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Flushing Refrigerant Lines


Is flushing refrigerant lines always necessary?

Most technicians and business owners I speak to say yes, especially when replacing R-22 equipment with R-410A equipment and you're reusing the old refrigerant lines. My response is always the same; since when?

This leads to the person listing the many reasons a thorough flushing is not only good, but required, like-

a flush kit removes acid, sludge, moisture, residual mineral oil; basically all the "bad stuff"in the old refrigerant lines.

They then go on to tell me how the new refrigerants and POE oils have problems with acid and moisture, and how in the "good old days" you could flush lines with R-11.

Really? I was around in the "good old days" and I never once flushed a refrigerant line with anything.

I've had refrigerant systems go aquatic when a chiller cooler ruptured. I've had fifty ton split systems burn so badly the suction line looked like a diesel tail pipe. Not once did I flush a system with R-11.

Now, about the statement "POE oils and R-410A have problems with moisture". Are you kidding me? ALL refrigerant systems have problems with moisture. In fact, you wouldn't have moisture in the system in the first place if you followed basic service procedures.

What do I use to remove moisture, acid, and sludge? The same thing most people used in the "good old days", a vacuum pump and a filter drier, and if the contamination was bad enough, we'd change the oil in the compressor.

Some people will tell you that a vacuum pump cannot remove moisture from POE oil, and they're right, but it couldn't remove it from mineral oil all that well either, just for a different reason.

Everyone knows that POE oil bonds with water on a molecular level, and a filter drier is the only way to remove it. Well, a vacuum pump can remove moisture from mineral oil, but it takes a very long time because the moisture has a hard time "breaking through" the surface tension of the oil. In reality, the filter drier did most of the moisture clean up for R-22 systems. Besides, the majority of the oil is in the compressor, and you NEVER run flush through a compressor.

What about cleaning up the residual oil and other gunk in the lines?

I always blew the lines out with C02 and had someone hold a rag over the other end of the pipe to catch the small amount of crud and oil that would come out. Notice I said "small amount"; if the refrigerant lines are installed properly, there should not be any low areas to hold excess oil or crud. If there are dips, and low lying areas, fix them! It may be part of the reason the original system failed.

To summarize- in my opinion, the best way to combat system problems is to use standard refrigeration practice to keep systems clean, and use standard refrigeration practice to clean them.


+1 # Bob Scaringe 2012-12-06 00:32
When you talking about moisture and the old days you missed a very important point: Mineral oil has a water saturation limit of about 25 Parts Per Million (PPM) but POE oil has a saturation limit of 2500, that is 100-times more water. Moisture is much more of a problem today than the old days. For reference, new refrigerant is suppose to have less than 10 PPM water. Also new HFC refrigerants and POE oil can't form corrosive mineral acids (inorganic acids) like the old refrigerants and oils. The only way you get these harmful acids in new HFC/POE or HFC/PVE systems is if you left them in there from using old line sets. Change the line sets or flush them if you can't change them. Sorry to tell you that the good old ways don’t work on today’s refrigerants and oils. Even sorrier if you don’t believe me.
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0 # Zenmaster 2012-12-06 08:29
Thanks for the input Bob.
Your statement about POE oil's love of moisture and the need to eliminate acid are correct but, flushing / changing the lines has nothing to do with controlling moisture; a tight, evacuated system with a filter drier is the only way to ensure no moisture.
I agree, new lines equal no sludge.
If you like using a system flush I would be sure to use it as directed, dispose of it properly, and check with the equipment manufacture first.
Sludge and acid caused problems for R22 and mineral oil like it does for 410a and POE oil.
Yes, back in the day, some used R11 for flushing; most didn’t, at least not where I’m located, they cleaned systems by changing the liquid line drier.
Why did it work? Refrigerant is a solvent, we let the system charge do the work for us, we just used a drier to collect the crud it cleaned up.

Remember: Nothing eliminates the need for proper service procedures.
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-1 # mike 2013-02-17 07:37
What about Friedrick Vert-I-Pac units, there isn't any room for firlter driers
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+2 # patrick peterson 2013-02-23 22:02
I'm curious, what do they recommend?

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0 # cnatrainingclass.com 2014-06-02 15:38
I like it when folks come together and share opinions. Great blog, stick
with it!
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