oc protection for motor branch circuit conductors

[rjp]

I understand how to size conductors supplying a motor as directed in article 430 of NEC as well as the max. breaker size noted in table 430-52. It would be permissable to have a branch-circuit short-circuit and ground fault protection to have the overcurrent rating greater than the ampacity of the conductor. I'm not discussing Firepump motors, and the like.

Questions 1) Is there any restriction on the length of those conductors that have only the short circuit and groung fault but no overcurrent protection ahead of any controller or motor from a distribution board?

 

[augie47]

welcome to the Forum.


No NEC restriction.
You might want to note the Voltage Drop FPN in 210.19

 

[mcclary's electrical]

Welcome tothe forum, those conductors could be unlimited length (minding VD)

 

[rjp]

2nd part

2nd part

2) With a VFD in the equation;
a) Is it still permitted to size the breaker in a distribution board ahead of the VFD based on table 430.52 nec 2008? Does the VFD illiminate the need to size this breaker based on this code?
b) Is it necessary?

 

[don_resqcapt19]

Take a look at 430.122 for the VFD supply conductors.

 

[rjp]

Thanks all