# Subservice grounding



## hueco44 (Mar 7, 2011)

Finishing up a 200 amp, residential service upgrade and discovered I don't remember the grounding requirements! Ran 4-0 "quadraplex" from a 200 amp disconnect to the new main-lug panel and a #6 wire from the disconnect to a ground rod.

Question is, does the #4 primary ground (water pipe) run from the disconnect to the water service entry or from the service panel or what? It is about a 60 foot run from the disconnect to the water entry and I hate to waste the money and materiels on unnecessary wiring.

Also, does the sub-panel have to be grounded other than the fourth wire (ground wire) from the disconnect?

Thanks.


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## Hippie (May 12, 2011)

Grounds/ bond all made at disconnect


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## hueco44 (Mar 7, 2011)

Thanks! Can (would) you remind me of the reasoning behind separating the neutrlas and grounds at the sub?


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## Hippie (May 12, 2011)

Are you an electrician??


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## hueco44 (Mar 7, 2011)

Yes, but old enough to be forgetting some details behind the technique. I'm betting you'll get here. Hope you don't.

I am assuming the separation is to facilitate a good conducting path back to the disconnect for ground faults, but I also don't recall any options when, for example, EMT is used between the service panel and disconnect.


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## Meadow (Jan 14, 2011)

While the code is not specific about why seperate grounds and neutrals are required, there is reasoning behind it. It has nothing to do with making a fault clear faster, a neutral can do the same. It has to do with avoiding parrellel current paths on metal objects (causes EMFs and inductive heating of ferrous conduit) hence the requirment of not bonding neutral to ground in a subpanel and to eliminate the shock hazard of an open neutral. If the neutral opens to or at your subpanel with them split you simply get a voltage imbalance on loads, however if the neutral to the panel does both grounds and load neutrals and it was to open then you end up with an energized ground system as well (metal cases of tools are energized relative to normally grounded items (water pipes, earth, appliances on a different panel ect)


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