3 phase and the NEC

[mrgarm13]

Okay, before we begin, let it be clear that I do not have all the information here. So my following question is not mine or how this even happened.

My dad is remodeling his shop and the time is arriving to wire the 3 phase air compressors back up. The electrician we hired said that he cannot go from the service entrance box directly to the motor controllers, he has to go through the circuit breaker box before he can go anywhere else. My father disagree's and cannot see why the NEC would require such a thing.

So I suppose I am looking for the part of the code that says "3 phase conductor's must be wired through the central box."

 

[George Stolz]

Since you've hired an electrician, I do not consider it a DIY question.

The electrician is most likely correct, 240.4.

 

[mrgarm13]

Sorry to the moderator for the double post.

 

[suemarkp]

What is the "Service Entrance box"? Is it a meter enclosure, a junction box with no other devices, a disconnect with a single large 3 phase circuit breaker?

You need overcurrent protection on those conductors to the motor controller.
That overcurrent device needs to be appropriately sized (can't terminate a 30A circuit on a 200A breaker unless you can meet all the restrictions in the "tap rules").
Is there a separate set of lugs for this motor controller circuit to terminate to (you can't land two conductors in most lugs, but there are some solutions for that).

 

[nicholaaaas]

I'm gonna be inclined to agree with the electrician and not your dad

Sent from my SM-T217S using Tapatalk

 

[kwired]

Okay, before we begin, let it be clear that I do not have all the information here. So my following question is not mine or how this even happened.

My dad is remodeling his shop and the time is arriving to wire the 3 phase air compressors back up. The electrician we hired said that he cannot go from the service entrance box directly to the motor controllers, he has to go through the circuit breaker box before he can go anywhere else. My father disagree's and cannot see why the NEC would require such a thing.

So I suppose I am looking for the part of the code that says "3 phase conductor's must be wired through the central box."

Lets just say that the conductors supplying this air compressor need a proper level of overcurrent protection on them. There may be conditions where that level of protection could vary, like say a feeder tap situation, but there are limitations on length and size and other unknown factors may come into play. More information really is necessary to give an accurate answer, but in general the electrician mentioned is probably on the right track.

 

[Smart $]

Lets just say that the conductors supplying this air compressor need a proper level of overcurrent protection on them. There may be conditions where that level of protection could vary, like say a feeder tap situation, but there are limitations on length and size and other unknown factors may come into play. More information really is necessary to give an accurate answer, but in general the electrician mentioned is probably on the right track.

Exactly... but more specifically, I think his dad is wanting to tap the service entrance and run directly to the controllers. That would require the controllers be listed and installed as service equipment. Also must be located outside or inside nearest point of entry. This is an entirely feasible scenario if you think in terms of an MCC used as service equipment... but I'm doubting this to be the case.