Brazing the last joint with Nitrogen purge

[600SL]

Hopefully tomorrow I will be brazing in my new heat pump.

My question is can I purge by passing Nitrogen from the condenser high side through the expansion valve and back through the low side line or the reverse. Another words will the expansion valve be open and allow this to happen. If not what should I do when I get to the last fitting. I can regulate with either flow or pressure. What are the recommended flow or pressure ranges. Also first time using an acetylene torch in many years what should I set the pressure to.

Any other tips would also be appreciated.

I will be using a Harris air acetylene torch with Stay-Silv 15 0.050 x 1/8" no flux. Line set is 3/8" and 1 1/8". Torch tips will be #11 and #3

 

[Brian_WK]

Hopefully tomorrow I will be brazing in my new heat pump.

My question is can I purge by passing Nitrogen from the condenser high side through the expansion valve and back through the low side line or the reverse. Another words will the expansion valve be open and allow this to happen. the valve will be open so this I find just set the pressure very low on the nitrogen and allow plenty of pre purgeIf not what should I do when I get to the last fitting. Put the last fitting dry fitted then pull the Schrader cir of the low side test pressure ports.I can regulate with either flow or pressure. What are the recommended flow or pressure ranges. High enough to allow flow but low enough that you don't cause back pressure that can cause blow out at your joints. I recommend flow of you have it.Also first time using an acetylene torch in many years what should I set the pressure to.I used OXY acetelene 99.9% of the time but everyone one that I know that used air acetylene always ran it wide open

Any other tips would also be appreciated.

I will be using a Harris air acetylene torch with Stay-Silv 15 0.050 x 1/8" no flux. Line set is 3/8" and 1 1/8". Torch tips will be #11 and #3

Their will be some discussion about this but it has worked very well for me for well over 5k weld joints ranging from residential to grocery stores. Start your heat on the bottom of the pipe but not aiming the flame into the joint. Heat all around the pipe until you are back on the bottom this takes about 15-20 seconds on 1-1/8 pipe than direct your heat on the coupling starting at 3 or 9 o'clock which ever is on the back side from you. Start heating and quickly keep testing with your weld stick until it starts talking the filler and flows into the joint keeping your heat on the coupling. Work your way to 6 o'clock filler following flame until you are at your close side of the fitting. Then continue on around the joint until you reach your starting point with a slight overlap of where you started. If it is a coupling you can immediately start on the next joint no need to pre heat the pipe on the other side of the coupling.

Cherry red is too hot. Move your torch away to control heat.

Wrap your service valves, filter drier, and expansion valve with wet rages and pull Schrader cores to prevent melting them.

Clean both the inside of fittings and the pipe with brushes and cloths etc.

If you are having trouble reaching a back side of a pipe a 90 degree bend of your filler can make it more accessible. Don't grab the filler towards the end right after brazing it's damn hot. Use a pliers to bend it.

Good luck!

Brian

 

[600SL]

Their will be some discussion about this but it has worked very well for me for well over 5k weld joints ranging from residential to grocery stores. Start your heat on the bottom of the pipe but not aiming the flame into the joint. Heat all around the pipe until you are back on the bottom this takes about 15-20 seconds on 1-1/8 pipe than direct your heat on the coupling starting at 3 or 9 o'clock which ever is on the back side from you. Start heating and quickly keep testing with your weld stick until it starts talking the filler and flows into the joint keeping your heat on the coupling. Work your way to 6 o'clock filler following flame until you are at your close side of the fitting. Then continue on around the joint until you reach your starting point with a slight overlap of where you started. If it is a coupling you can immediately start on the next joint no need to pre heat the pipe on the other side of the coupling.

Cherry red is too hot. Move your torch away to control heat.

Wrap your service valves, filter drier, and expansion valve with wet rages and pull Schrader cores to prevent melting them.

Clean both the inside of fittings and the pipe with brushes and cloths etc.

If you are having trouble reaching a back side of a pipe a 90 degree bend of your filler can make it more accessible. Don't grab the filler towards the end right after brazing it's damn hot. Use a pliers to bend it.

Good luck!

Brian

Thanks

Will be doing some practice first. Hopefully have this done today. Will report back.

 

[600SL]

Well I tried a few practice brazing today. I didn't like the results. I tried both air acetylene and oxy acetylene. Air came out better. I had more control but both did not get penetration more than 1/2 way down. With the oxy I started to melt the fitting. Oxy acetylene braze is on the left air acetylene is on the right. Both were done with no purge but the oxy acetylene is much cleaner.

I know practice make perfect but this is a $5500 Heat pump install so I'm going to wait until I have a guy that can braze this and commission the system.

Thanks for the help.

 

[dreasoner]

What pressures are you running on the oyx acetylene? Brian uses the same approach I use. it is a matter of practice to get the proper feel. I typically use about 7 psi on the acetylene and 10 - 12 psi on the oxygen. Everybody will tell you something different. I do 2 passes on the joint. first pass pulls in the braze rod and second pass adds a small fillet to the joint. That is what I was taught for ultra low refrigeration work where leaks are very costly.

 

[R.Anderson]

Well I tried a few practice brazing today. I didn't like the results. I tried both air acetylene and oxy acetylene. Air came out better. I had more control but both did not get penetration more than 1/2 way down. With the oxy I started to melt the fitting. Oxy acetylene braze is on the left air acetylene is on the right. Both were done with no purge but the oxy acetylene is much cleaner.

I know practice make perfect but this is a $5500 Heat pump install so I'm going to wait until I have a guy that can braze this and commission the system.

Thanks for the help.

No need for oxy acetylene, just a acetylene torch will do. Both look too hot, and you need to purge. The reason systems are purged is the same reason why you failed to fill the gaps between the fittings. Copper reacts and oxidizes when exposed to oxygen in the air when it is that hot.

Melting the copper is way too hot, you just want to melt the filler rod to braze not to create a fusion weld. With that purge, purge, purge.

Give a practice go again while purging with nitrogen and use just a acetylene torch, bet your results will be what you want.

 

[R.Anderson]

Well I tried a few practice brazing today. I didn't like the results. I tried both air acetylene and oxy acetylene. Air came out better. I had more control but both did not get penetration more than 1/2 way down. With the oxy I started to melt the fitting. Oxy acetylene braze is on the left air acetylene is on the right. Both were done with no purge but the oxy acetylene is much cleaner.

I know practice make perfect but this is a $5500 Heat pump install so I'm going to wait until I have a guy that can braze this and commission the system.

Thanks for the help.

No need for oxy acetylene, just a acetylene torch will do. Both look too hot, and you need to purge. The reason systems are purged is the same reason why you failed to fill the gaps between the fittings. Copper reacts and oxidizes when exposed to oxygen in the air when it is that hot.

Melting the copper is way too hot, you just want to melt the filler rod to braze not to create a fusion weld.

Give a practice go again while purging with nitrogen and use just a acetylene torch, bet your results will be what you want.

 

[R.Anderson]

Another thing is the fit of the fittings, if the gap is too big it will not fill properly.

 

[600SL]

What pressures are you running on the oyx acetylene? Brian uses the same approach I use. it is a matter of practice to get the proper feel. I typically use about 7 psi on the acetylene and 10 - 12 psi on the oxygen. Everybody will tell you something different. I do 2 passes on the joint. first pass pulls in the braze rod and second pass adds a small fillet to the joint. That is what I was taught for ultra low refrigeration work where leaks are very costly.

I had the oxy acetylene adjusted to 5 acetylene and 10 oxygen.

For the air acetylene i set it to 5.

Looks to me like I wasn't hot enough at the back end to **** the material in. I was kind of trying to do what you describe.

 

[600SL]

No need for oxy acetylene, just a acetylene torch will do. Both look too hot, and you need to purge. The reason systems are purged is the same reason why you failed to fill the gaps between the fittings. Copper reacts and oxidizes when exposed to oxygen in the air when it is that hot.

Melting the copper is way too hot, you just want to melt the filler rod to braze not to create a fusion weld. With that purge, purge, purge.

Give a practice go again while purging with nitrogen and use just a acetylene torch, bet your results will be what you want.

I thought the purge wouldn't effect the braze only the inside soot that's why I didn't purge for practice. Definitely more comfortable with the air acetylene.

I normally don't give up so easy but these practice runs were on a bench. The real brazing with be done 15' high on a step ladder.

Right now I have the AC lines installed and ready to braze so prefer to get someone with demonstrated experience finish this part of the job off before I make an expensive mistake.

 

[600SL]

Another thing is the fit of the fittings, if the gap is too big it will not fill properly.

They were both swagged pipe that fit nicely but I believe the oxy acetylene deformed that one and made it looser. probably from the weigh of the rest of the pipe trying to fall out of it.

 

[bazar01]

I normally don't give up so easy but these practice runs were on a bench. The real brazing with be done 15' high on a step ladder.

Why do you have a joint 15' high ?

You should have ran a continuous line set so you only braze on the ground and on the indoor unit location.

 

[600SL]

Why do you have a joint 15' high ?

You should have ran a continuous line set so you only braze on the ground and on the indoor unit location.

The air handler is 15 ft high. There is also 1 elbow 15' high.

 

[bazar01]

The air handler is 15 ft high. There is also 1 elbow 15' high.

Got it.
So this is an open ceiling in a garage and the air handler is suspended.
I would plan on putting a wooden working platform on the bottom chord of the truss for servicing the unit.

 

[600SL]

Got it.
So this is an open ceiling in a garage and the air handler is suspended.
I would plan on putting a wooden working platform on the bottom chord of the truss for servicing the unit.

There is no bottom chord. But I am considering a set of scaffolds for service.

 

[welder4956]

I will be using a Harris air acetylene torch with Stay-Silv 15 0.050 x 1/8" no flux. Line set is 3/8" and 1 1/8". Torch tips will be #11 and #3

3 psi Acetylene / 3 psi oxygen for a #3 Harris brazing tip.

You need a tip chart to get the proper settings. Here is an example, but may not be for your torch:

http://www.harrisproductsgroup.com/~/media/Files/PDF/Tip%20Flow%20Charts/1390_23A90_5090_8490_Acetylene_Flow.pdf

http://www.harrisproductsgroup.com/en/Technical-Documents.aspx

 

[600SL]

3 psi Acetylene / 3 psi oxygen for a #3 Harris brazing tip.

You need a tip chart to get the proper settings. Here is an example, but may not be for your torch:

http://www.harrisproductsgroup.com/~/media/Files/PDF/Tip%20Flow%20Charts/1390_23A90_5090_8490_Acetylene_Flow.pdf

http://www.harrisproductsgroup.com/en/Technical-Documents.aspx

Thanks for the chart.

I did get this done successfully today and I now I have a working system. The guy who did it brought his own oxy-acetylene torches. Everything worked fine but when he got to the low side manifold he was having difficulty. He tried my Harris oxy-acetylene torches with a number 3 tip set pressures to 5 and 10 psi and all was well. I think this would have been real difficult with an air acetylene torch and a wet rag in place.

 

[600SL]

So now that this is up and running I will consume the rest of my acetylene practicing on some scrap tubes. It worked out good but it was not the job for me to be getting up to speed with.

Many thanks for all the replies.

 

[OccupantRJ]

I have many years using coiled silver solder to braze many shapes and types of tubings and different metals together with great results. I have never understood why service guys use the flat stick form of the solder. I get less than desirable results every time I try to use it on anything I have ever tried it on.

On an ac repair once years ago, a guy gave me some of the flat rod to try, which I did with little satisfaction. I regrouped and went to the round coil type and it flowed slick as snot. I can silver braze 3/4" copper tubing with a handheld butane torch using it. So my basic question is, why do service and maintenance guys other than me use the flat type solder?

 

[600SL]

I have many years using coiled silver solder to braze many shapes and types of tubings and different metals together with great results. I have never understood why service guys use the flat stick form of the solder. I get less than desirable results every time I try to use it on anything I have ever tried it on.

On an ac repair once years ago, a guy gave me some of the flat rod to try, which I did with little satisfaction. I regrouped and went to the round coil type and it flowed slick as snot. I can silver braze 3/4" copper tubing with a handheld butane torch using it. So my basic question is, why do service and maintenance guys other than me use the flat type solder?

I did read the pros and cons and certainly have used silver solder (round coil stuff) for older R-22 systems without any problems. The flat type solder is not really solder its brazing allow. Much higher melting point ~1400° vs ~500°. Think of solder more like gluing. Brazing like alloying.

With the new 410 system pressures and temp run hotter and do push the margins of the solder, but you are correct it should and usually works fine.

 

[samss]

45% silvaloy is about three times the cost of 15%. The filler material depends on what metals you are brazing together. Copper to copper, either one works fine. Any other metals, 45 or 55% and flux.

 

[Brian_WK]

Yep price. Install a grocery store or a large piping job. The price difference will be in the 1000's.

Other than that it is personal preference. I love the 15 stick and run it almost like I'm Tig welding. The 45 coil (they also have a stick version) flows more like solder and melts at a lower melting point as stated, also requires flux which I hate.

Brian

 

[LS6 Tommy]

IMO, oxy acetylene for 3/8" & 1-1/8" is WAAAY overkill. A tubotorch is more than enough. 410a systems MUST be brazed or silver soldered. Nitrogen purge is always the best way to go. I opt to braze with Sil-Fos and purge....

Tommy

 

[600SL]

IMO, oxy acetylene for 3/8" & 1-1/8" is WAAAY overkill. A tubotorch is more than enough. 410a systems MUST be brazed or silver soldered. Nitrogen purge is always the best way to go. I opt to braze with Sil-Fos and purge....

Tommy

The guy that did mine was having a lot of difficulty with his oxy acetylene at the 7/8" service manifold. His torch appeared to be working well but it would not do the job. I had to loan him mine and that worked OK. I believe by looking at his gauges on his gas bottles that they were in poor condition and may have been off a little. But I kind of doubt that the acetylene only would have done the job in this area without difficulty. Remember in this area you are fighting against the wet rag.