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#72041 - 11/17/06 04:06 AM welding receptacles... how many?  
u2slow  Offline
Joined: Sep 2003
Posts: 200
Salt Spring, BC, Canada
Would you ever put more than one 6-50R on a circuit for convenience sake?

If there was only intention of keeping one such machine, and one worker/hobbiest on the premises, it wouldn't bother me. However, there will be a plasma cutter also, and a good possibility of it being a 2-man shop at least part of the time. I'm trying to avoid overly long cords also. (60x72 building, 30x40 work area).

What would you do in this situation?

Work Gear for Electricians and the Trades

#72042 - 11/17/06 05:45 AM Re: welding receptacles... how many?  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I would (and have) put as many welder outlets where convenient for the users.

I would talk to the customer and be up front with them.

I can do it for this lower price and it may trip, or for more money I can separate them and prevent any possibility of a trip.

Also it is worth taking a look at the "Electric Welders" Article in the NEC (630 in 2002). The rules are much different than the normal rules, you may use smaller circuits than you expect depending on the welders duty cycle.

[This message has been edited by iwire (edited 11-17-2006).]

Bob Badger
Construction & Maintenance Electrician

#72043 - 11/17/06 06:53 AM Re: welding receptacles... how many?  
Trainwire  Offline
Joined: Mar 2002
Posts: 360
It would also seem to me to be an issue of what you are gluing together.

Around here we have welders with up to 500 amp capacity, and one with a 100% duty cyle at 800 amps. But how often are they turned up that far? Almost never. Only when we air/arc somthing.

So if all you are doing is light duty stuff, this might not be the issue you think it is. Welders are rated for their max output, turn em down and you would be suprised at how little they draw.


#72044 - 11/17/06 07:17 AM Re: welding receptacles... how many?  
e57  Offline
Joined: May 2003
Posts: 2,876
Well, do they have two welders now to base anything off of? If not, IMPO I wouldnt worry about the possible future use, unless it was defintate, and the use of the shop was specificaly "welding" or metal fabrication, rather than say an auto shop that did some welding perioricaly. Otherwise you would end up with something the size of a feeder that may be totaly unnessesray. Considering you are basing you assumption off of receptical rating.... If you look at the nameplate rating it may be a different story. Mine has the same 50A receptical, but has a 21A input max @ 30% duty. That said I could have two of the same unit on the same 50A circuit.... The multiplier for a 30 duty cycle is .55 for mine. That shop might not have the same welder... It is the name/data plate that you need to base your decision on.

See 630.11[b](A)]/b] + then (B), and if you look at 630.12, you'll realize the cord cap and breaker for it is already double sized most often.

630.11(B) Group of Welders. Conductor ampacity shall be based on the individual currents determined in 630.11(A) as the sum of 100 percent of the two largest welders, plus 85 percent of the third largest welder, plus 70 percent of the fourth largest welder, plus 60 percent of all remaining welders.
Exception: Percentage values lower than those given in (B) shall be permitted in cases where the work is such that a high-operating duty cycle for individual welders is impossible.
FPN [Linked Image]uty cycle considers welder loading based on the use to be made of each welder and the number of welders supplied by the conductors that will be in use at the same time. The load value used for each welder considers both the magnitude and the duration of the load while the welder is in use.
Even under high-production conditions, the loads on transformer arc welders are considered intermittent; therefore, it is permissible to reduce the ampacity of feeder conductors supplying several transformers (three or more) to the allowable percentages permitted in 630.11(B). It is obvious that intermittent transformer arc welder loads would be considerably less than a continuous load equal to the sum of the full-load current ratings of all the transformers. See also 630.31(B). The ampacity of conductors supplying welders is based on the I1eff rating on the welder rating plate. If the I1eff rating is not available, the size of supply conductors to welders may be calculated. The calculation is done by selecting the appropriate factor from 630.11(A) based on the type of welder and duty cycle of the welder. The selected factor is then multiplied by the primary current rating from the welder rating plate to determine the minimum ampacity of the supply conductors.
Obsolete terms and ratings such as nameplate and 1-hour duty cycle were removed from 630.11 in the 1999 NEC. The terms I1eff and I1max were added to the marking requirements. A new FPN includes a formula for I1eff, which is preferred over the value derived from using the factors in 630.11. The calculated value is still allowed. I1max is basically the same as the rated primary current.

Mark Heller
"Well - I oughta....." -Jackie Gleason

#72045 - 11/17/06 07:30 AM Re: welding receptacles... how many?  
IanR  Offline
Joined: Dec 2004
Posts: 328
Palm Bay FL USA
As the others have said, you can most likely put many outlets on the one circuit. Don't let the 6-50 plug on the welder throw you off.
Case in point. I have a Hobart Handler 180 amp MIG with a NEMA 6-50. It has a 12 guage cord because it only draws 19 amps max. It just came the 6-50 because it is kind of the default plug for welders, not necessarily because of the ampacity needs of the unit.

#72046 - 11/17/06 01:38 PM Re: welding receptacles... how many?  
u2slow  Offline
Joined: Sep 2003
Posts: 200
Salt Spring, BC, Canada
All good replies. [Linked Image]

I'm well versed in Section 42 of our CEC. From what I gather, it pretty much mirrors the intent of the NEC article.

This is an automotive hobbiest customer. (I suffer from the same affliction [Linked Image] The welder & plasma machines haven't been spec'ed. I'm basing the realistic maximum on what I've come to know with my own hobby, and dealing with the needs of a few automotive shops.

I've seen many installations with multiple 6-50R's on the same circuit. (machines with primary current in the ~40A range) I just wasn't sure if its considered acceptable practice depending on the situation, or permissable at all.

I can do it for this lower price and it may trip, or for more money I can separate them and prevent any possibility of a trip.

Good point. Now what do you respond when you get "Well, a professional should know these things" for an answer? [Linked Image] This is popular answer for most questions. Sometime I wonder why I continue to do work for this fellow. LOL!

[This message has been edited by u2slow (edited 11-17-2006).]

#72047 - 11/17/06 08:01 PM Re: welding receptacles... how many?  
e57  Offline
Joined: May 2003
Posts: 2,876
Now what do you respond when you get "Well, a professional should know these things"

Do you own a label maker? Right after you get done telling hime the limitations of the circuit, and explaining it the first time - you print up lables to the effect of "This circuit is 50A max, and has multiple locations - to avoid nuisance tripping combined usage must be below 50A." and place that on each cover-plate. You may want to include the panel and breaker number for those days when no one can read until after the fact.... [Linked Image]

Mark Heller
"Well - I oughta....." -Jackie Gleason

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