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The other day I had my air conditioning repaired, and one thing I saw the technician do is braze the copper pipes together. This got me thinking why don't I see that done in electrical setting.

I understand that soldering is not good because it is brittle and a short circuit can melt those connection out of their joints. But brazing temps are so high that if it does melt something else more important have already melted before it. I mean I don't think there are generic splicing kits (8 AWG or thinner) can handle brazing temps.

Taking it a step further, how about TIG welding? It basically melts the copper into a liquid state to join them for sure this makes a good connection, unpractical it may be. Just cover the welded part with heat shrink and voila ! a proper connection

Are there any electrical code (in your countries) that prohibits copper wire welding or brazing? I would see medium sizes wires can benefit from this (6-10 AWG maybe). Is it banned just because installers and technician cant do it properly consistently enough to be reliable?

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  • \$\begingroup\$ It's a lot easier to use a junction box for cable installation. Plus it risks melting the insulation to soler and definitely to braze. \$\endgroup\$
    – Finbarr
    Commented Apr 9 at 13:40
  • \$\begingroup\$ @Finbarr but the connection is good? like it was never cut. melting insulation is not a problem for example on bare grounding wires. \$\endgroup\$
    – DrakeJest
    Commented Apr 9 at 14:19
  • \$\begingroup\$ Are you sure what you saw was brazing? Copper tubes are commonly soldered with the same types of solder that are used for wires, although they generally use more aggressive fluxes. The soldering might be done using an acetylene torch just because the pipe itself acts as an effective heatsink, but it's still a tin or tin-lead solder with a melting point of 200±25 °C. \$\endgroup\$
    – Hearth
    Commented Apr 9 at 19:25

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The Canadian electrical code 2018 has no such “ban”, merely a reasonable caveat on soldering.

12-112 Conductor joints and splices 1) Conductors shall be spliced or joined with splicing devices or by brazing, welding, or soldering with a fusible metal or alloy. 2) Soldered splices shall first be spliced or joined so as to be mechanically and electrically secure without solder and then be soldered. 3) Joints or splices shall be covered with an insulation equivalent to that on the conductors being joined. 4) Joints or splices in conductors and cables shall be accessible.

Whether there are further restrictions in specific cases or if it’s practical to make field connections in the suggested manner is left for your further research. I would think TIG or brazing would be fine in practice for bus bars, for example.

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  • \$\begingroup\$ Number 2 is weird, so you include the mechanical connector in the solder? or mechanically secure it with some connector then solder presumably close to the mechanical connector? \$\endgroup\$
    – DrakeJest
    Commented Apr 9 at 16:39
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    \$\begingroup\$ @DrakeJest No. Number 2 means that you must make a solid mechanical joint (generally by twisting wires together) before soldering, so that the solder does not need to provide the mechanical strength for the joint. It is generally good practice. \$\endgroup\$
    – Math Keeps Me Busy
    Commented Apr 9 at 19:25
  • \$\begingroup\$ What s/he said. In the olden days it was widely considered bad practice to use solder for any mechanical connections, including component leads, so they would be cinched or twisted to a terminal block etc. before soldering. Now that we have microscopic components for SMT it's no longer so frowned upon. \$\endgroup\$
    – Spehro Pefhany
    Commented Apr 9 at 23:06

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