Combo Box Grounding

[Duncan8943]

I've got a 100A combo meter base/disconnect box. This is to be used as a temporary service. The box has a neutral bar with a bonding screw and a seperate ground bar. Is there a difference between (1) Tying the ground wire to the ground bar and bonding the neutral bar to the panel or (2) Tying the ground wire to the neutral bar and bonding the neutral bar to the panel. Normally, I would tie the ground wire to the neutral and then use the bonding screw.

 

[texie]

I've got a 100A combo meter base/disconnect box. This is to be used as a temporary service. The box has a neutral bar with a bonding screw and a seperate ground bar. Is there a difference between (1) Tying the ground wire to the ground bar and bonding the neutral bar to the panel or (2) Tying the ground wire to the neutral bar and bonding the neutral bar to the panel. Normally, I would tie the ground wire to the neutral and then use the bonding screw.

Either way is compliant from your description of the situation. The "ground wire" you mention I assume you mean an EGC on the load side. There is no EGC on the line side to the POCO xformer. You must have a neutral from the POCO xformer to the meter combo which must connect to the neutral bar (the neutral at a service cannot connect to a separate EG bar as the then enclosure would be carrying neutral current). In this application you are free to connect EGC's on the load side to the neutral bar or the EG bar. Of course, as you mention, the neutral bar bond screw must be installed.

 

[Volta]

As I read it, you must connect the GEC to the bar that contains the grounded conductor (neutral) rather than a secondary bar simply bolted to the enclosure.

Grounding Service-Supplied Alternating-Current Systems.

(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).

(1) General. The grounding electrode conductor connection shall be made at any accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.

 

[don_resqcapt19]

This is a perfect example of why we need to be using the correct terms in the questions and answers. One reply was based on "ground wire" meaning Equipment Grounding Conductor and the second on "ground wire" meaning Grounding Electrode Conductor.

 

[texie]

This is a perfect example of why we need to be using the correct terms in the questions and answers. One reply was based on "ground wire" meaning Equipment Grounding Conductor and the second on "ground wire" meaning Grounding Electrode Conductor.

I agree, and I thought I used the correct terms based on how I understood the OP. But now that you mention it, maybe he was referring to the GEC, which would have to connect to the actual neutral bar and not the equipment ground bar (if he is using one)

 

[ceb58]

Go with #2. Take the ground bar out and save it for hard times.