HVAC piping

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Hello all just a question,  I ran into the A/C installer on the job and was surprised to see him brazing the copper piping.  I always thought they just used plumbers solder,  has anyone been involved with this type work or could tell me what type of brazing rod that is required or have any comments.  Thank you  Clifton
Reply:Sil-Phos. It's 5-10% silver with some phosphorus for self fluxing on copper only. Not to be used on steel do to the phosphorus and doesn't work well on brass either without flux. Been the standard in the industry since before I was born. For A/C installation you need to keep it clean and using flux with soft copper won't do. Plus you need more strength in the joint for the high pressures involved. Thought I have run into some large pieces that where soft soldered on the low pressure side. Probably as much do to the heat needed to get a large piece of copper up to brazing temps as anything.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:thanks just wasn't what I expected   thanks clifton
Reply:The newer freon substitutes develop some horrendous pressures. They are moving up to like 15% silver now."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Sil-phos is also used for medical gas piping using copper. The fitters clean all the fittings then braze them together. All piping is sealed and stored with caps. Worked doing electrical in a lot of hospital environments.RegardsDave
Reply:Originally Posted by smilindaveSil-phos is also used for medical gas piping using copper. The fitters clean all the fittings then braze them together. All piping is sealed and stored with caps. Worked doing electrical in a lot of hospital environments.RegardsDave
Reply:Originally Posted by BD1Yes, plus all piping AC and medical gases require a Nitrogen purge . Most all med gas fittings are purchased cleaned and bagged by manufacture.
Reply:In other countries they just use flare fittings. In the US the code doesn't allow that.The new R410A systems run around 400 PSI max, typically more like 180PSI.The proper/typical way to do HVAC piping is to purge/flow nitrogen while brazing with OA using Sil Phos sticks. Pressurize with nitrogen, pull deep vacuum for as long as possible to check for leaks. Or do triple evacuation, using shallow vacuum and purge with nitrogen 3 times.Plenty of hack jobs are happening where guys are using ordinary plumbing solder and techniques and everything works fine. Most of the guys who use sil phos and OA don't purge with nitrogen. Some of the guys don't even pull a vacuum before charging.A lot of guys put filter driers on, they help to trap some of the crud and keep it out of the compressor. That way you can do a really crappy job and still have the equipment last just long enough so that the customer doesn't sue you.
Reply:''The new R410A systems run around 400 PSI max, typically more like 180PSI.''I don't know where you are located , but on a 95 degree day 410A  normal suction pressure is around 118 PSI and normally discharge is 400 PSI. Some discharge pressures can hit 600 PSI. Our normal test pressure is 600 PSI on a system that operates at 400.A old R22 has a suction pressure of 68 PSI and a discharge of 250 PSI on a 95 degree day.
Reply:In other countries they just use flare fittings. In the US the code doesn't allow that.The new R410A systems run around 400 PSI max, typically more like 180PSI.The proper/typical way to do HVAC piping is to purge/flow nitrogen while brazing with OA using Sil Phos sticks. Pressurize with nitrogen, pull deep vacuum for as long as possible to check for leaks. Or do triple evacuation, using shallow vacuum and purge with nitrogen 3 times.This is correct except for the flare fitting comment. All ductless split systems use flare fittings and many compressor accessories are also flare fittings.I have been doing HVAC for years and know of no code or regulation from any agency or jurisdiction that will not allow flare fittings. I suspect it was cost decision from manufactures.The new refrigerants are blends and also extremely hygroscopic so guys are doing better work of the piping. If you lose some of the charge you have to remove the old charge completely evacuate the system to 500 microns and recharge the system. That get pricey.Triple evac is the standard with the third time is to 500 microns and in cryogenic system its down to 100 microns (micron is a millionth of an inch so its a very deep vacuum. This is done for a couple of reasons one is air is a non condensable and the boiling point of water is lower to really dehydrate the system)  In cryogenic systems you will also see true silver solder used to solder copper to stainless in some applications such as Swageloks. That stuff is sold by the Troy once and is about $50-60 an once plus flux.
Reply:First, i'm not an HVAC guy. These are just some observations of work I have seen done by HVAC guys. The pressure measurements are off my split system at home. Maybe their are higher pressure systems. Either way 600 PSI isn't really that high pressure.The manufacturers don't certify their systems to use flare fittings. My understanding is that is because the EPA won't allow it. I'm not sure why they allow that on mini split. Either way, you install a central split system with flare fittings here in California it will not pass inspection. They sometimes even want the mini splits brazed. The install manual for my central AC even says all pipes must be brazed using such-and-such.
Reply:Mud I appreciate your comments, I was an HVAC contractor in LA CA for 20 years and the I never heard of a EPA nor SCAQMD ruling on the flare fitting. Though I can tell you most guys don't know how to make a good flare and that is very expensive as far as warranty work. Sliver soldering is usually cheaper and faster than flares.
Reply:thanks everyone for the input.  I was just interested why the installer was using O/A instead of MAPP.  The info about the fittings explains the whole brazing processes,  since plumbers on site used solder and MAPP.  Thanks again for your answers  Clifton
Reply:Originally Posted by gmakraMud I appreciate your comments, I was an HVAC contractor in LA CA for 20 years and the I never heard of a EPA nor SCAQMD ruling on the flare fitting. Though I can tell you most guys don't know how to make a good flare and that is very expensive as far as warranty work. Sliver soldering is usually cheaper and faster than flares.
Reply:''First, i'm not an HVAC guy. These are just some observations of work I have seen done by HVAC guys. The pressure measurements are off my split system at home. Maybe their are higher pressure systems. Either way 600 PSI isn't really that high pressure.''600 pounds isn't that high pressure  !!!!   IF you had a 410A system fitting blow in your house at the evaporator coil or outside at the condenser you would think you were hit by a bomb . We had a manufacture start up on roof top HVAC equipment with 410A  per job specs. Unit was running at around 400 PSI , normal operating pressure, when a fitting blew on the discharge line. The fkn roof shook, the guys dam near $hit their pants, and the school maintenance men called 911.  600 pounds is high pressure. Granted it is not operating at 2,000 PSI like a steam generator but 600 PSI is dam high to me.
Reply:Well it depends where you draw the line. Keep in mind 1/2" schedule 40 PVC is rated for up to 400 PSI, minimum burst pressure around 2000 PSI.Most cheap plastic air hose is rated 300 PSI.I would not describe any of these as "strong", 600PSI is still pretty low pressure and well within the capability of a soft solder joint. Maybe it's medium pressure, but it certainly isn't high pressure. Look at your gauge hoses, probably rated for something like 1000PSI working, 3000 burst, they aren't particularly strong.Regardless, 600 PSI is well within the capability of any kind of properly made soft solder joint on a small sized pipe.Whether or not it sounds like a "bomb going off" has more to do with how much air is moving vs the pressure. A foot away from the leak, the pressure will only be slightly above atmospheric. I have a ball valve on my air compressor to dump the tank, you could blow your ear drums even at low pressure if you open the valve too fast, even if the tank only has 30 PSI in it, it just moves a large volume of air.
Reply:One thing that has not been discussed is contamination from flux used in soft solder. Water based or NoKorode will not play well with all the new refrigerants.And the comment on using teflon tape on flare fittings because they leak thats just sloppy work with a unusual solution to stop the leak. Same people will tell you to use pipe dope on your tire beads when you have new tires put on.