400A 3 Phase Service

[Keith Geiser]

We installed a 400A 3 phase 120/208v service with 42 circuits. The main panel has a 400A Breaker with feed through lugs, feeding a second panel which is right beside it. It has 400A lugs and is also a 42 circuit panel. We installed the bonding strap on the 2nd panel. The inspector is saying we need to take the bonding strap off and split the grounds and neutrals. The reason I put the bonding sraps on both panels is because the 400
A main breaker feeds both panels so I figured it as one panel. Was this correct, or incorrect? Keith Geiser

 

[roger]

I agree with you, but that doesn't mean we'll win this argument, I see your conductors to the second panel simply as bus extensions. (that last part is for those that have been here awhile ) )

Roger

 

[amptech]

If the feed thru lugs on the first panel are disconnected from the power via the 400A main, then the first panel is the main disconnect and the conductors from the feed thru lugs to the second panel should be a 5 conductor feeder. You should not bond the neutral and equipment ground conductor in the second panel. It is my understanding that even if these 2 panels were chase nippled together they are still 2 separate panels and the conductors between them are feeders.

 

[benaround]

I agree with Roger, those are bus extentions of the same panel, under those

conditions.

 

[amptech]

If this is indeed an extension of a bus, how far can you go? Same situation but the second panel is say, 100' away on the other side of the building but within sight of the first panel? would this also be considered a bus extension? If not, what is the magic distance? I just can't get comfortable with this situation. Maybe a specific code reference would help me.

 

[infinity]

If this is indeed an extension of a bus, how far can you go? Same situation but the second panel is say, 100' away on the other side of the building but within sight of the first panel? would this also be considered a bus extension? If not, what is the magic distance? I just can't get comfortable with this situation. Maybe a specific code reference would help me.

This is an interesting question. IMO once the conductors leave the first panel and enter the second the grounds and neutrals should be separate. Can't think of a code reference either way. What article did the inspector cite?