Something in refrigerant oil

[BennyD]

Just swapped a compressor on a scroll chiller. Started evacuation after a pressure test and found this in the sight glass...
It looks like liquid travelling up! This was factory charged with oil and still under pressure when I pulled the plugs. The evap was at room temp when we pulled it apart.
I was at around 900 microns when that video was taken so I'm not so sure it was water and the vacuum pump oil was still clear. Maybe cleaning solvent?
Any suggestions?
https://youtu.be/y-9L8bfMs54

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[BennyD]

Ok, after looking at my video again, I'm starting to feel kinda stupid....
It looks like a clear cover over the motor wires with bubbles running up inside of it.
When I first saw it, I thought it was on the OUTSIDE and wondered why it was moving so slow.

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[coolerik]

Sou figure it was just nitro stuck in the insulation of the motor wires/windings? Weird one for sure....


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[itsiceman]

Sou figure it was just nitro stuck in the insulation of the motor wires/windings? Weird one for sure....


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The gas is coming out of the oil

[coolerik]

The gas is coming out of the oil

So nitrogen entrained in the oil? Or is the oil itself “off gassing”?


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[itsiceman]

N2 and H2O would be my guess

[coolerik]

N2 and H2O would be my guess

But I thought you can’t get moisture out of POE...


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[itsiceman]

But I thought you can’t get moisture out of POE...


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Sure you can. Vacuum works it just takes a long time compaired to other ways.

You know maybe its mostly H2O at lower vacuum since the bubbles seem to mostly originate from the bottom whenever I'm watching.

[Robber]

That brings up a thought I had about water and oil in a compressor. Ok so atmospheric pressure is 14.7 PSI and you pull a vacuum down to a few hundred microns to remove water. If the water is on the bottom of compressor ie oil on top of oil. The oil will add weight to the water below therefore it won't evaporate because the pressure is above the saturated point. So what is the weight of refrigerant oil per inch as it compares to the Micron scale??? Or said phrased simpler how much more vacuum do you need to boil water at lets say 60 degrees when it under the oil compared to sitting exposed in the lines.

[BennyD]

I'm guessing it's probably moisture that was still in the oil boiling off up through a clear piece of insulation. Kinda freaked me out at the time.
I'm sure there is a way to figure out when moisture will boil out underneath the oil. Just thinking, it would probably have to deal with ambient temperature, the specific gravity of the oil and the depth.

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[itsiceman]

If you add heat I know it speeds up

[BennyD]

If you add heat I know it speeds up

Much more than one would think! I usually try to get the CCH going if it has one before I evacuate. Have used a heat gun if time is of the essence...

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[BBeerme]

Why wouldn't it be nitrogen forced into the oil that was 'boiling' off? That would be my first guess.

I'm guessing it's POE oil (?).

Here's something interesting that happened a week and a half ago. I get sent to change out a compressor because this will be a warranty call on us. New account. Customer told us not a good history. So there is no way I'm going to leave this compressor running after initial start up without me being right there.

As chance would have it, running down to the truck to get something then back up to the roof, took a half hour. Probably got a couple of phone calls answering questions from the office or other techs. Anyway, when I left the roof, the oil was at the bottom of the sight glass. When I went to start it up, the level was over the top of the sight glass.

In just half an hour, so much refrigerant migrated to the oil, that the level raised that much!

Although I did just shut the unit down when I walked away from it, the crankcase heater was bad.

So, if that much refrigerant can migrate into the oil in only half an hour, how much nitro do you think can be absorbed by that same oil in a month or two? Or more.

I'm guessing it's probably moisture that was still in the oil boiling off up through a clear piece of insulation. Kinda freaked me out at the time.
I'm sure there is a way to figure out when moisture will boil out underneath the oil. Just thinking, it would probably have to deal with ambient temperature, the specific gravity of the oil and the depth.

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[71CHOPS]

Looks like a clear dip tube.....maybe for an oil pump?

could be nitrogen entrained in the oil.

[BennyD]

First, it's mineral oil.
Second, I'm not so sure it could be nitrogen, at least not at those pressures. I think the material the gets in the oil needs to be in an environment to be capable of being a liquid?
If there was nitrogen in the oil, I think we would see it well before the boiling point of water.

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[71CHOPS]

First, it's mineral oil.
Second, I'm not so sure it could be nitrogen, at least not at those pressures. I think the material the gets in the oil needs to be in an environment to be capable of being a liquid?
If there was nitrogen in the oil, I think we would see it well before the boiling point of water.

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oil will absorb and retain a certain percentage of refrigerant......it will retain that percentage regardless of everything happening around it.....vacuum, pressure, etc. it can be removed, given a long enough vacuum, or distillation process. but in the short time of a 500 micron evacuation, I don't think it will separate.


There are always pockets of refrigerant and oil left out in the system after recovery. that fresh oil could have absorbed it's small percentage from the rest of the system during the evacuation......I dunno….seems unlikely, but it's possible.


I think a more likely explanation is that the fresh oil in the crank case was sloshed around during transport and installation, causing air, and/or nitrogen to be mixed in and trapped under the surface...….the evacuation is removing it.

[BennyD]

Now if there were nitrogen bubbles trapped in the windings that never made it to the surface. I could see them expanding under the low pressure and finding a way up.

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[itsiceman]

oil will absorb and retain a certain percentage of refrigerant......it will retain that percentage regardless of everything happening around it.....vacuum, pressure, etc. it can be removed, given a long enough vacuum, or distillation process. but in the short time of a 500 micron evacuation, I don't think it will separate.


There are always pockets of refrigerant and oil left out in the system after recovery. that fresh oil could have absorbed it's small percentage from the rest of the system during the evacuation......I dunno….seems unlikely, but it's possible.


I think a more likely explanation is that the fresh oil in the crank case was sloshed around during transport and installation, causing air, and/or nitrogen to be mixed in and trapped under the surface...….the evacuation is removing it.

It was a new compressor

[itsiceman]

First, it's mineral oil.
Second, I'm not so sure it could be nitrogen, at least not at those pressures. I think the material the gets in the oil needs to be in an environment to be capable of being a liquid?
If there was nitrogen in the oil, I think we would see it well before the boiling point of water.

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Ok..... What new compressor comes with mineral oil?

[BennyD]

Don't Trane scrolls come with OIL15…
Edit: For R-22
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