Sub-panel, separate building

[102 Inspector]

I have a project I inspected that has the main disconnect located on the side of a building 60 feet from new building. A 4-wire was run from disconnect into panel in basement of new structure. Contractor bonded grounded conductor and grounding electrode conductor at "sub-panel" in new building. He is stating that since the new panel has a main breaker, that is the way it needs to be completed instead of isolating neutrals and grounds. Sadly, we are still under the 2008 NEC. What is the best way to explain to him that they not to be separated after the main disconnect switch, regardless of whether it is in a separate building.

 

[augie47]

I would reference 250.24(A)(5) and the reference to 250.32 emphasizing the exception to earlier Codes

 

[LarryFine]

He's wrong. When a feeder includes separate neutral and EGC, bonding them at the load end creates a parallel pathway for neutral current. That is never permitted to occur.

If they were meant to be tied together, then there would be no separate EGC; everything intended to be grounded would be bonded to the neutral, just as with a service.

 

[infinity]

Sadly, we are still under the 2008 NEC

2008 is the code cycle that no longer permitted 3-wire feeders with bonded neutral to a separate structure so your electrican is incorrect. Bonding the neutral with a 4-wire feeder will allow the neutral current to flow on the EGC.

 

[LarryFine]

A 4-wire was run from disconnect into panel in basement of new structure.

I should have asked: Is this feeder 1ph with an EGC or 3ph without an EGC?

If it's the former, my response applies; if the latter, there should be an EGC.

Either way, the remote panel is a sub-panel, and should be wired as one.