AC Refrigerant lines: Braze or Solder?

Discussion in 'HVAC Heating & Cooling' started by Lakee911, Nov 3, 2009.

  1. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Columbus, OH
    When my furnace/AC fails in my rental house (and it will one of these days), I'm contemplating replacing the unit myself.

    I've always seen the AC lines brazed. Why aren't they soldered? Can they be?

  2. Bill Arden

    Bill Arden Computer Programmer

    MN, USA
    The reason they are not soldered with lead solder is that the lead solder causes problems in the system.

    You can still use low temp brazing solders and a map torch, however you can't use plumbing solder.
  3. jimbo

    jimbo Plumber

    San Diego
    "plumbing solder" hasn't had lead in it for many years. But soft soldering, whether you use lead bearing solder or not, is probably not rated for the pressure of an HVAC system
  4. rzyzzy

    rzyzzy New Member

    phoenix az
    You might want to just hire the brazing done. You're supposed to flow a small amount of nitrogen through the lineset while brazing to prevent the pipes from getting black residue inside them - the residue could ruin your compressor. You can cook the valves if you aren't fast with the torch, and if you're too fast, you'll get a leak.

    Around here, I've gotten quotes of $200-ish for an hvac guy to braze the lines with nitrogen, vacuum them out (to remove moisture), and check the refrigerant levels. Still a huge savings over letting them do the complete install. Many hvac guys won't want to help you with your install, but you only need one to break ranks....
    Last edited: Nov 6, 2009
  5. rickst29

    rickst29 New Member

    There *is* a solder which works great....

    but you will not find it in an orange or blue/white "big box" store. The problems with plumbing solder are: #1, the joints are too weak; and #2, it can't handle the stresses and vibration which A/C lines experience.

    Stay-Brite-8, however, does a fantastic job, and it also begins to flow at an extremely low temperature. (That's handy when working with heat-sensitive components like TXV's). It costs a lot, though. Here's the mfgr page:

    It's best matched up with their "BRIDGIT" Water Soluble Flux, because that product also begins cleaning up the metal at just a little bit above room temperature. Be careful to avoid burning the flux-- that black gunk isn't good for compressors, either. They make a 95/5 formula too, but I'd pay the extra bucks to use the stronger 92/8 product. If you won't be using a lot of it, people sell partial-spool chunks on **** for much less than the cost of a full Spool from your HVAC supply house.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    #3 is that the residual flux will contaminate the compressor oil. NO ONE here purges with Nitrogen, unless it is for a medical gas installation.
  7. jimbo

    jimbo Plumber

    San Diego
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