Thread: Two Main Service Panels at single structure?

Ok, here is the setup. Service main panel located at the utility pole which is approximately 100 feet from the home. A 200 amp main breaker located in this panel. From there three cables are pulled into the home, through non-metallic conduit, to another panel located in the garage. No visible metallic connection could be located between the utility pole or the home. No visible cable lines, phone lines, etc, the house is in a rural area. The service at the utility has a GEC connected to a driven rod at the base of the utility pole.

In the garage the panel is installed just like another service main with a 200 amp main breaker. The neutrals and grounds are bonded at this panel and a GEC that disappears into the wall cavity that I could not trace any further.

So in essence, the system is installed as two service main panels.

If I understand 250.32 correctly this would be correct if there was no 2nd 200 amp breaker at the garage panel? Or is this correct as wired with two 200-amp breakers one located at the utility pole and one at the garage panel with the neutrals and ground bonded in both locations?

Again, I could not find any metallic bonding path between the utility pole and the home however that isn't to say definitively that none exists underground I could not see.

Recommendations? Thanks

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Based on your description, and assuming the house GEC is connected to an electrode, it's OK as wired.

Michael,

As I understand what you have:

From the 2008 NEC.
- 250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).
- - (A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
- - - Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non–current-carrying metal parts of equipment.
- - (Jerry's note: For (A) above, if there is a grounding electrode at the house and at the garage and they are connected as in (B) below, then that part is okay.)
- - (B) Grounded Systems. For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).
- - - Exception: For existing premises wiring systems only, the grounded conductor run with the supply to the building or structure shall be permitted to be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded where all the requirements of (1), (2), and (3) are met:
- - - - (1) An equipment grounding conductor is not run with the supply to the building or structure.
- - - - (2) There are no continuous metallic paths bonded to the grounding system in each building or structure involved.
- - - - (3) Ground-fault protection of equipment has not been installed on the supply side of the feeder(s).
- - - - Where the grounded conductor is used for grounding in accordance with the provision of this exception, the size of the grounded conductor shall not be smaller than the larger of either of the following:
- - - - - (1) That required by 220.61
- - - - - (2) That required by 250.122
- - (Jerry's note: For (B) above, if it meets (B)(1), and by your description it does; and if it meets (B)(2), and by your description it does; and if it meets (B)(3), and you did not say that it was GFCI protected at the service; then this part is okay.)

If I am understanding your description correctly, and you are meeting both (A) and (B), then it is okay.

Thanks, that is the way I understand it as well. My only concern is that I could not locate a driven rod at the main structure but the GEC was visible at the panel and routed through the bottom of the panel into the wall cavity. From there,,,,,,,,,

Thanks all.

The system sounds as though it complies. My only point is that I would try to determine whether there is a connection to the water service entrance (if it's metal) and if if it is plastic, is there more than 1 ground rod being used?, or some other available electrode?

Michael, Fred,

The way I always wrote that up was to have the electrical contractor verify proper system grounding "while on site doing other repairs", that way no one can complain that "the electrician made a special trip out just for that", and, if they did, I would point to my report and ask "and why did *YOU* have them make a *special trip* for that when *I* stated right here to have them verify that while on site making other repairs"?

Not going to blame that "special trip" on me and expect me to pay for it when they found the system was properly grounded - which is what I told them to verify to start with.

The house was a new walk-out basement style. The basement was completely finished throughout and the main water cutoff was behind a wall with one of those plastic access plates you can slide in to cover. I could see the water pipe was copper below the cutoff and PEX run thru the home.
I did the same in my report and recommended the electrician verify while making other repairs. Seemed the reasonable thing to do.
Thanks