Arc Welder

[Sonny Boy]

I'm installing a branch circuit for an Arc Welder. Nameplate info is 230 VAC single Phase. 45 Amps Rated Primary Current. 20% duty cycle. Non-generator type.

Referencing NEC 2008 Articles 630.11(A) and (B) and Table 630-11(A), I came up with this ampacity the for supply conductors.

45 amps rated primary current X 0.45 (factor from Table 630.11(A) = 20 amps. Minimum conductor size is #12 AWG (romex).

Reference NEC 2008 Articles 630.12(A) and (B).

This is where I get lost. How do I determine the size of the branch circuit overcurrent device?

Thanks for the help.

 

[augie47]

Look at 630.12... 200% of I max, and not more than 200% of conductor ampacity. Looks like a 70 amp max unless I'm mistaken.