Brazing without nitrogen?!

ChrisJ

My boss had a split system installed yesterday and I noticed the guy was doing all of his brazing without flowing nitrogen. I asked him where his nitrogen was and he told me that is only used for pressure testing and is never used during brazing.



I'm a bit disgusted at this and am wondering how common of a practice this is?

bob_46

N2

Chris, from my 40 years experience working for a number of contractors I would say N2 is the exception rather than the rule . If you question the boss they usually tell you "that's why

they invented filters" ! The only jobs that used it consistently were medical gas jobs and chemical research .

ChrisJ

Interesting

Bob,



Thanks for responding. This is the kind of feedback I'm interested in hearing because I only do this for a hobby so I don't know what goes on in the real world.

RobG

Cost

Nitrogen costs more than O2. End of story. I guess that's why god invented filters.





I have a friend who owns a bar and has a long draw beer tap system. He has to use a nitrogen CO2 mixture to keep the beer from foaming (and wasting the nectar of the gods). It costs about twice what straight CO2 does, however that's still cheaper than wasting the beer. The almighty dollar wins every time.



Rob

Techman

Brazing

should be done using Nitrogen! You are right ChrisJ. Nitro is CHEAPER than FilterDriers, not using Nitro will eventually lead to a comp failure. Everywhere you see the oxidation marks on the outside of the tubing there will be matching oxidation/flacking on the inside of the copper tubing.



Back in the day air was used to pressureize the keg of beer, the last 1/4 of the keg tasted way different than the 1st 3/4 of the keg. The CO2 left the beer to fill up the atmosphere of the keg, then C02 was used to pressureize the keg, but the last1/4 of the keg was usually over CO2'ed and foamed up the mug. Then NuCO2 was brought in and much less foaming thru out the entire keg. Almost good to the last drop, for beer lovers.

ChrisJ

Cost

I think it costs me $20 or $25 to have my 60cuft bottle filled. Seems fairly cheap to me.

RobG

I wasn't

I wasn't disagreeing with the nitrogen brazing issue (I don't do A/C except my own and only with the help of a friend who DOES do A/C). I do however braze piping for plumbing work and just use oxy/acet. I don't have to worry about compressors, I just unscrew aerators. However allot of companies don't care. The customer pays for the filter, when the compressor does give up the ghost they are going to call the guy who's sticker is on the unit, them. Then they will sell them a whole new system. Once again, the almighty dollar wins. Unfortunately it is the mantra of allot of service companies.



Rob

Techman

Nitro.

For ACR that Nitro has to be "dry" or you will be adding wetness into the refrig system.

Paul S_3

nitrogen and brazing

When I worked for other contractors they never wanted me to braze with nitrogen, only to pressurize. On the other hand they had many problems with clogged TXV'S and failed compressors etc, that they had to go back(call backs) which cost money, now I have my own business all my techs and me and my partner ALWAYS braze with nitrogen purging through the line set, Johnstone sells a adapter especially for this purpose and a low psi regulator, I have very few call backs ,luckily.....Paul s

Ironman

A Slight Compromise

I almost hate that word, but some circumstances warrant it.



If it's a mini split system or multiple joints, then N2 should always be used. If it's just connecting the line set on each end (2 joints) with a properly sized filter/drier installed, then I don't see where there's enough oxidation produced to make a difference.



Just MHO, but in 40+ years, I don't know of a compressor failure that I've had in less than 10 years of service from a unit. Electrical and other component failures which would cause a compressor failure being excepted. It may even be closer to 15 years. I'm very meticulous and a leak free system, a good vacuum and proper charging are more important than a MINOR amount of oxidation.



Again, JMHO.

ChrisJ

Minor?

Are you sure it's minor?



http://youtu.be/3uP-eb8Zz08

gennady

nitrogen

When we did ac installations, nitrogen was a must. Triple evacuation only dries up copper, and testing shows the leaks. But brazing without nitrogen is a shortcut to lower costs. Anyway i heard that some plumbers do not use primer on PVC joints. so I'm not surprised.

Ironman

Video

Nice video; and it makes the point of the need for using N2. I'm not disputing that, but please look at everything I said.



I've worked on everything from 1000 ton centrifugals down to household refrigerators. I've seen a four inch suction line on a recip so full of carbon from a burnout that it filled 2 quart jars. What could not be removed by hand cleaning had to be left in for the driers to catch. They did just that and after the second change, remained clean.



I've seen centrifugal burn outs so bad that after chemical cleaning, the driers still required multiple changes. But they did their job and the compressor ran fine for many years thereafter. Don't discount what the drier can do.

jumper

this is why

Packaged unitary and chillers are bought.Even in industrial & high technology environment management does want to get into refrigeration assembly.

Techman

Brazing.

I agree with Ironman . Have done it , still do it and will continue to do it! Nice point ! But not on Minis . But, not what you do ChrisJ!

icesailor

PVC Primer:

Not only do some "plumbers" not use primer, they don't chamfer the edge of the pipe so the sharp edge doesn't wipe out the cement while going in to the socket.

Some use purple cleaner. Some use purple cement. Some don't use cleaner at all but use purple cement. If you can't see the writing on the side of the pipe, disappear before it goes into the socket, it wasn't cleaned.

KC_Jones

Off topic but...

Ice you are hitting another nail on the head.  I have been through manufacturers training from Spears on proper PVC pipe joint assembly.  Some things I learned the "cleaner" doesn't just clean it is actually the solvent for the pipe and is part of the "welding" of the joint together.  In addition how many "plumbers" actually hold the joint together for the appropriate time?  On smaller pipe (less than 2") it's 2-5 minutes that the pipe needs to be held in position.  On larger pipe (2 1/2"-8") it's supposed to be held together for 30 minutes.  On DWV it probably isn't a big deal because of the lack of pressure, but on any pressurized pipe it can be.  The company I work for put us all through this training a while ago and it was a huge eye opener for all.  We discovered this was the cause of some leaking pipe on our units.  I have personally watched a joint back out 10 minutes after assembly due to pipe size and cure times.  Those sockets are tapered and will push the pipe back out.  We work in PVC as big as 16" that pipe needs to be clamped up and left for at least 2 hours to cure.  All these "recommendations" are of course just that.  The bottom line though if the manufacturers instructions aren't followed the warranty is void on the pipe and fitting.

icesailor

Paying Attention:

You paid attention in class.

When the windshield wipers on your vehicle won't "wipe" the rain away, why? Because the sharp rubber edge is rounded off by wear. I used a 12" 64 tooth carbide saw blade on my chop saw. A cut was so sharp that you could cut your finger on the cut-off. What happens when you don't chamfer the edge? It wipes the cement out like a new windshield wiper blade. Like the sharp edge scrapes the cement and softened PVC on the fitting.

How many plumber's carry a PVC De-Burring tool in their bucket or bag? 4 Way files work well too. You get a rounded rasp and **** file on one side, and a flat rasp and **** file on the other.

TonyS

I always use nitrogen

Not using it would be the equivalent of tig welding without argon. What I have done to reduce my cost and time is I keep two 330cf tanks in the shop and fill a 20cf tank.

I can only equalize the pressure but I get many fills before taking the 330 in for a refill.

unclejohn

AS far as I know

Which ain't much on mini splits. You never braze it's all flare fittings. Also I've used nitro only once on a large refrig. piping job, well most of it anyway. Had the biggest bottle I could handle and still it would not last the day on big pipe.

Techman

Nitro

That video was great!! Made its point!!! Nitro is needed!!!! Did that 35 years ago !!! How many times have you made a coupling ,that beautiful bright glowing red, that intense heat kinda way?. Can you FEEL it ? That's HOT!!! I was taught that the copper goes thru some kind of "change of composition" thing when "overheated" , and overheated makes "more" oxidation/flacking. than not glowing fittings.



The "idea" of what is being done is demonstrated  superbly !!!!!!!!!!!!!!

Harvey Ramer

Copper (II) Oxide = CuO

Interesting stuff, CuO

It has been beat into my head that it is an abrasive and nitro should always be used. "Which I do, unless I'm in one of those unique situations that the books conveniently ignore." In fact, apparently CuO is used to polish optical equipment; cool.



Then there is this paragraph that I barely understand. It makes some interesting points about CuO enhancing fluid viscosity and thermal transfer.

1.1. Characteristics of CuO NPs

CuO is the simplest member in the family of Cu compounds and exhibits a range of potential physical properties, such as high temperature superconductivity, electron correlation effects, and spin dynamics [15,16]. As a semiconducting compound with a monoclinic structure, CuO has attracted particular attentions in the field. It possesses useful photovoltaic and photoconductive properties because CuO crystal structures have a narrow band gap [17]. Besides the property, CuO NPs hold novel characteristics. CuO NPs can also improve fluid viscosity and enhance thermal conductivity, and these novel properties make them a potentially useful energy-saving material that can improve the effect of energy conversion [18]. CuO NPs have been applied in different areas, including gas sensors [19], catalysis [20], batteries [21], high temperature superconductors [22], solar energy conversion [23], and field emission emitters [22]. For industrial catalysis, CuO NPs may be able to replace noble metal catalysts for carbon monoxide oxidation [24], which would reduce production cost and improve the catalytic efficiency. The suspension has excellent thermal conductivity and can be used as a heat transfer fluid in machine tools [25]. CuO is much cheaper than silver oxide and can be mixed with polymers more easily to obtain composites with unique chemical and physical properties. Because they can reduce friction [26], and mend worn surfaces, CuO NPs are used as an additive in lubricants, polymers/plastics, and metallic coatings [27]. Moreover, the extremely high surface areas and unusual crystal morphologies endow CuO NPs with antimicrobial activity, and they dose-dependently inhibit



Here is the whole article http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAA&url=http%3A%2F%2Fwww.mdpi.com%2F1996-1944%2F5%2F12%2F2850%2Fpdf&ei=muXaU_TyJY6lyASb_oLYBg&usg=AFQjCNHsfETPS9nTYUK-fduYRHsSZNcUHA&sig2=KDklJ6vFhfRVMX49kp4lgg&bvm=bv.72197243,d.aWw



Harvey

 

  

KC_Jones

Enjoying reading this

Some of the conversations on this site are thoroughly enjoying.  I am enjoying the back and forth on this topic.  I have only brazed a handful of times in my life, most of my experience is welding so this has been very educational for me.  I am just a homeowner, but I do a lot of my own work so I always like hearing and learning about how things should be done.  I am not going to try brazing refrigeration lines anytime soon that is what I learned here.

ChrisJ

Amature

Like I said, I'm only an amateur and do this as a hobby, but in my eyes if I'm willing to spend time and money to do it right, shouldn't a professional?



I will admit, my wife was anything but happy when I started dumping money into the equipment to do this but it takes what it takes.

bob_46

Juice

Chris , what kind of "juice" are you going to put in that GE monitor dome?

ChrisJ

Methyl formate

Hi Bob,



I used methyl formate as it is the original refrigerant used in the 1933-34 CA type monitor tops.

Techman

Nitro.

ChrisJ ,do you have a P/T chart for methyl  formate?

ChrisJ

P/T chart

Hi Techman,



Yes, I have two of them, one showing a curve compared to other refrigerants and this one. I'm attaching this one because I have it handy.

earl burnermann

Only once

did I see a tech use nitrogen. Everyone at the company said he was too slow. But when he gave his notice they asked him to stay for the two weeks he offered. Everyone else that resigned was out the door immediately.

On my job, If I'm there, we use nitrogen for brazing. The guy with me usually doesn't want to go the extra step, but we do.

earl burnermann

double post

 sorry

radmix

Brazing

All connections on Mini splits should be flared not brazed. the 1/4" line is so small the you could end up with a bead of brazing rod or solder in the line. 

ChrisJ

1/4"

I think a lot of the tubing I was brazing is 1/4" along with the tiny capillary tube.  If you're good you have nothing to worry about.



But as you said, the connections are all flared anyway so no need to braze.  I do wonder how good a flare connection is vs brazed though?  I'm guessing it should be fine as long as it's tightened correctly?

Ironman

Brazing on Mini Splits

Not all manufacturers require flares on their mini splits. Did a training class on ECR minis a few weeks ago and they said brazing was okay as long as nitrogen was used.



Did an LG 8 zone that someone else had started and all the separation wyes were brazed as that is what LG supplied with the units.



Regarding flaring on mini splits: the thicker forged flare nuts that are supplied with the unit should be used. They are the only ones approved for 410a. Also, a flare torque wrench should be used in tightening. I double flare everything and have not had a leak on anything in 15+ years of doing it.

radmix

Double Flair

Does a double flair mean that you flair the same pipe twice

KC_Jones

Sort of

Basically a double flare makes the flare have double the tube wall thickness.  Here is a video showing how to do it.  This one is for brake lines, but it's the same for anything.  These types of flares reinforce the end for extremely high pressures (brakes systems can see thousands of PSI).



http://www.youtube.com/watch?v=4fmF9mm3hsM

TonyS

When installing ductless ac

in second floor bedrooms on interior walls I will usually cut off the flare nuts on the indoor unit, swage, and braze longer stubs that will protrude above the attic floor. I usually do this in the shop with nitrogen then I braze one end shut and braze a schrader on the other and test. I refuse to bury a flare joint that I cant access.

radmix

Good Video

Ive been using a flair tool made for R-410 A refrigerant. I can see in the video how the thickness of the pipe increases.

Ironman

Double Flare

The tube is essentially hemmed over and the inner portion acts somewhat like a metal gasket allowing a small cushioning effect.

TonyS

Who makes your flare block?

I have one for smaller brake lines but I have not seen one for larger lines?

Ironman

Flare tool

Mine is Imperial Eastman, but the double flare dies didn't come with that tool - they were optional. I got them from Harbor Freight with a $10.00 Chinese tool. I threw the tool away and kept the dies since they were what I wanted. They are identical to those that come with the good flare tools.

TonyS

I also just found

Rigid makes one also. Im going to have to give that a shot. I have a small one I do brake lines with but have never tried it with copper.

Thanks