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Question for Sparkys - Is field welding of copper conductors allowed under the NEC?

Joe Gwinn

Stainless
Joined
Nov 22, 2009
Location
Boston, MA area
I was watching an interesting youtube video of building one's own house (somewhere in the vast Russian plains of Asia), and was struck by the part on wiring the house. No wirenuts or crimps. They just stripped and twisted together a bunch of solid copper wires, used a heavy copper-jawed ground clamp next to the insulation, and touched the ends of the copper wire bundle with a carbon-rod that connects to the ground clamp through a medium-size 12-volt car battery. I assume that the carbon rod is the negative. The arc quickly melts the wires into a common ball of copper. No flux used. When it all cools, a heavy plastic tube is heat-shrunk down onto the joint.

It's in Russian (which I don't know), but the pictures are clear enough. This (ELECTRICIAN in the house without rules, do it yourself? HOW TO BUILD A CHEAP HOUSE? #15) is from the My Galaxy youtube channel. The companion (mostly in English) channel is Creative Galaxy. The welding is around 13 minutes into the following:

⚫Как легко сделать ЭЛЕКТРИКУ в ДОМЕ Своими руками? КАК построить ДЕШЕВЫЙ Дом? ►15 - YouTube

And the following (ELECTRICAL WIRING without Rules. Do it yourself. HOW TO BUILD A CHEAP HOUSE? # 17), where we see that it uses a welding transformer of some kind, not a battery, at 11:37:00 in:

⚫ЭЛЕКТРОПРОВОДКА Своими Руками | КАК построить ДЕШЕВЫЙ Дом? ►17 - YouTube

Now, in the US I think that soft (tin-lead) soldering is still an acceptable (albeit rare) way to join copper wires, but I never heard of welding, or brazing for that matter. So, I'm curious.

They do seem to be making connections that are buried in the walls, and not in an accessible box, which I assume is forbidden in the US (even if OK in Russia), even if one welds all the connections.

My question is what chapter and verse in the NEC would all this come under, and what does it say?
 
First time I saw copper conductors welded was in an anodising plant where I worked, the welder tig welded the bus bar using helium shield, I had a go, copper can get away really quick, the puddle is fluid, like water fluid, tricky to get a weld and to be honest maybe copper tig welding was a bit advanced as I’d never used a tig torch in my life!, I’ve seen copper being welded for the power track of gantry cranes also so it is a thing however I’ve never seen it on copper conductors, but I suppose it would work, I’d be concerned that there may be some HAZ causing a problem?, brittle fracture or somthing nasty, I’ve welded copper many times since 1979, but not electrical, we used to weld? The copper tips on 5 hole oxy lances ( these are 14” diameter water cooled beasts 30 m long it’s a copper to steel joint, go figure but it works so perhaps it’s more braze than weld, the copper rods wet, so there might be silver, ended up we got the copper tip friction welded to a steel pipe and stovepipe welded the steel to steel, much better set up, no cracks, and you didn’t blow the top off the Lance dumping copper in the steel, and copper mixes through steel faster than any element, so quickly you use copper as a tracer to find out if steel making units like vacuum degassing are working properly mixing the steel for homogeneous slabs.
Seen contacts welded, they weren’t coming apart anymore.
Just rambling but trust the Russians to do somthing differently ( one of their MIGs was gas welded together according to a guy I spoke to from Dynamo Gorsk
Mark
 
Don't know about the NEC, however years ago I was involved with a massive ground loop system that was connected with joining fixtures and
some form of weldment. Cadweld comes to mind. This was meant for large diameter conductors; I don't think you'd want to do this around
flammable materials.
 
From the standpoint of joint electrical and mechanical integrity, welding is certainly acceptable. The problem is practicality. As mentioned, welding pure copper is and art and is not for the johnny-come-lately. Welding copper or aluminum conductors is nothing new, done all the time in building large electrical machines such as transformers.

Tom
 
From the standpoint of joint electrical and mechanical integrity, welding is certainly acceptable. The problem is practicality. As mentioned, welding pure copper is and art and is not for the johnny-come-lately. Welding copper or aluminum conductors is nothing new, done all the time in building large electrical machines such as transformers.

From the videos, it did not seem all that difficult to fusion weld what looked like three AWG #14 or maybe #12 conductors together at the tip.

When I revisited the second video above, English subtitles came up, and they explained their thinking.
 
From the videos, it did not seem all that difficult to fusion weld what looked like three AWG #14 or maybe #12 conductors together at the tip.

When I revisited the second video above, English subtitles came up, and they explained their thinking.

On a lot of vids you can get a translation if you do closed caption, helps but is not perfect most times. Click the icons at the bottom, sorry, I cant remember the exact one right now...
 
I've tigged together worn out Weller soldering gun tips, adding extra at the end for shaping/cleaning. Just used ordinary solid copper wire for filler. I think I used AC on that.
 
I've tigged together worn out Weller soldering gun tips, adding extra at the end for shaping/cleaning. Just used ordinary solid copper wire for filler. I think I used AC on that.

Hmm. The transformer box shown in the video looked to be all iron and copper, and no silicon, so most likely it's doing AC welding. Voltage doesn't seem that high. Could be the transformer out of an an old spot welder. (Added: Would need to replace the original one-turn secondary.)

AC cleans the surface oxide, which will help when welding copper in air, without flux.

The person doing the wire welding wore no protective gear, and didn't seem the worse for it, so it cannot be all that powerful. (I think I'd use OA welding goggles at least.)
 
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ive worked at a factory when i was younger, we built plating units that had massive transformers that we built from scratch and wound etc. and yes we added all the leads to the copper strip windings by welding them and welding on lug terminal strips to bolt to. so im sure it is fine as long as it is engineered properly.

also sent 3000A through 4" wide by 1/2" thick copper for about 30 seconds and it got about 800C or better and turned black, I can still remember the CEO/Boss in the shop that came out after he turned it all the way up to test a temperature probe in the transformers that kept going negative -40C every time the transformer got turned up on it from all the noise interference traveling through the thermo-couple
 
A friend who knows the NEC well answered the question.

Yes, welding is permitted, as is brazing and soft-soldering. But they cannot be buried in a wall.

I have personally used soldering, when in High School (circa 1965) I had to attach a big copper ring terminal to a very thick cable (stranded AWG #0 (1/0)?), to power a 220-Volt (3 phase, 100-amp ?) stage lighting control board, and did not have the big hydraulic crimper that would be needed. This terminal would be bolted to a big copper buss bar. So, I soldered it with plumber's grease flux, 50-50 solder, and a propane torch. Worked without difficulty.


NEC section 110.14 Electrical Connections.

(B) Splices. Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be spliced or joined so as to be mechanically and electrically secure without solder and then be soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an insulating device identified for the purpose.

Wire connectors or splicing means installed on conductors for direct burial shall be listed for such use.


Section 300.15 Boxes, Conduit Bodies, or Fittings —Where Required.

A box shall be installed at each outlet and switch point for concealed knob-and-tube wiring. Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed. Where the wiring method is conduit, tubing, Type AC cable,Type MC cable, Type MI cable, nonmetallic-sheathed cable, or other cables, a box or conduit body shall be installed at each conductor splice point, outlet point, switch point, junction point, termination point, or pull point, unless otherwise permitted in 300.15(A) through (L).

The common exceptions are splices within panels and “luminaires” (essentially fluorescent lamp boxes), and certain splices in direct buried conductors.
 
NEC says (or said, my copy is 2008) that certain earth grounding conductor connections must be welded. This is usually done with a standard, prepackaged thermite kit.
 
The welding method described in post 1 is similar to how thermocouples are welded in the field.

USA code would never allow any form of splice without a visible junction box but rural Russia is probably a place where the major code is "get it done".
 
Exothermic (thermite) welding is commonplace where irreversible connections are required - particularly in certain grounding and bonding applications. Mind you this is an engineered process that has been tested and evaluated, not some 'genius' playing electrician with a buzz-box and a lamp carbon.

Also worth mentioning that the code is a minimum standard - it does not really speak a whole lot to the reliability or 'correctness' of particular splicing practices being employed. That's on you. If you try to perform an unshielded carbon-arc weld of hospital essential branch conductors using a car battery because it's 'code', and that weld later fails in the middle of someone's surgery because it sucks - guess who's going to have a horde of bloodthirsty lawyers chasing after them?
 
just some notes from personal experience in all the mentioned joining techniques;

1) "soft solder" as we know it is a really, really shitty conductor, and should ONLYbe used, as per code, to provide a mechanical/chemical means of retaining, protecting and securing an otherwise sound copper to copper connection. there is a reason plugs and connectors have the instructions "DO NOT TIN CONDUCTORS".

2)welding electrolytic copper, the kind found in copper wire, results in outgassing of dissolved O2, which is abundant therein. the resulting weld will tend to be brittle as a result, regardless of the method used. this weld will be susceptible to fatigue cracking if subjected to cyclic loading or deflection. some transformer joints are prone to vibrate at 60 Hz, and so are usually restrained in the insulation layers or windings.

3) clean copper to copper contact, retained, compressed and protected by external pressure, such as the common wire nut, proper crimp, screw terminal, or even the "bug" splice or tap, are proven to be reliable, and if done with care are the current standard means.

4) yes, such connections however preformed, should absolutely be in an accessible location.

5) connections preformed under factory conditions, in a listed device, are entirely a different thing than field connections.

cheers, and happy electron piping!
 
OFHC copper TIG welds beautifully, ETP not so much. It is very thermally conductive, so it can be a challenge to keep it from turning into a puddle on the table, especially if it is a small piece. Subsequent annealing in a reducing atmosphere, hydrogen good, carbon monoxide better, further improves conductivity.
 
The welding method described in post 1 is similar to how thermocouples are welded in the field.

Yes. Jewelry welding too. Except that they are usually capacitor discharge. I've seen capacitor discharge TIG, with each pop delivering from 65 to 150 Joules.

USA code would never allow any form of splice without a visible junction box but rural Russia is probably a place where the major code is "get it done".

Yes, it seems. Although the fellow building the house has clearly thought about this a lot - he is not cavalier.

It turns out that the house is in the suburbs of Kiev, Ukraine, but same difference.

I figured out another detail: There is no grounding system in the house (very common in the old days), and the power company's modern solution is a whole-house ground fault interrupter. What is delivered to the house is true three-phase power (not split phase as in the US), each phase being ~220 volts to earth, with ~418 volts between phases.

The house seems to be all electric. I don't recall seeing any gas connection or oil tank.
 
I've seen silver phospor copper brazing rods used frequently in silver brazing copper conductors together for grounding systems. These were located in power substations and on cellular and radio tower sites.

Cadwelding was also used to bond copper conductors to the base of lattice towers and monopoles.
 
I've seen silver phospor copper brazing rods used frequently in silver brazing copper conductors together for grounding systems. These were located in power substations and on cellular and radio tower sites.

If this is what I think it is, it's the same as used on Freon-carrying copper tubing in air conditioners and the like. The big advantage is that no flux is needed. This is essential, because it's pretty hard to clean the spent flux unit of such an assembly.

Cadwelding was also used to bond copper conductors to the base of lattice towers and monopoles.

I had not heard of that brand. Like thermite, but for copper or aluminum.

I have seen ~thermite welding of heavy copper ground conductors to A36 steel beams, reportedly for lightning rods. May have been cadweld.
 








 
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