Dangers of bonding grounds and neutrals

[ActionDave]

It would be better, yes, but the electric utilization industry isn't always in sync with the electric distribution industry. The utilities insist on bonding their neutrals to their meter enclosures. And the NEC insists that we bond the neutral at the service disconnect. And neither is going to give.

If we could just start our EGC from the meter neutral, then we wouldn't need the MBJ and all of our neutrals would be insulated from ground.

We do, do that if we put a service disconnect right next to the meter or use a breaker panel with a built in meter base.

BUT! There is no NEC requirement for a meter at all. So, Maybe we could insulate the neutral at the meter and use a MBJ at the disconnect and take an EGC back to any meter that might be installed? The utility is NOT going to rely on us to ground their equipment. So we just live with it.

If you substitute a CT cabinet where you are talking about the meter you get power company engineers and local inspectors screwing this up all the time. I have seen an extra green wire pulled from the panel with the MBJ back to the CT can more than once.

 

[Seven-Delta-FortyOne]

I think the thing you are missing is, before the MBJ we use a 3 wire cable.

Feeders are 4 wire.

There is no EGC in an SE cable.

 

[kwired]

And the NEC insists that we bond the neutral at the service disconnect. And neither is going to give.

NEC requires bonding all items containing service conductors to the grounded service conductor. EGC technically only exists beyond the service disconnecting means as it is furthest point from the source where the grounded conductor is bonded.

 

[wwhitney]

I don't see a downside. The meter neutral is typically factory bonded to the enclosure so if you called that the MBJ and just installed an EGC from that point on electrically there is little difference.

That would be a convenient option when the meter supplies multiples service disconnects; putting a single MBJ in a gutter after the meter would also be a convenient option. The single common MBJ would avoid the creation of grounded conductor - EGC loops that lead to the creation of "unavoidable objectionable" current with the current rule of one MBJ per service disconnect. Too bad the NEC doesn't provide the allowance.

Cheers, Wayne