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Main Disconnect in Garage


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Hello,

I inspected a home where the main disconnect was in the detached garage. This panel had its own grounding electrode. The panel in the home also had a grounding electrode. Should the panel in the home be seen as a down-stream (sub-panel) and have a floating neutral buss and separate grounds and neutrals. If you are aware of any other issues with this arragnement please feel free to comment. Pictures are included for your review. Thank you in advance for your assistance.

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I see a 4-wire feeder leaving the main disconnect panel. But I see only a 3-wire feeder entering the bottom of the breaker panel. That is enough for me to call for an electrician to check this out.

In my area, that would be wrong, but your local authority might have his own rule book.

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Yeah,

Power into the main is 4 conductor and leaving is three. Since the main house has more than one branch circuit that buildling must have it's own service grounding conductor and service grounding electrode system but it can only be fed by a 3-wire if there are no other conductive paths between the two structures - no metal fence, no water piping, no concrete sidewalk, no telephone or cable lines. If I got that right, if there is a conductive path between the house and the garage the cable feeding the house from the main disconnect should be a 4-wire.

Hunkering down now and preparing to get slammed by Jim K. or Douglas 'cuz I know I've probably got some aspect of this wrong again.

ONE TEAM - ONE FIGHT!!!

Mike

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Hello,

I inspected a home where the main disconnect was in the detached garage. This panel had its own grounding electrode. The panel in the home also had a grounding electrode. Should the panel in the home be seen as a down-stream (sub-panel) and have a floating neutral buss and separate grounds and neutrals. If you are aware of any other issues with this arragnement please feel free to comment. Pictures are included for your review. Thank you in advance for your assistance.

Yes, the neutrals should be isolated in the sub panel. It's correct to have separate grounding electrodes at each building.

I see a 4-wire cable leaving the disconnect box but I see 3 individual conductors in conduit entering the sub panel. What happens in between?

Is the enclosure bonded at the service disconnect? I can't quite tell.

The pictures aren't clear enough for me to see much else. In the sub panel, it looks like there's a white wire that should re-identified and, if I were inspecting the panel, I'd look carefully at the arrangement of the black & red wires on all those MW circuits on the left.

Also, do I see double tapped neutrals?

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If I were to guess I would say the SER is feeding the disconnect and the SE is feeding the panel. Maybe someone had some leftover SER and used it instead of SE-U cable.

SER: Service Entrance Riser?

SE: Type SE cable?

SE-U: ?

Marc

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Something is amiss. SE cables at the disco, individual conductors at the main lug panel.

How do you figure that something is amiss? SE takes power to the disc then individual conductors take it from there to the panel.

Marc

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Something is amiss. SE cables at the disco, individual conductors at the main lug panel.

How do you figure that something is amiss? SE takes power to the disc then individual conductors take it from there to the panel.

Marc

There are no individual conductors in the disco. There is an SER cable and an SE cable.

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Yeah,

Power into the main is 4 conductor and leaving is three. Since the main house has more than one branch circuit that buildling must have it's own service grounding conductor and service grounding electrode system but it can only be fed by a 3-wire if there are no other conductive paths between the two structures - no metal fence, no water piping, no concrete sidewalk, no telephone or cable lines. If I got that right, if there is a conductive path between the house and the garage the cable feeding the house from the main disconnect should be a 4-wire.

Hunkering down now and preparing to get slammed by Jim K. or Douglas 'cuz I know I've probably got some aspect of this wrong again.

ONE TEAM - ONE FIGHT!!!

Mike

Mike,

That was the case for many years, but so many electricians got it wrong that newer editions of the NEC (starting in '08 I believe) require a 4-conductor feed to separate buildings in all cases for new work. The exception remains for existing work as long as the criteria you listed are met.

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