Multiple welder receptacle wiring

[rattle_snake]

I am planning on installing four 6-50R receptacles for my welders, plasma cutter and future 230V machinery. Most welding equipment I have looked at has a 6-50 plug, regardless of it's input current requirements (for example, my Miller 375 PC needs only 14A) so I want to use the Nema 6-50. I am not interested in sharing a single 50A extension cord for all my machines. The four receptacles would be on one wall, all within 20' of one another.

I am past final inspection, but my goal is to remain code complaint. At this time I have a single run of 6/3 NM to a single receptacle, feed from the shop's sub panel.
I understand welder circuits are a special case and can use smaller wire if labeled as such, but runs are short so I want to use #6 to match the 50A receptacles.

The county I live in uses IRC 2012 and NEC 2011;
IRC E3702.5 Branch circuits serving multiple loads or outlets.
General-purpose branch circuits shall supply lighting outlets, appliances, equipment or receptacle outlets, and combinations of such. Multi-outlet branch circuits serving lighting or receptacles shall be limited to a maximum branch-circuit rating of 20 amperes.

So I believe my best option is to install a sub panel on the existing 6/3 run, and use a 50A breaker and #6 wire run to each of the four receptacle. The panel and breakers aren't that expensive.
Thoughts?

 

[slackdaddy1]

I ran into the same thing,
I needed 3 of the typ welders 50amp outlets for my Mig, plasma and future tig.
I as it is a garage that may have a wet floor for some od reason, I really wanted even the welder outlets on a GFI breaker.
Each of these pieces of equipment draw less than 20amp at 220v.
And I would never be running more than one at a time.
I ran 10-2 wire with a 30amp breaker and have 3 outlets in a row.
I had to use DEEP 4" boxes to make my connections and fit the NEMA 50amp outlet in each box.
As far as I am concerned, as long as my breaker matches the wire size, it is good.

 

[rattle_snake]

...I ran 10-2 wire with a 30amp breaker and have 3 outlets in a row....As far as I am concerned, as long as my breaker matches the wire size, it is good.

I agree this method is safe and adequate for intended use. I started down this path but I don't care for the idea of a 50A receptacle on a 30A circuit. I am also looking for something code compliant.

The only other code complaint method I know would be to add 3 additional 50A branch circuits from the shop sub panel each with a single dedicated receptacle. Given the distances this method would cost at least 2x that of the sub panel method. The benefit would be allowing multiple machines to run at the same time, however my current service to the shop wouldn't allow it anyhow and I don't have any clones of myself. yet.

 

[ishiboo]

I agree this method is safe and adequate for intended use. I started down this path but I don't care for the idea of a 50A receptacle on a 30A circuit. I am also looking for something code compliant.

What about having a larger-than-necessary receptacle bothers you?

 

[rattle_snake]

What about having a larger-than-necessary receptacle bothers you?

The mismatch and my twisted mind. I believe the point of the NEMA system is to be able to know what voltage and amperage conductors and breakers feed a receptacle.

I am more concerned with code compliance. Multiple 30A capable receptacles disguised as 50A's still violates IRC E3702.5.

 

[wyliesdiesels]

Since u are under the IRC/IBC, then multiple 240v outlets >20a is no go as you have already discovered.

So cheapest option is a sub like u have already figured out. And thats what i would do...

Sounds like you figured out your issue on your own...

 

[aircommuter]

Planning is everything.

 

[sberry]

You could hook 4 number 12 to the breaker and be safe from a technical standpoint. They could be spliced to the 6 as a combination of them couldn't overload the wire before the breaker tripped on thermal. This is how an electric range is wired. We did this in a Buds garage that was short of spaces, simply spliced to smaller cables to the old big cable and add 2 outlets. This was for 2 new small welders, even can use the old buzzer if needed.
This is not to say you should do this but is a short explanation of circuit design that could allow it.

 

[sberry]

With the small machines and short duty cycles one could operate about 6 or 7 of them on one circuit with management.

 

[sberry]

50 will run 2 of these and in case of some machines 3 at the same time. I am not familiar with residential in this case but it's in a garage. A panel won't hurt, sometimes it's the easiest and very simple, makes the connections easy, could use 10 cable for branches and put any factory cord machine on except 250 feeders. It would even support those with conventional process.

 

[rattle_snake]

Since u are under the IRC/IBC, then multiple 240v outlets >20a is no go as you have already discovered.
So cheapest option is a sub like u have already figured out. And thats what i would do...
Sounds like you figured out your issue on your own...

I cheated and used the elusive search utility on this site to take credit for someone else's knowledge. Shhh, don't tell anyone.

Planning is everything.

Yes... 29 conduits, that looks interesting. More info?
I try to be patient and utilize GJ's collective brainpower before cutting long expensive pieces of wire into short ones.

Sberry, thanks for the info.

 

[sberry]

The minimum wire size for this class of welder is 14. When you do that it requires a max breaker of 30,,, using the 50 outlet. With a single outlet it could use a 12 wire and a 50A breaker. You could splice 2 number 12 to an 8 or 6 wire then to a 50 or each 12 to the 50 provided it had provisions for multiple wire, point being that a combination can't be allowed to overheat the wire before the splice. Range/oven combos were wired like this, 12 from each spliced to big wire then to breaker. Smaller ones were 14's to a 10 and to 30.

 

[sberry]

There is good reason to keep this away from residential. One being the nature of most equipment being on demand, water heater, electric dryer etc, they use the full capacity of the circuit and also depend on the circuit breaker for internal fault protection in much of the machine.
There isn't headroom between that and breaker size for multiple machines that may be so with welders or even some shop tools. While the welder draws only 20A it is designed to be able to be connected to a common 50A welder circuit, it won't overload it, 2 units won't overload it.