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  • Why?

    Why do the copper lines on HVAC system's need to be brazed instead of soldered?

    I asked a fairly old HVAC guy and he had no idea. I was like wtf?!

    I even talked it over with my old timer boss and he didn't know.

    We thought about pressure, but solder can hold it's own.

    Is it that freon acts old on solder joint's I'm assuming?

    Thanks for teaching me some Hvac.
    Proud To Be Union!!

  • #2
    Re: Why?

    Aaron. We braze refridgeration lines because solder will not hold up to the extreme pressures and expansion and contraction of the joint. Also the soldering process introduces acids to the system that are harmfull to the compressor and react with the refrigerant. There are some guys out there that are using specialty solders and fluxes though I do not like or trust them. (the solder, not the guys) Silver soldering is also sometimes used near delicate valves where too much heat could damage them. Silver solder is of course flux less.
    Hope that answers your question.
    sigpic

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    • #3
      Re: Why?

      AC system is subject to more vibration and higher pressure, typically around 280 working pressure. This will cause premature failure of a solder joint. There is something called "silver soldering" which expensive but it does works and is basically soldering. Pic of soldered refrigerant lines when they blew.
      Attached Files
      Buy cheap, buy twice.

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      • #4
        Re: Why?

        NH and Ben- Thanks you answered my thirst for knowledge. Nice picture Ben.
        Proud To Be Union!!

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        • #5
          Re: Why?

          Its been years since I have seen the soft solder for reefer equipment. I dont even remember the name of the solder or the flux they sold with it. I have seen several soft solder joints fail in residential a/c applications. I think it would work fine for low-temp stuff. (low-temp=low-pressure)

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          • #6
            Re: Why?

            Alot of guys used to soft solder the low pressure side of ref systems in order to save money and time. Running pressure usually doesn't exceed 80 psi, but during off cycle it increases to well over 100 or 150 on the low side. I never have always silver solder. I have heard that a joint that is silver soldered is actually stronger than the pipe alone. Kind of like a weld. Some say that a weld is stronger than the metal welded.

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            • #7
              Re: Why?

              Originally posted by MPMGinAL View Post
              Alot of guys used to soft solder the low pressure side of ref systems in order to save money and time. Running pressure usually doesn't exceed 80 psi, but during off cycle it increases to well over 100 or 150 on the low side. I never have always silver solder. I have heard that a joint that is silver soldered is actually stronger than the pipe alone. Kind of like a weld. Some say that a weld is stronger than the metal welded.
              Sounds like a lot of hackery going on in Alabama when it comes to HVAC.
              Buy cheap, buy twice.

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              • #8
                Re: Why?

                In the past, a lot of guys used Sta-brite silver solder to join refrigeration lines. The pressures of the old R-22 systems were lower than the newer "environmental friendly" units. In my last house had the lines joined with Sta-brite and 12 years later, the system has no leaks and performs flawlessly.

                Last year, I moved to a different house (10 year old R-22 system) and in September, the A/C performance began to degrade. I traced the problem to a leaking evaporator due to improper installation. The drain pan was sloped away from the outlet and the capillary tubes rotted at the junctions to the A-coil because the junctions were under water most of the time...

                I bought a new evaporator and liquid line filter, and asked for a roll of Sta-brite and the buy behind the counter said not to use it. I asked him what to use and he said Sta-silv 15. That stuff is EXPENSIVE ($3.00 per stick) and I had to use my oxy-acetylene torch to braze the joint. I was nervous about learning the new technique on a $250.00 evaporator so I practiced on some copper plumbing fittings. Everything worked out with the evaporator install - it's just the silver brazing technique was much different than silver soldering.

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                • #9
                  Re: Why?

                  As an A/C contractor, with 18 years of experience, I'll throw in my two cents worth. I have been using Harris Stay-Brite 8 for many years and have yet to experience a problem. I previously used Silfoss until seeing a J.W. Harris Company display at a trade show. The demo had a copper pipe brazed with Silfoss and another copper pipe soldered with Stay-Brite 8. Both pipes were put under hydraulic pressure until the joint split, where the fitting was brazed where Silfoss was used. The Sta-Brite joint expanded but did not split. That demo convinced me that presssure was not a problem with the soldered joint.
                  However when using solder, use only Stay-Brite 8 as it has silver added to give it great strength and resistance to vibration. Also clean the joint and fittings WELL and use acid flux sparingly. The advantage of using solder is lower heat 430 deg. versus 1200-1500 degrees using brazing. The low heat will not form oxidation inside the pipe as will the high temperatures required for brazing. Try both methods and see which you like and make your own decision. The end of my epistle.

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