welder question

[olly]

I have not had any experience doing welder calcs. I plan on digging in the codebook but Im sure I will be referring back here after. Customer has a big welder, nameplate says:

Input: volts 208/230/460

Input: amps 121/110/55

output 300amps

If I remember correctly you don't size breaker off the name plate.

Im not concerned with output obliviously. I want to size the breaker correctly along with the wire and plug. I will read up on welder calcs but would some one tell me what size breaker, wire and plug I need? Just to be sure I get it right. The supply voltage will be 240v.
Thanks for your help!!!

 

[suemarkp]

You need another number -- the duty cycle. That should be on the nameplate.

 

[olly]

60% duty cycle

 

[olly]

what exactly is a resistance welder? Does that mean a wire fed welder????

 

[suemarkp]

Assuming this is a non motor-generator arc welder, the duty cycle of 60% gives you a multiplier of 78% [NEC 630.11A]. So conductor ampacity is required to be 110 * .88 = 86A. It also can't be less than Ieff if you have that value on the nameplate. Branch circuit conductor overcurrent protection can't exceed 110A or 200% of Imax (if you have Imax on the nameplate). The breaker also cannot exceed 200% of the conductor's rated ampacity.

A resistance welder is like a spot welder (current is run though the item being welded to melt it). A wire feed welder would be an arc welder.

 

[olly]

thanks that helps a lot. Does the receptacle need to be rated for 110a also?

 

[J.P.]

Is it a mobile unit and has more than one recep?

Or can you wire it to a disconnect?

 

[suemarkp]

The receptacle only has to be rated at the modified ampacity [210.21(B)(1) and (3) exception]. So in your case, 86A or above.

Code used to require labeling these "welder use only" since the receptacle and wire are on an oversized breaker. I don't see that in the 2014 book though.