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pont89
Jul 1, 2008, 04:06 PM
Questions concerning the need or requirement for a bonding wire from the panel board to the meter under the following setup.

Main breaker panel board with system grounded at the meter. The branch circuits, all in conduit, have equipment grounds connected to an EG bar in the panel board. The neutral wire is bonded to the board with the bonding screw. Rigid is used from the board to the meter. There is no bonding wire from the EG to the meter. I thought I read, some time ago, that the conduit could be used as an EG.

Questions- A) Is a bonding wire from the EG to the meter required in the above case, or, B) does the rigid serve as an EG, C) since the neutral is bonded to the board and the neutral connected to ground at the meter, is that sufficient, or D) would it be a best practice to use a bonding wire? Thanks……

KISS
Jul 1, 2008, 05:52 PM
The key here is, how and where is the system neutral tied to the single point ground. Conduit can be used as protective ground, but not the ground bonded to the neutral and connected to the ground rod or other building grounding mechanism.

pont89
Jul 1, 2008, 06:22 PM
Kiss, the system neutral is tied to ground in the meter box-the ground wire is connected to the same lug as the neutral for the service drop and service entrance. The wire then runs through 1/2" conduit. The conduit is connected to the meter box and at the other end both the wire and condiut are connected to the ground rod. If I understand your answer correctly, the set up is OK and the conduit is the bonding the panel to the meter?

KISS
Jul 1, 2008, 08:34 PM
I'm confused too reading your last post.

The neutral/ground-rod bonding is usually done after the meter at in the enclosure where the first disconnect is.

Example #1:
Main panel with main breaker, no outdoor disconnect
... Ground bus connected to round-rod
... Neutral connected to Neutral
--Ground and neutral busses tied together

Example #2
Optional main breaker in main panel. Outdoor disconnect just after meter
... Ground-rod connected to neutral
... Neutral connected to main panel
... Ground connected to main panel ground
... Neutral and Ground bars are separated at the main panel. Bonding jumper is not installed. It doesn't matter if the disconnect and the main panel are connected with metal conduit.

You may have something funny where the ground and neutral bus bars should be isolated at the main panel.

You DO NOT want the ground/neutral bond to occur in two places. If they are occurring in the meter and the panel, that's wrong.

tkrussell
Jul 2, 2008, 02:53 AM
Kiss, the neutral can be grounded at any or all of the following locations, service transformer, meter, and at the Main Service Disconnect, as per NEC Section 250.24.

I see no issue with the arrangement that Pont89 describes, other than the rigid conduit from the meter to the panel contains service entrance conductors, and while is allowed to be an equipment grounding conductor, must also be bonded to the neutral/ground by using a bonding bushing with a lug to connect a grounding/bonding jumper.

If that exists, then Pont89 is all set.