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Thread: Proper way to ground a metal build and sub panel?

  1. #1
    Join Date
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    Question Proper way to ground a metal build and sub panel?

    Calling FredK and mgrist and anyone else with knowledge.

    I'm getting ready to pull the wire through the conduit so I can depower and remove the overhead feed for the garages. I will be running 4 8ga wires for two 30 amp circuits. Two black, one white and one green. It will be feeding from a Cutoff Box that has two 30 amp fuses.

    I have is I driven two 8' half inch ground rods, 8 feet apart into the ground next to the building. I purchased clamps and 50' of 8 ga bare copper wire for the grounds. I planned to run them from the ground bar in the breaker box I mounted to one of the frame members of the garage.

    One thing I'm still contemplating is whether to run PVC conduit and pull wires for plugs and lights in the garage or use Armored Cable. I'm throwing that out there because I think it might affect other parts of this.

    So the question is do I attach clips from the bare ground wire to the building between the box and ground rods OR should I use 8 ga insulated wire to connect the box to the rods? My concern is if there a short and the ground becomes energized will it make the building dangerous/electrified?

    Also I think that the Cutoff Box on the house the ground and neutral wires are bonded BUT in the Breaker Box in the garage they should NOT be bonded. Do I have that right? I looked at the Breaker Box I have in the garage and I don't see a way to not have the ground and neutral wire connected unless I use the tapped hole to attach the ground wire. The photo of the Small breaker Box is from when I had it wired in the shed in Phoenix.

    Thanks for the help in advance. I wanting the to be done correctly and safely. The mess that was in both garages needs to be fixed.
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    Last edited by Blue74; 10-11-2019 at 03:32 PM. Reason: Added information.
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  2. #2
    Join Date
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    This is a photos of the breaker box I'm using in the garage with the other wiring removed. The blue cord is to pull the wires.
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  3. #3
    Join Date
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    I see the problem...The instructions for the breaker box are in Spanish...You'll need to hire a Hispanic electrician to make it work......Ben
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  4. #4
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    https://www.electricallicenserenewal...ectionID=505.0

    Best picture I found to show what you need. Since you are not using a metal raceway but PVC you will need a ground. It would tie to the right side of the main panel and to the lower grounding bar at the bottom of the right side panel.

    From the table here you can see the "MaX" capacity of your wire depending on the type of wire you are using.

    https://www.cerrowire.com/products/r...pacity-charts/

    Lastly you will need to ground your garage panel and also the "metal building" if you are placing it in there. That gets grounded to the upper right grounding bar.

    Since temps play a part I would safely stick to 40 amps or less. That's my story and I'm sticking to it.
    Fred

    "Everyday I beat my own previous record for number of consecutive days I've
    stayed alive."

    'Take care of yourself, and each other.'

  5. #5
    Join Date
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    Quote Originally Posted by FredK View Post
    https://www.electricallicenserenewal...ectionID=505.0

    Best picture I found to show what you need. Since you are not using a metal raceway but PVC you will need a ground. It would tie to the right side of the main panel and to the lower grounding bar at the bottom of the right side panel.

    From the table here you can see the "MaX" capacity of your wire depending on the type of wire you are using.

    https://www.cerrowire.com/products/r...pacity-charts/

    Lastly you will need to ground your garage panel and also the "metal building" if you are placing it in there. That gets grounded to the upper right grounding bar.

    Since temps play a part I would safely stick to 40 amps or less. That's my story and I'm sticking to it.
    The run is between 60 and 65 feet so I moved up from 10 ga to 8ga. Each circuit will be 30 amps.

    From looking at the diagram you posted and the breaker box I'm using. It looks like I need a ground bar in the box. And it looks like I will need 7 connections, one for the ground coming from the Cutoff Box, two for the wires from the ground rods and four for the ground from the circuits.
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    **************************************************
    Retired April 17, 2019
    Back to driving October 12, 2022
    Damn Credit Card
    Life’s too short to drink cheep booze and argue with stupid people.” Mickey Thompson

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