Help with welder circuit

[mccayry]

First off I would like to say thanks for all the helpful info that is available on this forum.
I have a 40' by 70' workshop that I am preparing an estimate for. The HO wants 2 circuits for future wiring of a welder. The total run would be no more than 100'. I was just curious what size circuit I should run that would be large enough for the specific type welder. Thanks in advance

 

[Little Bill]

First off I would like to say thanks for all the helpful info that is available on this forum.
I have a 40' by 70' workshop that I am preparing an estimate for. The HO wants 2 circuits for future wiring of a welder. The total run would be no more than 100'. I was just curious what size circuit I should run that would be large enough for the specific type welder. Thanks in advance

What specific size welder? Kind of hard to size a circuit without more info. Are there going to be 2 different welders, or do they just want to plug in one welder in different locations.

 

[mccayry]

The HO has no clue he just want to circuits so that if he ever gets a wild idea to start welding then he will be set up. My thoughts were a max 250A welder

 

[Little Bill]

The HO has no clue he just want to circuits so that if he ever gets a wild idea to start welding then he will be set up. My thoughts were a max 250A welder

IMO, the HO would probably have to choose a max size welder he would want to use, and you would have to wire it to that and calculate the VD for the length of the run. He would be limited to that size or smaller welder when he decides to buy one. You didn't say whether he wants 2 welders or 1 with the ability to plug in at different locations. If it is the latter, you wouldn't need 2 circuits because only 1 receptacle would be used at a time.

 

[mccayry]

The HO wants to be able to have 2 welders. I will have to check with him on the size of welder he will be planning on. Thanks

 

[G._S._Ohm]

From the welder specs I've seen,
when you calculate backward from the power delivered to the workpiece to the line current at 120 V or 240 V,
they actually draw more from the line than the rated CB steady state amperage
and so they depend on short welding times so that the amps squared seconds is just low enough so the breaker doesn't trip.

You might have to pick and choose the trip curves.

The welders have a duty cycle spec. and I guess the CBs also need time to cool down.

You'll be more certain of no nuisance trips
if the HO picks his welders first
or at least tells you the max. size welders [with their max duty cycles] he would ever want to upsize to.

You could tell him the wiring cost vs. size options and let him pick his welders and whether he wants both to run at the same time.

 

[zbang]

If you're running pipe, install an empty (1"?) from the panel to a j-box in the approximate location. Install wire & connections when he figures out what welder to get.

 

[mccayry]

The HO has 2 welders that he wants in his workshop. I am going to give him 2 separate circuits. I have never messed with sizing circuits for welders. I looked at one today that was using #6 with a 50amp plug protected by a 100 CB. Here is some of the info the HO gave me for the welders. The run between panel and Outlet will be about 90'. Any help would be greatly appreciated. Thanks

Welder #1

AC-GTAW-125A-100% duty-75
AC-GTAW-200A-40% duty-75
AC-30-250A-40% duty-75
DC-30-250A-40% duty-75
DC-GTAW-250A-40%-75

Welder #2

Volts- 28
Amps- 200
Duty- 60%
Max OCV- 42

 

[mengelman]

I have hooked up lots of welders. On welder #2 what you have posted is the output. All of them I have seen listed the input and the output voltage and amprage. I have only seen a couple of big industrial machines that used more than a 50 amp circuit. I have a 200A Miller MIG that is quite common in industrial shops. It runs on a 50A circuit. Hope that helps.

 

[G._S._Ohm]

Welder #2

Volts- 28
Amps- 200
Duty- 60%
Max OCV- 42

28 x 200 = 5600 W assuming the welder is a resistive load. With welder inefficiency this is slightly more than 23 A at 240 V. A 20 A CB might work with a low welding duty cycle, depending on it's trip curve.
A 25 A CB will probably work in any case.

 

[K8MHZ]

I looked at one today that was using #6 with a 50amp plug protected by a 100 CB.

That doesn't sound good....

 

[realolman]

I think you need to find out the line side voltage and current requirements of the specific welders he plans to use.

There really are different types and sizes of welders... there are some that plug into a 120 v recept. , but as one of the earlier posters said, I believe a welder that requires more than a 50 a. recpt. @ 240 v would be rare... I can't see anyone having one at their home... but who knows.

You really need to know what he plans to use ... or you could just install 240v 50 a. recepts..... then he'll show up with a 120v wire feed.

 

[stew]

The 2 units you describe are a stick welder/tig and a mig probably all in one feeder/welder. I woned an electric motor shop in seatllte for 17 years and our shop specialized in the sale and repair of all types of arc welding equipment as well. I was teethed on welders so to speak. Any how get me the brand and model and I will get the input specs for you and provide you with some wiring info. Done tons of these. The specs sound like Miller or Lincoln to me.

 

[Little Bill]

28 x 200 = 5600 W assuming the welder is a resistive load. With welder inefficiency this is slightly more than 23 A at 240 V. A 20 A CB might work with a low welding duty cycle, depending on it's trip curve.
A 25 A CB will probably work in any case.

According to Table 630.11(A), with the welder that was mentioned, it was a 60% duty cycle and at 28A that would be 22.68A and he would have to use a minimum 25A breaker. In any case the HO would need to stay within the limits of the wiring, if it is done in advance, to choose his welders.