Nitrogen pressure...how much?

[kritic]

When you guys run nitro thru a system, in this case thru the liquid line, thru txv,thru evaporator and out suction line how much pressure do you normally push it at and for how long.:confused:

Thanks

[Kevin O'Neill]

Use as little pressure as possible. If you put it in the liquid line at the outdoor unit and take it out the suction line at the outdoor unit, put the hose attached to the suction line port near your face, you should barely feel the flow. If the pressure is high enough to show on your gauge, it will blow the joint out as you solder it.

Better yet is to buy and use a flowmeter. Set it for a few cubic feet per hour. You may want to purge hard while you are setting up to make sure all air is out of the piping, but while brazing you want the pressure and flow to be as low as possible to prevent joint blow out.

[gregp]

We teach our guys to purge the system with @ 1-2 psig when brazing, and no more than 150 psig when leak testing. Anyone doing it differently?

[mark beiser]

I recommend you run it in the suction line and out through the liquid line, and remove the cores from the service ports.

Running it in through the liquid line and out the suction line yields poor results on a system that has a non bleed TXV in the indoor coil.

Once you sweep the lines out a little, all you need is just a little bit of a positive flow. Crank your regulator pressure way down, and just barely crack the valve on your service manifold so you can just barely feel it coming out of the service port with the back of a wet finger. More than that and you are just wasting nitrogen.

[kritic]

ok I guess I didnt specify but what im wanting to do is clean the system out or purge it not doing any brazing at this point so do I still use 1-2 lbs for a clean out or do a harder flush

[big johnson]

ok I guess I didnt specify but what im wanting to do is clean the system out or purge it not doing any brazing at this point so do I still use 1-2 lbs for a clean out or do a harder flush

What do you mean by cleaning the system out? Are you trying to get air or contaminants out? If so, pushing nitrogen through it ain't gonna do ya much good, unless you're talking about tripple evacuation.

[kritic]

yea I just want to shoot some nitro thru it knowing that its not going to clean out as well as shooting some kind of flush into it, but this system has set for a while and im replacing the outside unit only. Did not have compressor burn out. Just wanted to shoot some nitro thru it to purge it and was wondering at what pressure would I do that at:o


Thanks

[ar_hvac_man]

I wouldnt go any higher than the pressure at which the factory tested at. I think they test with about 250 lbs.

[gregp]

did this system "set for a while" with refrigerant in it, or was it empty and open to the atmosphere? And is it R-22 or R-410A? Just wondering.

[davefr]

yea I just want to shoot some nitro thru it knowing that its not going to clean out as well as shooting some kind of flush into it, but this system has set for a while and im replacing the outside unit only. Did not have compressor burn out. Just wanted to shoot some nitro thru it to purge it and was wondering at what pressure would I do that at:o


Thanks

I'm curious what good this does?

Nitrogen is used for pressure testing, brazing shield gas and breaks the vacuum during a triple evacuation.

Just blasting Nitrogen thru the lines doesn't seem like it would accomplish anything by itself other then to purge air from the lines. However that's what vacuum is for along with boiling off any moisture.

[kritic]

Well here is why I was going to do it. Had 1 of my instructors from a couple of years ago just recently when I told him what I was doing told me to blast some nitro thru it, also the lennox dealer where I bought the system ask me if I had nitro and I said yes and then he said good just shoot some thru it before installing but I never knew at what pressure so thats why I asked evidently know one here does it except for brazing issues.:eek:

[kritic]

The system is not open to the atmophere and is r22. In fact that was the first thing I checked and it does have refrig. in it.

[njaircond]

Uses flash the system from the suction line in low-pressure not damaging the unit expansion valve
njaircond working on repairing subzero in New Jersey the refrigeration unit has capillary tubing so it's not danger to exceed the high pressure that is about 200 psi john http://www.njaircond.com

[davefr]

Uses flash the system from the suction line in low-pressure not damaging the unit expansion valve
njaircond working on repairing subzero in New Jersey the refrigeration unit has capillary tubing so it's not danger to exceed the high pressure that is about 200 psi john http://www.njaircond.com

^^^^^ What's he saying??^^^^^

[kritic]

lost me too now im really confused:confused: :confused: :confused: :eek:

[ar_hvac_man]

Uses flash the system from the suction line in low-pressure not damaging the unit expansion valve
njaircond working on repairing subzero in New Jersey the refrigeration unit has capillary tubing so it's not danger to exceed the high pressure that is about 200 psi john http://www.njaircond.com

My pig-latin is rusty. Do what now?

[docholiday]

Blowing nitorgen through a system doesnt clean anything out. If you need to flush a coil and lineset then you need a "flushing" product.

[jasond1011]

whenever i have a burn out or when i replace a compressor or a condensor i pull the cores and force as much pressure as i can build two to 300 pounds into liq line and hold my thumb over the open suction line by the time your finger comes off you can usually get a huge slug of oily goo from trap underground from years of oil settling. especially after several compressors. i blow it both ways. lots of times nothing but i have gotten two pints of oil and nasty crap out of some lines . YES these were lines that were not replaceable or i would have, but yeah if you think you got sludge in there it can save a plugged drier. especially if some yo yo didn't put in a liquid line drier when the comp took a dump.if possible we like to weld in a suction line burnout drier outside the cabinet and wire the heat pump for cool only then go back a few weeks later and cut it out to protect new condensor .then reconnect reversing valve.

[rheem n u]

if you have nitrogen flowing its kinda hard to tell what pres you are at unless u have a flowmeter.

[4l530]

Originally posted by njaircond
Uses flash the system from the suction line in low-pressure not damaging the unit expansion valve njaircond working on repairing subzero in New Jersey the refrigeration unit has capillary tubing so it's not danger to exceed the high pressure that is about 200 psi john

Its a spambot. :mad:

[Wheelbaron]

OK, this may sound like a dumb question, but why are you guys all using nitrogen while brazing? Is this something you do on large lines to keep from oxidation on the inside of the line? Or is this just an attempt at avoiding leaks? I work on a lot of small stuff, 1/2" or less most of the time. The only time I ever use nitrogen while brazing is when I have a coper to steel fitting at the compressor high side. I really hate it when you burn off the damn little 1 inch of tube they give you to braze too, then you have to sit there and try to fill in the hole with brazing rod without putting a hole in the compressor shell. Of course this always happens late in the evening out in the middle of no where on a weekend with a cold box full of product that is quickly going bad in the 90 degree July heat, and the mosquitoes are so thick you can hardly see what your doing....:o

[ar_hvac_man]

[QUOTE=Wheelbaron;1416208]OK, this may sound like a dumb question, but why are you guys all using nitrogen while brazing? Is this something you do on large lines to keep from oxidation on the inside of the line?

All lines. The black crap that is on the outside of the lines after brazing will also be on the inside if no n2 is used.

[Wheelbaron]

True, but for one thing I don't realy get much oxidation on small lines, and two, isn't that why we put on filters in the first place, to catch things like carbon partials? I use cap tubes down to BC1, and the only times I ever get plugged tubes is from that damn **** R-134 A, I use MP 39 (R 401-A) and I don't get any problems. Have I been doing this all wrong for for six years? I will try to start getting into a practice of using Nitrogen from now on. Also I have gone up to 300 psi once or twice trying to find an elusive leak. Most of my units take about 13 oz of refrigerant and one micron per hr leak can cause me a lot of trouble. :eek:

[jasond1011]

are you using 45 percent and dampened flux on those steel to copper joints or 15 percent? i have always used 45 percent only on steel to copper and a little water in the paste flux bottle so the brush can pick up a good paste. clean parts and good feather on the torch and the joints are beautiful. using 15 percent is tough to do on steel and copper. well worth the investment and a little roll last a long time.

[mark beiser]

I flow nitrogen regardless of if it is a small dehumidifier that holds less than a pound of refrigerant, or a 40+ ton split system.
The only difference is that I get a much bigger bottle for the big systems. ;)

[ndfrozen]

I recommend you run it in the suction line and out through the liquid line, and remove the cores from the service ports.

Running it in through the liquid line and out the suction line yields poor results on a system that has a non bleed TXV in the indoor coil.

Once you sweep the lines out a little, all you need is just a little bit of a positive flow. Crank your regulator pressure way down, and just barely crack the valve on your service manifold so you can just barely feel it coming out of the service port with the back of a wet finger. More than that and you are just wasting nitrogen.

I usually "wet the back of my hand" as this seems to be the most sensitive part that I have easily avaliable to use.:D

[alpha480v]

We teach our guys to purge the system with @ 1-2 psig when brazing, and no more than 150 psig when leak testing. Anyone doing it differently?



That's what I do.

[mikelcs]

We teach our guys to purge the system with @ 1-2 psig when brazing, and no more than 150 psig when leak testing. Anyone doing it differently?

why 150 psi? that is a little low in my opinion. we go a minimum of 300 for leak test.