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Old 07-02-2008, 05:48 PM   #1
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Grounding for detached all-metal garage


Hi.

I've researched grounding requirements and NEC code extensively for detached garages. I am adding a 60-amp subpanel into an existing garage about 70' from the main service entrance panel, and won't go into extreme detail, but the subpanel will have its neutral isolated from ground, and the ground bus will be bonded to the subpanel, and a separate ground rod for the ground bus will be added for lightning protection.

The questions that I can't find answers for concern the fact that the garage is all METAL; steel I-beam construction with aluminum walls. So:

1. Should the metal garage be grounded by bonding it to the subpanel, either by direct installation to the interior walls of the structure, or through a bonding strap from the subpanel to the metal walls, thereby tying the whole structure to ground ?
OR
2. Should the metal garage be grounded by bonding it to the new grounding rod via a bonding strap, thereby tying the whole structure to ground?
OR
3. Should the metal garage be completely isolated electrically by using insulated backing boards to mount the subpanel in the metal garage, using non-metallic junction/switch boxes, using nothing but grounded plugs and wiring with a separate ground, etc).

I can't find any answers at all regarding the grounding of a detached metal garage.

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Old 07-02-2008, 06:09 PM   #2
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Grounding for detached all-metal garage


1 or 2 and drill and tap a lug on your structural steel not the walls. Run a jumper from your ground bar to your lug. 250.32, 250.50, 250.52

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Old 07-02-2008, 06:22 PM   #3
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Grounding for detached all-metal garage


Structural steel and building steel are certainly in the NEC.
See the Articles quoted above plus 250.104.
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Answers based on the 2008 & 2011 NEC.
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Old 07-03-2008, 08:31 AM   #4
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Grounding for detached all-metal garage


k, thanx. I'll check out the references.
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