Welding Circuit

[wmeek]

I am trying to calculate a circuit for a arc welding machine.
What I have is Nameplate of 480V, 18.9A , Duty Cycle 60%.
So If I take 18.9A x .78( 630.11(A))=14.74 x 200%=29.48A go up to 30A breaker. The wire size can be #10 thhn. Is this correct or am I missing something else.

Thank you

 

[A/A Fuel GTX]

I would say you have it correct......

 

[iwire]

I am trying to calculate a circuit for a arc welding machine.
What I have is Nameplate of 480V, 18.9A , Duty Cycle 60%.
So If I take 18.9A x .78( 630.11(A))=14.74 x 200%=29.48A go up to 30A breaker. The wire size can be #10 thhn. Is this correct or am I missing something else.

Thank you

For the conductors

18.9 amp welder @ 60% duty cycle = 14.74 amps for the conductor size.

310.16 tells us that 14 AWG has a 20 amp capacity.

For the breaker

18.9 x 2 = 37.8 amps. (Use the nameplate amps, not the amps after the duty cycle multiplier)

You may even round up to the next standard size breaker

So per the NEC you could use 14 AWG with a 40 amp breaker to supply this welder.

Of course 10 AWG with a 30 amp breaker is allowed as well.

 

[wmeek]

For the conductors

18.9 amp welder @ 60% duty cycle = 14.74 amps for the conductor size.

310.16 tells us that 14 AWG has a 20 amp capacity.

For the breaker

18.9 x 2 = 37.8 amps. (Use the nameplate amps, not the amps after the duty cycle multiplier)

You may even round up to the next standard size breaker

So per the NEC you could use 14 AWG with a 40 amp breaker to supply this welder.

Of course 10 AWG with a 30 amp breaker is allowed as well.

So if you use the nameplate amps x 200%, How can you use a 30 Breaker.

Just Curios
Thanks

 

[iwire]

So if you use the nameplate amps x 200%,

Read 630.12(A) and you will see it says 'not more then 200% of rated primary current which in your case is 18.9.

How can you use a 30 Breaker.

I am not following you.

630.12(A) allows a breaker up to 200%, it does not require it.

Just Curios
Thanks

Not a problem, ask any questions, thats what the forum is about.