Busway Feeder size

[John Dundon]

I am currently feeding a 480V 3-wire 400 amp busway with set of parallel 3/0 THHN conductors which gives me a total ampacity of 400A @ 75 deg. The busway is providing power to various CNC machines. Do I have enough copper?

 

[augie47]

Are your 3/0s in two separate conduits or all in one

 

[John Dundon]

Good question, the wires are in two separate conduits.

 

[infinity]

#3/0 THHN @ 75? C = 200 amps

200 * 2 = 400 amps

 

[augie47]

Baring some unforeseen element such as ambient or voltage drop, I see no problem.

 

[John Dundon]

First timer and I like this forum.

First timer and I like this forum.

Thank you for the input. I had one of those over thinking it moments. I was thinking that because the loads of this busway had motors that I would need to be 125% for the feeders to the buss. I will do that calc from the busheads to each machine.:thumbsup:

 

[ron]

Thank you for the input. I had one of those over thinking it moments. I was thinking that because the loads of this busway had motors that I would need to be 125% for the feeders to the buss. I will do that calc from the busheads to each machine.:thumbsup:

The Busway is part of the feeder so if the busway is 400A, then the conduit/wire should be 400A