Multiple welder outlets - #6 pigtail splice type and box size?

[buening]

I'm in the planning stages of my garage build and am planning on having a welder outlet at the back wall and in the front wall. The welder is a Lincoln Powermig 255, and the manual states I could technically get away with #8 wire if it is in conduit and 75° copper, however #6 romex is quite a bit cheaper and easier to run. In looking at the 50A outlets, it doesn't appear I could get away with not needing a pigtail or splice (like a regular 15a wall outlet). As best as I can tell, I will need a connector for 3-#6 wires since a pigtail would be needed. Split bolt connectors appear to only be for 2 wires, and from what I've read is old tech and a pain to use. The polaris connectors look to be pretty optimal, but are quite large and concerned about fitment inside a box (or making sure there is room). Any other connection ideas?

I'm also trying to determine what box size I'll need for the first box containing the pigtail, can someone verify my calcs? My box fill calcs (assuming plastic box) are 6-#6 conductors + 1-#10 ground + outlet = 6x5 + 1x2.5 + 2x5 = 42.5 cu in.

It appears 22.5 cu in is a big as I can get with a single gang PVC box, and a 4" square deep box has 35.0 cu in. Would I have to go with a 2-gang box with a single gang mud adapter plate? From what I can tell the polaris connectors aren't included in box fill calcs but they physically take up room, so I would think they would need to be accounted for especially since there would be three of them.

Also, I'd like to use a single gang outlet cover if possible, which would likely require a mud ring due to the larger box. Is this allowed or does the junction box have to be fully accessible per code?

 

[justsam]

I will let a real electrician answer your specific questions, and offer an alternative.

Since you are in the planning and pre-build stage, I would consider putting these outlets on separate breakers, each a dedicated circuit. I have two such outlets in my garage, and one typically has my TIG welder plugged in and the other has a portable 240VAC heater occasionally plugged in. Admittedly, I have not had the occasion to be running both at the same time, but if I were to do so, and had pedal down on TIG, it would be an issue.

Only you can determine if now, or in the future there might be two high amperage consumers on your proposed single circuit at one time.

 

[pattenp]

If your garage is residential use then multiple outlets aren't allowed on a single circuit larger than 20A. This is a 2012 IRC requirement E3702.5.

 

[sublimate]

Mine is a residential garage and multiple 50a 240v outlets were allowed. I did 2 circuits, each with 3 outlets.
They did the splices in separate boxes, not in the outlet boxes.
I can take some pics later this week if you'd like.

 

[theoldwizard1]

Mine is a residential garage and multiple 50a 240v outlets were allowed. I did 2 circuits, each with 3 outlets.
They did the splices in separate boxes, not in the outlet boxes.
I can take some pics later this week if you'd like.

When was the work done ? Was it inspected ?

 

[pattenp]

I should have said if your locallity adops/enforces the 2012 IRC then multiple outlets over 20A aren't allowed on a single circuit.

 

[wyliesdiesels]

If youre gonna be putting multiple CCC(current carrying conductors) in conduit make sure to do the derate calcs to make sure the wire doesnt need to be upsized.

 

[buening]

I'm thinking the separate breakers may be the best solution. The local inspector said to just follow the NEC. Thanks for the IRC section reference, that helps me confirm the requirements.

The subpanel will be on a side wall closest to the outlets, so it may even save wire if I run them on separate circuits. Plus it eliminates the headache of splicing this large of wire and messing with the huge junction box. I will have plenty of breaker slots, so that won't be an issue. Thanks for the tips everyone!

 

[alfredeneuman]

I'm also trying to determine what box size I'll need for the first box containing the pigtail, can someone verify my calcs? My box fill calcs (assuming plastic box) are 6-#6 conductors + 1-#10 ground + outlet = 6x5 + 1x2.5 + 2x5 = 42.5 cu in.

You don't need to include the pigtail wires when doing box fill calcs

It would be only 4-#6 conductors, thus reducing the volume required to 32.5 cu in.

 

[sublimate]

When was the work done ? Was it inspected ?

Work done this year.
Yes, it was inspected.
My city has adopted the 2012 ICC.
My understanding is it was approved because it was for welders, not "general purpose" outlets.

 

[MoonRise]

#6 THHN, run it to the receptacle/outlet.

Use a two gang box and put the appropriate coverplate on it for the big diameter NEMA 6-50R outlet.

Done.

+1 on run two different circuits. This way you can run a welder and an air compressor, or a plasma and an air compressor, or a whatever and a whatever.

And if you do decide to run a wire smaller than the #6 copper on a 50 amp breaker for a welder, using the welder duty-cycle exemption, note that you are supposed to label that receptacle as "For Welder Use Only!" (or similar).

 

[pattenp]

Work done this year.
Yes, it was inspected.
My city has adopted the 2012 ICC.
My understanding is it was approved because it was for welders, not "general purpose" outlets.

This is where the inspector makes the difference. Once you have a circuit that supplies more than one outlet it is considered a general purpose circuit. It doesn't matter what's being plugged into it.

 

[alfredeneuman]

And if you do decide to run a wire smaller than the #6 copper on a 50 amp breaker for a welder, using the welder duty-cycle exemption, note that you are supposed to label that receptacle as "For Welder Use Only!" (or similar).

It may be a good idea, but there is no requirement to do so.

 

[sberry]

It is so much easier to run 2 circuits if there are spaces. Its one of the reasons its a great idea to have a larger panel, way less tempting to hook up something less than stock lets say.