Multiple Meters, One Service

[mhulbert]

I am working on an old commercial building that is being converted to underground service. We are installing all new 400A service, meters, feeders, and subs. I am questioning my boss on the grounding of he service.

We have a 4" PVC conduit (service lateral) going into a termination cabinet. From those lugs, we are taking 500MCM in to a "Bus Duct". Below this are 2 meter/mains, a 100A and a 200A and space for a future 3rd meter main. These meter mains are actually bolted to the bus duct. There is no conduit between them. It is setup for this from B-Line. So they are essentially the same box once they are totally bolted together. Boss wants to connect ground rod and the bus duct enclosure to the neutral bus bar in the bus duct. he wants to leave the meter/mains G-N bonded as well.

I think this is wrong because some of the neutral current will split at the meter/main bonds and go through the enclosures back to the bonding jumper in the bus duct. Am I right? I've never done a service with mor than one meter, so I am unsure of this.

Thanks, this is an awesome forum.
Mike

[ April 29, 2004, 10:08 PM: Message edited by: mhulbert ]

 

[websparky]

Re: Multiple Meters, One Service

Hi Mike,

I think I understand.....
One question, in this "meter assembly" is there a "main" breaker attached to the load side of the meters?

 

[mhulbert]

Re: Multiple Meters, One Service

Oooops, I meant to say there is a main after the the meter, but no main on the service...in the "bus duct" there are 3 bars- L1, L2, N. (This is 120/240 1 pahse). The bars are drilled and tapped and there are 4 lugs on each. 3 lugs are for the meter mains (Wire goes from lug--->Meter socket--->Breaker--->out to feeders)
There are big lugs for the incoming service, and the neutral bar has a fifth lug for ( I think) a bonding jumper. The meters have a removable bonding screw, but no seperate grounding lugs at all (just 3 neutral lugs). I can't see an easy way to run a seperate ground from each meter back to this can, but the current installation doesn't seem right to me. Oh yeah, the bus duct will be sealed by the utility, since it is before the meters (Don't want anybody taking advantage of those extra lugs now!)

Mike

[ April 29, 2004, 10:58 PM: Message edited by: mhulbert ]

 

[Ed MacLaren]

Re: Multiple Meters, One Service

In my opinion, you are correct.

The grounding electrode conductor (GEC), and the main bonding jumper to the enclosure, should be connected to the neutral bar in the "splitter" section.
The neutrals in the meter sections should be isolated from the enclosures by removing the bonding screws.

If these meter sections were connected to the "splitter" section with PVC nipples, they would require equipment grounding conductors, (EGCs) but not here, as they are bolted to the splitter section, and this connection serves as the EGC.

Ed

 

[don_resqcapt19]

Re: Multiple Meters, One Service

Bonding at multiple points is permitted on the line side of the service disconnect. This is very common even in single meter services. The grounded conductor is bonded at both the meter can and the service panel. Yes, this will place any metallic conduit between the meter and the service disconnect in parallel with the grounded conductor, but is permitted by the NEC. See 250.142(A).
Don