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Old 02-10-12, 08:48 AM   #1
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Default Pressure Test Mini Split with air instead of Nitrogen?

I'm going to be installing two mini split heat pumps for my workshop and wonder if air can be used to pressure test instead of nitrogen?

My reasoning is that the line sets are open to the air during installation and then all of the gas is purged during vacuum pumping anyway, what's the risk of using compressed air pressure instead of Nitrogen for leak testing?

Tom

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Old 02-10-12, 11:09 PM   #2
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it puts moisture in your system you should purge it with low pressure untill your ready to charge it your filter dryer asorbs moisture as does the oil in the compressor compressed air has lots of moisture close up all ends asap moisture kills ac systems
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Old 02-12-12, 01:31 AM   #3
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Quote:
Originally Posted by TomWS View Post
I'm going to be installing two mini split heat pumps for my workshop and wonder if air can be used to pressure test instead of nitrogen?
I installed my mini-split.

My units came pre-charged... the charge was all in the outside units. I hooked up the line set per the instructions, and used assembly lube on the threads and faces of the flair fittings. Then I torqued the flair nuts on per the installation instructions. I used a torque wrench to do this. I didn't have a crow's foot wrench that would fit my torque wrench, so I welded one up from an open-end wrench and a cheap socket. the required torque force was higher than I would have expected, so I'm glad I used the torque wrench.

Since you're not brazing anything, you should be good.

Still need to pull a good vacuum, though. Now I wish I had used a micron gauge so that I could tell that I was getting a good vacuum. I let my vacuum pump run for a couple of hours with fresh oil...

But it's now two years later and it's chugging right along.

-AC_Hacker
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Old 02-12-12, 07:21 AM   #4
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Quote:
Originally Posted by AC_Hacker View Post
I installed my mini-split.

My units came pre-charged... the charge was all in the outside units. .. the flair fittings. Then I torqued the flair nuts on per the installation instructions. I used a torque wrench to do this.

Still need to pull a good vacuum, though. -AC_Hacker
There are other choices available instead of traditional flare coupling ,as well.

=> LEAKAGE FREE SAE CONNECTORS ,where no wrench needed.
-Helium tight ... max. leakage He 0,5g /10years !
Question:Any need for pressure testing of the line?

Nut connection SAE

============================

Before my reincarnation as a human being(?) I made some simple calculations in terms of the reasonable moisture prevention since the modern mini-splits do not have any dryers!

The target was "how to avoid need of vacuuming" and still be on the safe side rgd. the max. moisture burden the system could swallow without long-term problems.

Below my calculations (not comissioned under influence of buse):

Assuming Rough H20 BURDEN in a commercial system of 2,5 .. 3,5kW as follow:

Original H2O in system in "standard state"
======================================
R410a 1000g => 10 mg H2O (max. allowed H2O 10 ppm)
POE-oil 300g => 15 mg H2O (... " ..... " ......... 50 ppm)

=======================================
Purging alternatives ... pipeline 2x7,5m=>volume 0,5 litres

Propane (R290) 0,5 litres => 1/100 mg H2O (max. allowed H2O 10 ppm)
Propane (95%) 0,5 litres => 0,2 mg H2O (max. allowed H2O 200 ppm)
--------------------------------
AIR 0,5 litres => 7,5 mg H2O (+15degC, 15g moisture in 1m3 of air)


There is the basic question left:
WHY on earth solely vacuuming recommended for the installation of Cu-pipelines,if they are dry ,bright inside and capped at opposite ends prior to installation?

The quantities of moisture in the installation pipeline after purging for ex. BBQ propane (95%) is only 0,2mg vs.max.15mg H2O drifting/cruising in POE-oil.

Eventhoug the purging is not 100% complete there is a lot of H2O "dryer-capasity" left in POE-oil before facing the allowed max. standard levels.As far as I know the moisture tolerance on the system level is as high as 100ppm for H2O.

The vaccuming itself is not 100% proof either!It could be done ok or very ok!

You may say there could be some unvisible moisture left in the pores of pipelines prior installation in spite of proper purging.VeryTrue!
This could be "easily" avoided by domestic means => the Cu-pancake coil into the stove/Sauna ... +>100degC or so (simultaneously under purging-mode to prevent oxidation, N2 is safer but BBQ is ok if you know what you are dealing with).And after that,flatten the ends of the the tubes (gas still inside) and go to your installation site!

PS:
The pressure test could be done by BBQ-gas as well.Only raise the temp in the tank upto +40degC => then you get abt. 15bar out!

Patent for this is pending ... de..pending on financing ...
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Old 02-12-12, 08:06 AM   #5
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AC_Hacker & DC-X, thanks for the response! I'm glad there are 'alternative' thinkers out there who challenge the accepted practice. While I'm all in favor of following the process if you've got the equipment, if you don't have a ready source of Nitrogen, it's time to ask, "Are there alternatives?"

I like your informative analysis, DC-X, it is extremely useful in getting a perspective on the problem. It hadn't occurred to me to use propane! I like it!

I will pull a vacuum, however, since I already have the equipment. I'm a woodworker and use vacuum forming for bent laminations.

I'm intrigued by the fittings you referenced. Have you used these? Considering that I'm a newbie when it comes to making flares, would you recommend these as an alternative?

Thanks again,
Tom
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Old 02-12-12, 09:41 AM   #6
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PS:
The pressure test could be done by BBQ-gas as well.Only raise the temp in the tank upto +40degC => then you get abt. 15bar out!
Err.. unless you plan on raising the temperature of your hoses and lineset to the same as the tank this is not going to work the way you think it will.

What will happen is as you raise the tank pressure gas will immediately start to condense in your hoses and lineset. This will continue until they are completely full of liquid, at which time the overall pressure will start to increase toward your desired test pressure.

You will then need to re-cool the tank below the temperature of your lines and hoses to allow the liquid to migrate back to the tank before disconnecting things.
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Old 02-12-12, 10:46 AM   #7
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Quote:
Originally Posted by TomWS View Post
I'm intrigued by the fittings ...... would you recommend these as an alternative?

Tom
YES!
Widely used in Europe by those who do not want to retighten the system tubing within 4-5 years or so due the Cu-deformation of Cu-flares because of system vibration and temperature changes.

http://www.armacell.com/www/armacell/ACwwwAttach.nsf/ansFiles/092-005-EN-UK-IRL.pdf/$File/092-005-EN-UK-IRL.pdf

see .pdf 4/4

http://armacell.si/www/armacell/acwwwattach.nsf/ansFiles/RangeArmaflexSplitIran.pdf/$FILE/RangeArmaflexSplitIran.pdf

Calibration tool not that necessary!
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Old 02-12-12, 11:39 AM   #8
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Err.. unless you plan on raising the temperature of your hoses and lineset to the same as the tank this is not going to work the way you think it will.

What will happen is as you raise the tank pressure gas will immediately start to condense in your hoses and lineset. This will continue until they are completely full of liquid, at which time the overall pressure will start to increase toward your desired test pressure.

You will then need to re-cool the tank below the temperature of your lines and hoses to allow the liquid to migrate back to the tank before disconnecting things.
My intension was only to give a choice for temperary/quick raise of pressure.
That time one could make the soap/foam-test for the system if one feel that is necessary when using those "Helium tight" connectors mentioned earlier.Using propane (BBQ) is not a good way to raise the pressure ,but it is one way when there is a lack of other options.

Instead of N2 ,Argon could be used as well but these have to be purged away afterwards or vacuumed!

When having traditional flare connection ,proper pressure test is a must!And retightening of nuts within forthcoming 5 years!

If the lines purged by propane ,only let the extra pressure leak out (into the well ventilated air) before tightening the nuts .It is not illegal.

Acc. to ARI 700 standard there may be 0,5% condensebles left (other than HFC) in the system , .pdf 19/24

http://www.ahrinet.org/App_Content/a...%20and%202.pdf
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Old 02-12-12, 04:46 PM   #9
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I'm enjoying this discussion!

Re Serto fittings, one thing I liked about them, in addition to not having to flare the tube, was the fact that the installation procedure simply calls to tighten 1 3/4 turns after hand tight for initial install - NO TORQUE WRENCH to fiddle with!

Re using propane for leak test and purge, I wasn't going to raise the temp to get 15Bar. To my mind, any reasonable pressure is good enough to leak test, the only advantage I see of a higher pressure is that it makes any leaks that much more obvious. I'm certainly not going to pressurize until it blows! If the tubing's holding 100-150 pounds, then it's not 'broken'... Plus, as you say, propane sounds like a real convenient purge.

Tom
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Old 02-12-12, 08:38 PM   #10
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My intension was only to give a choice for temperary/quick raise of pressure.
Fully understand and appreciate that, however I felt the need to explain *what* would happen in enough detail as to prevent anyone who was attempting the procedure copping a face full of liquid LPG when they disconnected the hose.

It won't take long at all for liquid to start to condense in your lineset (like by the time you get the pressure to your target point they will be pretty much full).

Quote:
Originally Posted by dcx View Post

Acc. to ARI 700 standard there may be 0,5% condensebles left (other than HFC) in the system , .pdf 19/24
Yep, and allowances are all well and good, but of course the more non-condensibles you have in the system the less space you have in your condenser and the less efficient your system will be. Also, the less moisture you have in the system the longer it will last!

Buy, beg or borrow a Vacuum pump (they are certainly cheap enough).

Now, I recently bought a *good* micron gauge. I used to whack my Vac pump on a system for a couple of hours to suck it down. With the micron gauge, I noted it took over 24 hours to vac a system down below 500 microns with 5' 1/4" hoses.

Now this is a 7KW ducted heat pump, so it's not a small system, but it does go to show that longer is better than shorter!

Please don't let me discourage you. Your input is truly excellent, I just wanted to finish painting the picture a bit more.

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