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Xringer · 10-11-11, 08:48 PM

If you look at the way a flare connection is assembled, it's design
allows for a vacuum to really suck the tubing flare down on the cone.
That makes for a very tight seal.

While testing with my test line-set, during my repair project,
http://ecorenovator.org/forum/geothe...html#post16037

I vacuumed out the line-set many times (with both Sanyo valves closed) and removed the test line-set later.
A few times, when I loosened the 5/8" flare nut, there was no hiss of air rushing in.
I had to pull the 5/8" tube off the cone, before the air rushed in..

That tells me that long duration vacuum testing on a line set that can get down under 200 microns is not very useful.
IMHO, If you can get down to <200 and maintain that with the pump running, 10 or 20 minutes (during warm weather)
should remove all the moisture from the line set.

So, looking at the flare connection design with 400 PSI of nitrogen inside the line set,
then you need tight flare nuts! That nut becomes very important.
The lack of any small defect on the mating face of the flare or cone become very important.

The nitrogen pressure test is more important! It simulates real world conditions. Pressure inside the line-set.

My only small worry is putting too much pressure in the line set, which might possibly
force nitrogen into one of the closed valves and into the refrigerant.

10-11-11, 08:48 PM	#439
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	If you look at the way a flare connection is assembled, it's design allows for a vacuum to really suck the tubing flare down on the cone. That makes for a very tight seal. While testing with my test line-set, during my repair project, http://ecorenovator.org/forum/geothe...html#post16037 I vacuumed out the line-set many times (with both Sanyo valves closed) and removed the test line-set later. A few times, when I loosened the 5/8" flare nut, there was no hiss of air rushing in. I had to pull the 5/8" tube off the cone, before the air rushed in.. That tells me that long duration vacuum testing on a line set that can get down under 200 microns is not very useful. IMHO, If you can get down to <200 and maintain that with the pump running, 10 or 20 minutes (during warm weather) should remove all the moisture from the line set. So, looking at the flare connection design with 400 PSI of nitrogen inside the line set, then you need tight flare nuts! That nut becomes very important. The lack of any small defect on the mating face of the flare or cone become very important. The nitrogen pressure test is more important! It simulates real world conditions. Pressure inside the line-set. My only small worry is putting too much pressure in the line set, which might possibly force nitrogen into one of the closed valves and into the refrigerant.