NEC?? Are you able to run a Tap from a motor control circuit? ?

Question

I am looking to run a tap from 400A Main incoming breaker which load side would power a 200Hp VFD with a 125A panel tapped off off that breaker line side. I plan on doing this using the 10FT tap rule 240.21(b). But does this fall under some other motor Tap rule since the primary function of the feed is designed to operate a motor? Would I need to look at the overload of the Motor and figure the feed cable sizing off of that plus the panel? Or would it simply be 525 Amp sized feed lines because of the full output of the Incoming breaker and Panel .

I believe I will be using Parallel 300MCM with a 1/0 GND.

Am I able to do this??

Answer 1

You have a 400A main breaker with a tap to a 200HP VFD and a tap to a 125A panel?

The 125A panel has a motor too?

I'm a little confused with your explanation.

From the load side of a 400A breaker you may run a wire to a 125A breaker.

This would be a tap and the wire would be sized for 125A, but it must not be longer than 10 feet.  

Normally we think of the load side wire being sized based on the over current protective device.  In this case the probability that there will be a fault between the 125A breaker and the 400A breaker is minimal, hence the 10ft rule. And why you don’t have to use 400A rated wire to a 125A breaker.  Plus it wouldn't fit.

I’ll check back later to see if  you need more help, if you clear up some of your explanation.