Welder extension

dragoneggs · Jan 17, 2017

swines said:
If you want to go by the NEC, you have to understand the difference between designing a branch circuit (panel to outlet) and an extension cord.

What you really need to take into account is the maximum current draw in Amps, and the welder's duty cycle.

As an example, if you have a welder that draws a maximum of 40A with a duty cycle of 50%, you would use the multiplication factor of .71 (from NEC Table 630.11). The calculated current draw, taking into account the duty cycle, is: 40A x .71 = 28.40A. From Table 310.15(B)(16) - a 10 gage conductor has an ampacity of 35 Amps at 75F.

Therefore, for the imaginary welder drawing 40A with a 50% duty cycle - a 10 gage extension cable would be adequate.

Isn't there a factor for length of extension cord? Is .71 factor based on a given length?

LD1 · Jan 18, 2017

Sodo said:
$.88 per foot for 10/2 SJOOW appx $62.

10/2 Romex is about $.70 /foot. That's $49

I expected the SJOOW to cost a lot more than Romex.

Yep aczlan beat me to it.

Romex 10/2 w/ground is actually 3 wires. Black, white, and bare.

10/2 so-cord is not gonna have a ground.

Need 10-3 which adds to the price. Also adding to the price is if you drop the J (junior) from the so-cord.

SJOOW is about 1.5x the cost of Romex, SOOW is about 2x

pat32rf · Jan 28, 2017

Are you looking for a production set up or just a way to use your welder when you need to repair or fabricate something? A short run of 10/3 cabtire combined with 50' of 10/2 roamex can get a lot done, especially when the roamex is only used when the shorter cord will not reach, (like out beyond the garage).
30 amp cap and bodies are normally under $10 last time I looked.

yomax4 · Jan 28, 2017

I use 6/3 for 50' extension cords. Hooked 2 together many times at shows. This is just the rubber coated black,white and green.

Tractor Seabee · Jan 29, 2017

Mark @ Everlast said:
Is that a Lincoln tombstone? It's only 125A DC.

Mark, my welder was an old Wards 225A AC/DC output. There was no Duty Cycle indicated that I paid attention too. DC is around 200A output. i know it handles 5/32 6010 rod at max setting with no problem, never had it trip out on the heat sensor even doing a 6' joint non-stop except to change rods.

Ron

Turbys_1700 · Jan 29, 2017

yomax4 said:
I use 6/3 for 50' extension cords. Hooked 2 together many times at shows. This is just the rubber coated black,white and green.

When my dad sold his motor coach 7 years ago I inherited his garage. I went to my electrician and told him I wanted an extension from the back of the garage to the front. This building was 48' that kept my dad's motor coach. I told him I wanted to run a welder and an air compressor. He installed a 6/3. Never had any issues at all running the air compressor or my welders. I think back then the cost was around $150. Can't get by for that now.

DaveK OR · Feb 15, 2017

First, check your supply voltage at various times of the day and see what you REALLY have at the plug. You may think you have 220V, but odds are it's something else.

Next, check with the welder manufacturer to see what the voltage tolerances are for "normal" operation. Typically, it's a 5% drop from the nominal voltage. If your supply voltage is higher than nominal, you have a lot of room to work with. For example, if you have a nominal voltage requirement of 220V for the welder, you can drop to 209 Volts at the welder and still be within spec. If your voltage supplied at the plug is 235 that gives you even more room to work with.

Next, go to one of the online voltage drop calculators, and using the maximum current draw of your welder (from the plug, NOT what you are using from the welder), and see what you will get for voltage drop for a given supply voltage, load, wire size, and length of wire. With that information, you will know just how long an extension cord you can get away with. Make sure your house/shop wiring is using good code-sized wiring to your outlet, and it isn't too long of a supply run, or you'll have to figure that part out as well.

I have a 210 Amp mig welder that draws around 25 Amps from the line when it's running wide open. I can run a 100-ft extension cord with #10 wire and be well within spec for the welder, even at "full throttle."

Cheapest way to build a welder extension cord is to buy a #10 wire 120V cord, cut off the plugs, and then rewire the ends to the appropriate NEMA plugs. For shorter cords, you can get away with #12 wire extension cords and still have acceptable voltage. If you really want to be careful, you can put a voltmeter on the connection at the welder and monitor how much it drops when you put it under load. If you never use the maximum amperage, you have even more margin to work with.

dragoneggs · Feb 15, 2017

DaveK OR said:
First, check your supply voltage at various times of the day and see what you REALLY have at the plug. You may think you have 220V, but odds are it's something else.

Next, check with the welder manufacturer to see what the voltage tolerances are for "normal" operation. Typically, it's a 5% drop from the nominal voltage. If your supply voltage is higher than nominal, you have a lot of room to work with. For example, if you have a nominal voltage requirement of 220V for the welder, you can drop to 209 Volts at the welder and still be within spec. If your voltage supplied at the plug is 235 that gives you even more room to work with.

Next, go to one of the online voltage drop calculators, and using the maximum current draw of your welder (from the plug, NOT what you are using from the welder), and see what you will get for voltage drop for a given supply voltage, load, wire size, and length of wire. With that information, you will know just how long an extension cord you can get away with. Make sure your house/shop wiring is using good code-sized wiring to your outlet, and it isn't too long of a supply run, or you'll have to figure that part out as well.

I have a 210 Amp mig welder that draws around 25 Amps from the line when it's running wide open. I can run a 100-ft extension cord with #10 wire and be well within spec for the welder, even at "full throttle."

Cheapest way to build a welder extension cord is to buy a #10 wire 120V cord, cut off the plugs, and then rewire the ends to the appropriate NEMA plugs. For shorter cords, you can get away with #12 wire extension cords and still have acceptable voltage. If you really want to be careful, you can put a voltmeter on the connection at the welder and monitor how much it drops when you put it under load. If you never use the maximum amperage, you have even more margin to work with.

Long ago (30 years or so) I bought a 100ft heavy duty extension cord from Costco (I was shocked to see it was 10gauge) to run my 220v air compressor. Did the same, cut off the 110v plug and socket and outfitted with appropriate 220v. Been one of the handiest things. Made a conversion plug and I can run off a dryer plug. I can now also power my MIG 211 or 45XP plasma remotely with an DIY adaptor at that end.