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Old 02-13-12, 01:26 PM   #21
dcx
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Quote:
Originally Posted by TomWS View Post
Let me see if I understand.

Even if I use compressed atmospheric air (not specially dried) to pressure test the lines, since there is so little volume in the linesets, I won't be introducing a total amount of H2O that is outside of specification?

Further, if I then vacuum the lines to 500 microns (or, at least, below the vapor pressure of water), then the bulk of even that limited amount of water will be removed from the linesets?

Tom
Vacuuming the installation tubing below 500 microns will forgive you all sins you have done before it (air-pressure test).

Purging only by BBQ will leave acc. to calculation 0,2mg H20 inside the pipeline + H20 ,which is attached to the inside pores of the Cu tubing (impossible to now the quantity => heat treatment of the tubes prior installation undrer shieding gas would chase away the traces of H2O from pores).This is a DIY-man`s approach if vacuuming gadgets not available.A dryer in the circuit , however, is an exellent remedy for that.

Using vacuum you always know afterwards ,how much humidity left in the installation pipeline. You may have done exellent job in vacuuming ... but ...
there is a wet junk-yard called POE-oil in the system.You may only hope that the discharge line temperatures stay below acceptable levels (<+110degC).Otherwise overheated POE-oil turns partly into acid and water.
And then you have hell loose in the system.

If there is not "too much non-condensables" (or for ex.slurry blocking the streamer at MD) in the system , too high discharge line temperatures should not be a problem,I guess.I am not pretty familiar with this area ...

My point is that vacuuming is like shooting a mosquito by missile ... as a DIY-man I would think of other options as well!

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Old 02-13-12, 03:25 PM   #22
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Originally Posted by dcx View Post
<snip>My point is that vacuuming is like shooting a mosquito by missile ... as a DIY-man I would think of other options as well!
If the US DOD can shoot mosquitos with lasers, I can certainly go along with sucking out the moisture!

Actually, this was the point of my OP. IF I do plan to vacuum, is it safe to use compressed air for pressure testing? Both of these are easy for me to do with existing tools. Even using BBQ LP would require new fittings, but is not too unwieldy. Using other gases becomes increasingly more 'application specific', requiring more investment, making them less desireable to me.

As an added bonus, however, was the discovery of the fittings you pointed out! I am really looking forward to trying these!!!

Thanks again.
Tom
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Old 02-14-12, 01:00 PM   #23
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If you are prepared to Vac to 500 Microns or lower, you can use water to do your leak test if you really want. The beauty of using a liquid is a leak becomes apparent _really_ fast as a drop means a massive pressure difference.
The idea of using water to pressure test HVAC equipment gives me a queezy feeling in my stomach. What with all the effort to keep water out of your refrigerant, your compressor oil, your manifold gauge set, your vacuum pump oil, etc... and then to fill your target equipment with water to do a pressure test?

On another track, wouldn't water have a much higher viscosity than (any) gas? Woudn't the gas-&-bubble technique show up problems much, much faster?

I would think that a dry gas purge would be at the very top of the list of preferred purge media.

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Old 02-14-12, 02:04 PM   #24
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Originally Posted by AC_Hacker View Post
The idea of using water to pressure test HVAC equipment gives me a queezy feeling in my stomach. What with all the effort to keep water out of your refrigerant, your compressor oil, your manifold gauge set, your vacuum pump oil, etc... and then to fill your target equipment with water to do a pressure test?
<snip>
I'm virtually certain that BradC had his tongue firmly planted in his cheek when he made that suggestion. At least that's how I took it and he made his point, reinforced by dcex, that vacuuming to a very low pressure will forgive a lot of sins... almost including the mortal sin of pumping water into your lines.

Tom
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Old 02-14-12, 03:41 PM   #25
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Yeah Tom, that was my impression also.

I noticed the large plastic (screw-in) line-set caps on my first install didn't really seal down tight to the flare..
It's really just a dust cover. So, my line-set was likely pretty well loaded with moist air.
Right from the factory in China.

The Push-in plastic caps don't do much better at keeping down sea air infiltration.
Having the line-set sealed inside a plastic bag is a very good idea.

So, the vacuum operation is pretty dang important..


My point is:
When you unroll your brand new line-set, it would be okay to blow some dry air into into one end,
just make sure there wasn't any metal debris inside..

Any moisture left in the air inside the lines when you start your install,
should probably be flushed out a bit using your dry test gas (Nitrogen or Scuba air),
before tightening up the flares for the pressure testing. (Followed by vacuuming)..

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