Control Transformer Tap Conductors

[dwpelland]

My project is to control a 100HP motor. I have sized the conductors going from the branch circuit breaker to the contactor to be 1/0. I need to tap the branch circuit either at the load side of the breaker or the line side of the contactor to feed my 150VA control transformer with fused primary. Does anyone know of a minimum wire size restriction for the tap conductors, other than normal ampacity for the control circuit load? My co-workers say there is a restriction, based on the size of the main branch circuit conductor, but I can't find any such thing in NEC. UL508 31.4.3 may apply, but I'm not sure. Your expert opinions are greatly appreciated.

 

[buddhakii]

check out 430.72(C).

 

[benaround]

dwpelland, Article 240 has the rules for taps, 240.21(B)(1) and (2) is a good place to start.

 

[buddhakii]

In this case you would look in article 430 .