Welder hook-up

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guschash

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HO wanted his welder hooked-up, so I looked on the welder and it said input 230v/50amps. But in his manual it said use #10 and fuse at 50amps. Anything over 100' use #8 or larger but fuse at 50 amps. I think it should be 6/3 and 50amp breaker. Any thoughts.
 
It must be a spot welder to require that size of conductor, the current drawn by those is only for a short duration, so the wire does not heat up. The ones that I have hooked up were much larger (fused at 200 amps 480 volts) I don't remember the exact specs, but I believe it draws current for only a couple of cycles. Also use a fuse instead of a breaker as the breaker will trip on magnetic trip.
 
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480sparky said:
Even so, the allowable ampacity of #10 is only 40 amps. Then you start getting into 110.14(C)....
Click to expand...

I believe you can use a 70 amp OCPD (Max) for a #10 thhn under the 75 degree column---in a case where the #10 is being used for a welder circuit. I believe a 50A OCPD will work fine.
 
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240.4(G) has a table.
In the table you will see reference to 630.12 &.32.

.12 & .32 both permit overcurrent protection of conductors for welders at considerably higher than standard settings.

NOTE:
The principle is the same for motors and A/C.
If you take a look at Table 240.4(G), you will notice there are a number of locations in the NEC where standard overcurrent protection is not restricted to table 310.16.
 
After reading Atricle 630, its pretty simple. Primary current in amp ( name plate ) multipled by duty duty cycle. #10 thhn and 50amp breaker for the welder.
 
I think that you have the NEC requirements for this installation in hand. As a design issue, you might consider the following:
1) what sort of receptacle are you going to use?
2) in this particular setting, is there a reasonable chance that the customer will want to be able to plug in a different load?
3) can you 'upsell' pulling the larger conductors, so that the circuit will not be mismatched if something other than a welder gets plugged in?

IMHO it is _reasonable_ and _economical_ to install this as a welder only circuit, but also reasonable and possibly more profitable to install it as a 'general purpose' 50A receptacle. The choice should be customer driven.

-Jon
 
I am with Jon on this one just because it is permissible does not make it good design..I would design it so it can have multiple uses..I would wire it accordingly to a 50 amp breaker setup..
 
Definitely size the wire like you would for a normal circuit. I believe there's something in the NEC (there is in other codes) that requires you to follow the more stringent standards of the code or the equipment instructions.

Remember:
-Just because the one he has now calls for small wire, that doesn't mean the one he buys next week/month/year will

-Just because the one he has now is meant for spot welding or "intermittent use" doesn't mean they all are.

-If it burns his house down (even if he does something like what's mentioned above), there's a good chance YOU will be held responsible.

-CYA, man, CYA
 
I would simply let the customer know the situation and let them decide. It's their money not mine.

If they are happy with code minimum then so am I.

As Pierre said

240.4(G) has a table.
In the table you will see reference to 630.12 &.32.

.12 & .32 both permit overcurrent protection of conductors for welders at considerably higher than standard settings.
Click to expand...

That is correct, it is not unsafe, it is not hack.

There is a reason the NEC felt the need to have a complete article dedicated to welders, don't be afraid to take advantage of it. :cool:
 
guschash said:
What table are you using? Table 310.16 says 40 amps for #10.
Click to expand...

Please see what the others wrote after you asked this question.
;)

By the way, I was just responding to what 480 posted. What I posted is 100% true, yet you can design the branch circuit however you want--as long as your install meets code. Personally I would install a #8, and have done so in the past. ;)
 
I may have told you wrong, it's been 12 years since the last spot welder that I hooked up, so I got to thinking, I believe that I had to run 250 kcmil with a 200 amp fuse, spot welders are very finicky about voltage drop due to the short term high current draw, it was not calling for smaller, but larger. Also never run the feeder in EMT or ridgid steel conduit, use pvc as the metal conduit acts as a choke and cause the spotwelder to malfunction. Sorry about the incorrect info, like I said, its been a while, I'll get a run on a bunch of them, then not do any for along while.
 
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