known as the "venturi effect"
http://en.wikipedia.org/wiki/Bernoulli's_principle

Study up
I believe that it is possible, but would be extremely difficult to document and prove.

Tranes without LPCOs and the "Green Slimer" when pressures get low. It does happen, in very specific circumstances. On resi gear, you can't place enough suction/LL dryers to clean that mess up. R11x and ERPing was trane's SOP during that rash.

[timebuilder]

1) Yes, a venturi can form and draw air with moisture into a system.

2) Yes, the moisture can already be in the oil, unless it is carefully contained and kept from exposure to moisture before it is placed into the system. POE is extremely hygroscopic.

3) Now, from what I have been told, a dryer cannot remove moisture from POE oil. In mineral oil, the moisture is merely entrained with the oil. In POE, the moisture bonds with the oil chemically, and that makes it virtually impossible for a passive dryer to remove it. At least, that's what I was told. I may be wrong.

[jpsmith1cm]

I was told that a drier is the only way to remove moisture from POE.

You won't remove it with a vacuum pump, that's for sure.


There are also issues with water causing chemical changes in POE oil and causing it to revert back to its component chemicals, namely acid and soap.

Plugged cap tube, anyone?

[timebuilder]

I was told that a drier is the only way to remove moisture from POE.

You won't remove it with a vacuum pump, that's for sure.


There are also issues with water causing chemical changes in POE oil and causing it to revert back to its component chemicals, namely acid and soap.

Plugged cap tube, anyone?

It will be interesting to learn more about this. We have a very small number of RTU's that use POE, so this is not an issue for us right now. Maybe I'll try to research the dryer aspect some more when I have time.

[Chuck]

Bernoulli's Principle only applies if the velocity inside the pipe that has a small hole is so high that it starts drawing air into the hole and not letting any refrigerant out.

Lets just take a low temp running R404a with a -15 evap temp, 20 psig, and a small hole in the suction pipe. The velocity would have to be extremely high to ever reverse the 20 psi gas leaving the pipe and start drawing in air.

For a leak to leak gas out and suck gas in at the same time is completely impossible. You either have to take the pressure inside the pipe down to negative, or get the velocity so high it would create a slight vacuum at the leak(not gonna happen in a refrigeration system, velocity would never get that high). Maybe if you got the pressure down to .5psig you might have enough velocity to suck a little air in, maybe.

Urban Legend.

The more likely cause of getting moisture into a system would be having a leak in the low side and some intermittent restriction causing negative pressures at times, or a pump down system that is pulling down into a vacuum due to pressure switch set wrong.

[jpsmith1cm]

Bernoulli's Principle only applies if the velocity inside the pipe that has a small hole is so high that it starts drawing air into the hole and not letting any refrigerant out.

Lets just take a low temp running R404a with a -15 evap temp, 20 psig, and a small hole in the suction pipe. The velocity would have to be extremely high to ever reverse the 20 psi gas leaving the pipe and start drawing in air.

For a leak to leak gas out and suck gas in at the same time is completely impossible. You either have to take the pressure inside the pipe down to negative, or get the velocity so high it would create a slight vacuum at the leak(not gonna happen in a refrigeration system, velocity would never get that high). Maybe if you got the pressure down to .5psig you might have enough velocity to suck a little air in, maybe.

Urban Legend.

The more likely cause of getting moisture into a system would be having a leak in the low side and some intermittent restriction causing negative pressures at times, or a pump down system that is pulling down into a vacuum due to pressure switch set wrong.

We need the Mythbusters!!

[PMARS2345]

Check out this video on YouTube of a guy pulling a vacuum on a clear bottle of POE that came out of a new scroll compressor. http://www.youtube.com/watch?v=NzXO8...e_gdata_player

[jpsmith1cm]

Check out this video on YouTube of a guy pulling a vacuum on a clear bottle of POE that came out of a new scroll compressor. http://www.youtube.com/watch?v=NzXO8...e_gdata_player

Means nothing.

Yes, some moisture came out of the oil.


After he's done, send that stuff out for an analysis and see what the moisture content is.

You'll be in for a surprise.

[PMARS2345]

Quite a few statements on Poe oil here, any references to back then up? I'm nottt doubting what is said would like more info for learning?

[jpsmith1cm]

http://sporlanonline.com/November%20...Cold%20WAR.pdf

There is a start.

There are many, many threads here on this topic. Use the search feature.

[PMARS2345]

Thanks