electric arc welder

[puzzler]

I would like to clarify with anyone that i'm am sizing my conductors and ocpd for a residential welder correctly.
The name plate states that the primary current is 48 amps, the supply is 240 VAC and the duty cycle on the lower amp range is 100% and 20% on the higher amp range(120 - 230amps).
Using article 630 for ampacity of supply conductors, i assume i would use 100% duty cycle in table 630.11(a) giving me primary current x 100% = 48 amps.
For the ocpd 630.12(a) states that it should not exceed 200% of the primary current - 48 x 200% = 96 amps (use a 90 amp breaker).
I would like to know is this correct or could you use a smaller breaker because the welding plug is a three prong 240V 50 amp plug on a number 10 awg cord to the welder. Could you use a 50 or 60 amp breaker?
Any help would be appreciated.

 

[bennie]

Re: electric arc welder

It all depends on the size of rod you are burning.

 

[gregory]

Re: electric arc welder

630.31 Ampacity of Supply Conductors.
The ampacity of the supply conductors for resistance welders necessary to limit the voltage drop to a value permissible for the satisfactory performance of the welder is usually greater than that required to prevent overheating as described in 630.31(A) and (B).
(A) Individual Welders. The rated ampacity for conductors for individual welders shall comply with the following:
(1) The ampacity of the supply conductors for a welder that may be operated at different times at different values of primary current or duty cycle shall not be less than 70 percent of the rated primary current for seam and automatically fed welders and 50 percent of the rated primary current for manually operated nonautomatic welders.

Automatic and seam welders require a larger conductor for the supply because they are operating continuously. They require a 70 percent rating. The resistive welder that is common for homes only require a 50 percent supply rating. so 48 amps times .5 would equal 24 amps. # ten wire would provide you an ampacity of 30 amps. The reason for this is because small hand held welders are only used for brief periods of time.
Fusing should not be larger than 50 amps on Number ten wire

 

[bennie]

Re: electric arc welder

I have a Lincoln transformer welder. I can burn up to 1/8 inch rod with the primary on a 30 amp breaker. Welding current is about 110 amps.

[ June 04, 2003, 10:24 PM: Message edited by: bennie ]

 

[puzzler]

Re: electric arc welder

Thanks for your reply Gregory.
So even that the welding machine say's that is an arc welder, it is classed as a resistance welder in the code book?
The welder has a manual current setting lever on it and like it say's it for home use which means it will only be operated at different times and current settings.
Was there a rule that you used for sizing the ocpd or because it has a 50 amp plug on the welder ,you would generally use a 50 amp breaker?