Tying multiple wires together instead of a single large conductor..?

52 Ford · Aug 29, 2021

I accidentally cut the cord on one of my welding machines. It had a 12AWG cord and I looked around and didn't have a replacement. I did have an extra 14AWG extension cord, though. I cut it into two sections, doubled up the wires, crimped on terminals, soldered them, put 1" heat-shrink over the whole thing, installed it, and it works fine. I only made about a 4-1/2 foot cord.

Anyway, I had to open up the welding machine to bolt the wires in place, which tool quite a while. So, this cord is going to be on for a while, till I get time to take it apart again. 14 AWG is 2.1 square mm. 12 AWG is 3.3 square mm. Unless I'm missing something, the two 14 AWG conductors aught to have more ampacity than the single 12 AWG conductors - right? This is a temporary fix, mind you. I did this on the weekend and wasn't able to go to the store to buy some SJOOW.

ANYWAY - My question:

How would x2 - 14 AWG stranded copper conductors compare to the single 12 AWG stranded copper conductor I replaced?

Speaking specifically of the wire... Assume the connections on each end are fine. I did the best I thought I could. Crimped terminals on as tight as I could, then soldered them.

Sent from my SAMSUNG-SM-G891A using Tapatalk

technocrat · Aug 30, 2021

No problem. Your replacement cable 2 x 2.1 square mm = 4.2 is much larger than the 12AWG at 3.3 sqmm, so even with different purity copper you have plenty of capacity. It all comes down to how much heat is generated by the current (amps) flowing. The more resistance in the wire (or connector crimp) the hotter it will get. Lower purity and smaller cables run hotter for the same current. At some point, that exceeds the insulation temperature and the smoke gets out. Check your temperatures after welding and if cool, all is good.

52 Ford · Aug 30, 2021

technocrat said:
No problem. Your replacement cable 2 x 2.1 square mm = 4.2 is much larger than the 12AWG at 3.3 sqmm, so even with different purity copper you have plenty of capacity. It all comes down to how much heat is generated by the current (amps) flowing. The more resistance in the wire (or connector crimp) the hotter it will get. Lower purity and smaller cables run hotter for the same current. At some point, that exceeds the insulation temperature and the smoke gets out. Check your temperatures after welding and if cool, all is good.

That was my thinking. I just wan't to make sure I'm not skipping over something that should be obvious and create a hazard.

In my experience, fire can be fun - but only when you want it. Electrical fires can be really inconvenient.

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WizardOfBoz · Aug 30, 2021

One aspect that may be of interest is that most current in AC flows nearer the surface of the conductor (the skin effect). Your two smaller conductors have about 60% more surface area and therefore are even better than the 25% higher cross section you mentioned.

On certain high-frequency, high current apps, they use braided tubular wire, or even tubes or pipes, to carry current but to save the extra expense of pounds of copper.

EPAIII · Aug 30, 2021

Will it work? Well, as long as all the connections are good and tight, sure it will.

Is it code? I really do not know, but I kind of doubt it.

What happens if one of the current carrying connections is not tight and has a bit more resistance. Well, it will heat up and at some time, fail. Then the other wire carrying that current will be overloaded and it will also fail at some point. And there is probably no warning of this.

I would do it for an emergency (night/weekend) repair but would replace it as soon as the hardware or electrical supply store is open in the morning. MAKE time to take it apart again.

And DO keep any flammable substances away from it until then. Keep yourself away too.

DDoug · Aug 30, 2021

So the breaker is sized for the total amperage.
When one conductor of the pair get's damaged (complete break) the other will take all of the current, and the breaker is now 2x sized for that single conductor.

Remaining conductor will get red hot and may melt, all the while the breaker will not trip.

I have witnessed this happening.

ViktorS · Aug 30, 2021

I was taught not to do this in the electrical courses I participated in.
Why? Because electricity flows the easiest path and there is NO guarantee that the two wires take equal load. In fact there is almost a guarantee they won't.

But for a bootstrap solution to get shit through the door it will probably work.

boslab · Aug 30, 2021

Now I’m straining the brain …but here goes, Kirchhoffs law, the current coming out is the same as the current going in or vice versus as you like, how it divides itself I don’t know, equally seems instinctive but I suppose if there was a temp difference or some damage then the situation would change, I’m going to guess it’s not a preferred method in case one cable of the pair failed or broke then there’s a chance the remaining cable would the go overload, possibly catastrophic failure, fire flames etc!
Mark

donie · Aug 30, 2021

Yo termite! Yooous wires are shorting on yer fooked Parker stacked Monarch 10ee drive! That was yer legacy here!
Itz dat poo on yer shooz agains?

eKretz · Aug 30, 2021

That skin effect is generally - like Thermite mentioned - only really applicable for very high frequency AC, which 60Hz is not. The bodge will be fine until you can replace it.

donie · Aug 30, 2021

Yuh! the termites nos his chit cuz he vented betterz 10ee divz cuz hiz wires goez evea where!

Whats the problem termite! Your bull shit fail you in the Monarch forum?

DDoug · Aug 30, 2021

eKretz said:
That skin effect is generally - like Thermite mentioned - only really applicable for very high frequency AC, which 60Hz is not. The bodge will be fine until you can replace it.

Or a mouse chews thru one conductor, or a piece of steel drops on it.

Scottl · Aug 30, 2021

I agree with thermite re the insurance issue.

While electrically it is ok to use it as a temporary repair you should obtain the correct replacement welding cable ASAP.

Don't ever give an insurer any excuse to deny a claim.

mjr6550 · Aug 30, 2021

My two cents is, yes it will work, but I would replace the cord when you get a new one, because it is not correct from a code standpoint. I don't recall the exact code, but from what I recall you can only double conductors with wires somewhere around 1 gauge or larger. I may be wrong about 1 gauge, but I think it is around that gauge, if not larger.

GregSY · Aug 30, 2021

I'm not sure what kind of wimpy welder would use a #12 conductor...but I assume it was an internal transformer tap or something.

All of the above advice is good. But no one has yet touched on the real answer, which is age related.

If you are 23 year old, go back in and use a 12 gauge wire to fix it in a timely manner.

If you are 80 years old, you (hopefully) understand the true magnitude of your fix as it relates to the universe and that there is no need to ever think about it again.

GregSY · Aug 30, 2021

I will add that in the world of Big Boy power, it is very common and 'to code' to use multiple conductors on a single phase.

For example, a recent generator project used (4) 750MCM cables per each of the 3 phases. And some of the motors connected to it used (3) 500MC cables per phase.

This is work engineered by top-level industrial engineering firms and installed in top-level industrial plants.

4GSR · Aug 30, 2021

Worked on a motor-gen set project where we had to power a 150 HP DC motor that ran on 240 Volts! I don't remember the exact amperage needed. Had to order nearly 500 feet of 500 MCM THHN cable. Made up two parallel cables, two conductors each for plus and minus and ran that in 4" conduit. About 80 foot run. I'm glad I wasn't the one that pulled that cable. It worked! Later the company pulled that motor and gen set and replaced with nicer Reliance 150 HP 460 volt DC motor with power supply. Much smaller cable was used on that hookup.

donie · Aug 30, 2021

Hey termite, your death threats toward me seem to be empty, your threat of other members here ruining me financially, and or killing me have not born fruit!
So, kiss my ass Rooster Fish!
Say "fuck face" your life time wasted work in the Monarch forum has turned to shit! Looks like you are a fake electrician to boot!
termite you are a total looser........and a punk, and a....STALKER,

rons · Aug 30, 2021

I would hate to be assigned the task of coming up with the equations for mutual inductance/capacitance between the two wires.

Just a Sparky · Aug 30, 2021

Paralleling conductors smaller than 1/0 AWG is illegal.

Paralleling feeders and service conductors 1/0 AWG and larger is permitted, provided certain conditions are met. Off the top of my head including but not limited to;

- All conductors in a given phase are exactly the same length and terminated in exactly the same fashion.
- All conductors in a given phase must be run through the same wiring method.
- All conductors in a given phase must be of identical material and have identical insulation.

Additionally:

- Isolated phases must not pass through any closed metallic loops. i.e. no metallic conduit or metal strut straps & unistrut, 'Minerallac' fittings, etc. if using isophase arrangement.

Pass 400 amps AC through a lonely 600 KCMIL and wrap a piece of metal around it? You've just created a 1:1 transformer and that metal will get *real* hot in a hurry.

Demonstration of this effect:

https://youtu.be/ZEi0cnUrlwQ?t=196

Tying multiple wires together instead of a single large conductor..?

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