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Thread: subpanel ground rod location and installation

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    DIY scratch-pad engineer leejosepho's Avatar
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    Default subpanel ground rod location and installation

    I plan to install a subpanel for my garage and new workshop, and I understand the bonding issue and that it must have its own ground rod. The new panel will be located about 12' in from an exterior wall.

    Am I correct in thinking the ground rod must be either right next to an outside wall or actually outside?

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    The ground rod can be on the other side of the building as far as code is concerned.

    Is the panel going to be 12' inside the building? If so then you need a disconnect outside or just inside the structure. Same as with a main service.


    I assume this is a detached building?

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    The ground rod can be on the other side of the building as far as code is concerned.
    Okay, but can it go down through the slab floor *inside* the building or does it have to be outside?

    Quote Originally Posted by Speedy Petey
    Is the panel going to be 12' inside the building?
    ...
    I assume this is a detached building?
    No, our garage is attached to the house and the new workshop is behind the garage. Depending upon the actual location to be selected, the panel could be as close as 6' from an outside wall. My overall assumption here is that the ground rod has to be outside the structure altogether, but I would put it down through the floor (How far from outside?) if that is acceptable.

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    Quote Originally Posted by leejosepho View Post
    No, our garage is attached to the house and the new workshop is behind the garage.
    Are you saying the garage is attached and the workshop isn't?
    Just my 2 worth.

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    Yeah, hold on! Is the garage attached and the shop not, or are both attached???

    If the panel will be in the garage, or both are attached, then NO ground rod is required, needed or wanted. Same with the disconnect/main breaker.


    MORE details please.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Please pardon the confusion.

    The garage is attached at the East side of the house, and the new workshop is attached to the North wall of the garage and it also overlaps the house by four feet. Our main panel is in the basement at the opposite corner of the house, and there are presently no circuits going to either the garage or the workshop.

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    Then NO ground rods are needed or wanted for this sub-panel, and you can install a main lug panel anywhere you want.

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    Hey Lee, is this what you look like after you shave?

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    DIY scratch-pad engineer leejosepho's Avatar
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    Nope. The real me only has 10 teeth ...
    Last edited by leejosepho; 10-22-2007 at 02:26 AM. Reason: remove picture

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    Then NO ground rods are needed or wanted for this sub-panel, and you can install a main lug panel anywhere you want.
    Okay, so what about bonding? When I put a panel in a detached garage at another place several years ago, I was told to not bond it and to install a ground rod ... and I had been assuming I would have to do the same here.

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    You then had a detached structure fed by a three wire feeder.

    You now have an attached structure sub-panel and MUST run a "4-wire" feeder.
    In the sub-panel the neutral bar is NOT bonded to the panel box and you must add an additional ground bar.
    The neutrals are ground must remain isolated.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Okay, thank you!
    Attached Images Attached Images  

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    You now have an attached structure sub-panel and MUST run a "4-wire" feeder.
    In the sub-panel the neutral bar is NOT bonded to the panel box and you must add an additional ground bar.
    The neutrals are ground must remain isolated.
    I have been searching other discussions here, and it looks like all four wires must be at least the same minimum size unless the subpanel is for a "balanced load" like a 240-volt dryer or water heater. Correct?

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    No. The neutral can be downsized since this will be a 120/240v panel and at least some, if not much of the panel's load will be balanced.
    This is determined by the load calculation, but a general rule of thumb is two wire sizes smaller. NEC 220.61 is the code reference.

    The ground is sized according to NEC Table 250.122

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by leejosepho View Post
    ......unless the subpanel is for a "balanced load" like a 240-volt dryer or water heater.
    A dryer is NOT a balanced load. There are several 120v loads in a dryer. They are 120/240v as opposed to a water heater which IS a straight 240v load.

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