240V 50A Receptacle for Welder

[cybikorpg]

I'm installing a dedicated circuit for my welder. The welder needs a standard 6-50R receptacle.

I read a topic from 7 years ago with similar circumstances. There seem to be two answers, so I'm looking for guidance on what is best.

The welder draws fewer than 30 amps. Strictly a nice-to-have if a bigger welder could be accommodated in the future.

I ran #10 in a conduit, and there will only be the one receptacle for a welder. The duty cycle of the welder is something like 60% at 200 amps.

Do I use a 50 amp or 30 amp breaker?

 

[mike93lx]

If the 50 is available and not wildly expensive, I would use the 50. It would. Be annoying to have it trip in the middle of a project.

Running the 30 won't do any harm

 

[theoldwizard1]

If the 50 is available and not wildly expensive, I would use the 50. It would. Be annoying to have it trip in the middle of a project.

Running the 30 won't do any harm

It could !

10 AWG is only rated for 30A !!

 

[mike93lx]

It could !

10 AWG is only rated for 30A !!

Good lord. Stop talking about what you clearly don't understand.

10 is more than enough for this.

 

[rancherbill]

It could !

10 AWG is only rated for 30A !!

You were looking at stranded wire, solid core is 52 amp.

 

[mike93lx]

You were looking at stranded wire, solid core is 52 amp.

No. Standed vs solid is not an issue at all

Welder circuits are a different animal.

 

[laser3kw]

My research and advice from GJ was : Plan for the future (owner), as long as you are starting from scratch, go all the way.
So I went 50 amp breaker, 50 amp receptacle and 6 gauge wire. If I were to have a 30 amp machine, I could put a 30 amp breaker if I want to with no harm.
The breaker should match wire capacity. 10 ga generally will have a 30 amp breaker. YRMV

 

[KenC]

No. Standed vs solid is not an issue at all

Welder circuits are a different animal.

The welder calculations really look weird though when you're used to dealing with the normal rules. I have 3 welder locations in my shop. One installed by the original builder way back in 66 or 67 and two by me later. Mine was installed by the rules and both combined cost way less than the one original. Because he used the 'normal' calcs.

 

[Norcal]

Welders are subject to different rules, but if in conduit I would use 8 AWG THHN with a 50A breaker, if wired as a welder outlet it should have signage stating that.

 

[alfredeneuman]

You were looking at stranded wire, solid core is 52 amp.

The ampacities of solid and stranded are exactly the same
52 amps =

 

[mike93lx]

My research and advice from GJ was : Plan for the future (owner), as long as you are starting from scratch, go all the way.
So I went 50 amp breaker, 50 amp receptacle and 6 gauge wire. If I were to have a 30 amp machine, I could put a 30 amp breaker if I want to with no harm.
The breaker should match wire capacity. 10 ga generally will have a 30 amp breaker. YRMV

Personally, what the next guy does is his problem, not mine. But we can all spend our money how we want to. Not understanding the way things work doesn't feel like a great reason to make decisions

 

[wyliesdiesels]

It could !

10 AWG is only rated for 30A !!

you clearly dont know how to size wire for welder circuits. sit back and learn something from the pros

 

[wyliesdiesels]

You were looking at stranded wire, solid core is 52 amp.

huh?

what code in the NEC permits different ampacities for stranded & solid wire? go ahead I'll wait.

Hint: you wont find such a code...

 

[nadogail]

The rules for welders take into account that a welder is not a continuous load.
For example the power cord on my AC/DC transformer welder is only 12 Gauge.
I chose to use 8 gauge wire to connect it to a 60 Amp breaker.

 

[cannuck]

I will start of by saying I am just the mechanical guy who works with a bunch of electrical people, but some of that stuff rubs off on me from time to time. I have yet to see an ampacity table for 10 ga. that hits 50A - and from what I have seen there are a LOT of considerations as to how much wire you need to be LEGALLY able to connect to a 50A rated receptacle. The temp insulation rating of the wire, the wire material and how many conductors are inside of a conduit all come into play. One thing for sure: (well, in my limited understanding) if you have a 50A recept you need to have wiring capable of carrying the load or have a smaller breaker to prevent it being used at that load. Must defer to your local sparkies about code compliance of putting that receptacle in without matching wire, but probably gets by with correct breaker.

Now, as to special rules for welders? I have some 100% duty cycle machines, and if used in production they would likely see very close to that actual use. What do "the rules" say about something like that? I tend to run wires for worst case scenario, not best case or whatever I can get away with. Yes, costs more, but once you have had your shop burn down because some freshly injected and tested breaker didn't prevent a device that had some kind of internal short (obviously with resistance) to ground light up the plywood structure it was mounted on you will take some of these things a lot more seriously (and conservatively).

 

[mike93lx]

I will start of by saying I am just the mechanical guy who works with a bunch of electrical people, but some of that stuff rubs off on me from time to time. I have yet to see an ampacity table for 10 ga. that hits 50A - and from what I have seen there are a LOT of considerations as to how much wire you need to be LEGALLY able to connect to a 50A rated receptacle. The temp insulation rating of the wire, the wire material and how many conductors are inside of a conduit all come into play. One thing for sure: (well, in my limited understanding) if you have a 50A recept you need to have wiring capable of carrying the load or have a smaller breaker to prevent it being used at that load. Must defer to your local sparkies about code compliance of putting that receptacle in without matching wire, but probably gets by with correct breaker.

You have this wrong. Welders are an exception.

50a breaker and receptacle with #12 is fine for many welders.

I chose to run 10 for mine as it was short and I had to buy the wire anyway.

 

[cannuck]

You have this wrong. Welders are an exception.

50a breaker and receptacle with #12 is fine for many welders.

I chose to run 10 for mine as it was short and I had to buy the wire anyway.

Could be, just that I have never seen such a table. Usually 30-40 Amps for most classes of 10ga I have seen.

 

[mike93lx]

Could be, just that I have never seen such a table. Usually 30-40 Amps for most classes of 10ga I have seen.

Lots of posts in this forum about it. Has to do with duty cycle. Regular ampacity tables don't apply.

That said it's your money. If running #6 for your welder makes you feel better, send it

 

[wyliesdiesels]

Could be, just that I have never seen such a table. Usually 30-40 Amps for most classes of 10ga I have seen.

here ya go

https://www.ecmweb.com/national-electrical-code/qa/article/20889547/code-qa

 

[cannuck]

here ya go

Thanks to yourself and mike93lx I am now familiar with section 42 of the Canadian NEC. Didn't know it existed. It has correction factors based on the three different kinds of welders as well as duty cycle. Up here, you can even have a breaker GREATER ampacity than the nameplate x correction factor of the welder to accommodate inrush currents. Thanks for the information and inspiration.

 

[mike93lx]

Thanks to yourself and mike93lx I am now familiar with section 42 of the Canadian NEC. Didn't know it existed. It has correction factors based on the three different kinds of welders as well as duty cycle. Up here, you can even have a breaker GREATER ampacity than the nameplate x correction factor of the welder to accommodate inrush currents. Thanks for the information and inspiration.

Your name should have give it away, but I didn't relative you were a canuckistani. Rules up there are different and what I was talking about is US-specific. Glad you were able to find more applicable info

 

[mcbane]

I ran #6 to all of my welder outlets because I wanted the flexibility to connect my larger welder at any location. That still requires swapping out the receptacle for a fixed connection and putting in a separate breaker for that location, but at least I dont need to pull new conductors.

 

[TRWham]

I will never understand the posters here who treat the ampacity tables in Article 310 of the NEC as if they were handed down by God to Moses etched into stone tablets, but then turn around and assume the various committees who write other portions of the code, like 430, 440, 630 and the tap rules in 240 are idiots.

 

[EricS]

Thanks to yourself and mike93lx I am now familiar with section 42 of the Canadian NEC. Didn't know it existed. It has correction factors based on the three different kinds of welders as well as duty cycle. Up here, you can even have a breaker GREATER ampacity than the nameplate x correction factor of the welder to accommodate inrush currents. Thanks for the information and inspiration.

Glad you found SEC42 in CEC

Table 1-4 cover ampacities and are the ones people go to but take a look at Tables 12, 12A and 12E. Those are also ampacity tables that get missed. In particular when people are using Sjoow and Soow( aka CABTIRE cable). Once you start using above #12AWG Sj/So the ampacity drops off compared to using Table 2 which people use when ordering Sj/So cable

I use Table12A alot and you'll notice those cables have more ampacity than what's offered by equivelent gauges in Tables 1-4