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Old 07-12-2011, 02:35 PM   #1
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Grounding/Replacing a Garage Sub Panel


I have a detached garage powered by a enclosed safety switch that comes underground from the house. It has never been grounded. This line to the garage basically powers 4 outlets and a automatic garage door . It's a 30 amp panel, probably 20-30 years old and contains two 2 -20 amp glass fuses. I'm never going to power anything "heavy duty" out there and I'm not interested in upgrading, except for safety. My main concern is the grounding issue and I know this has to addressed immediately.

I have two questions:

1) Should I replace this old switch with an updated model and if so which one?

2) How do I ground this old panel if I decide to keep it?

Thanks for the help.

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Old 07-12-2011, 04:10 PM   #2
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Grounding/Replacing a Garage Sub Panel


What is feeding this garage? Is it fed with a cable or wires through conduit?

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Old 07-12-2011, 07:50 PM   #3
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Originally Posted by a7ecorsair View Post
What is feeding this garage? Is it fed with a cable or wires through conduit?
Wires through a conduit.
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Old 07-12-2011, 08:50 PM   #4
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How do you know it’s not grounded? Did you use a meter to check?

If the conduit that feeds the panel is metal, and complete back to the main panel, that would be your ground.
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Old 07-12-2011, 09:20 PM   #5
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I got a shock when I touched the garage door rail when I'm not wearing shoes. I assume it's not grounded.
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Old 07-12-2011, 09:29 PM   #6
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Grounding/Replacing a Garage Sub Panel


You can’t just assume it is or isn’t grounded. You have to do some checks with a meter and verify. The panel may very well be grounded, but you may have a ground fault, something wired incorrectly, or another problem that is causing the issue.

How long has this been happening? Have you done any changes to the electrical lately? Do you have a meter?

Also, you didn’t answer the question if the conduit is metal and complete to the main panel.
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Old 07-12-2011, 09:55 PM   #7
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Grounding/Replacing a Garage Sub Panel


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I got a shock when I touched the garage door rail when I'm not wearing shoes. I assume it's not grounded.
What is the "garage door rail" - the track? Is it a roll up door or a swing up door? Does the garage door have an electric opener? Is it a metal garage door?
Your problem is not that the panel may not be grounded, but that you have leakage from some power source to the door or door track. Garage doors are typically supported by wood framing so the track could be hot and not affect anything until your grounded body touches it.
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Old 07-13-2011, 06:39 PM   #8
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Yes, it's metal with a roll up garage door with opener.
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Old 07-13-2011, 06:55 PM   #9
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Grounding/Replacing a Garage Sub Panel


First thing is to do a visual inspection of all parts of the door and track. Is the garage finished so you can see if there is any wiring anywhere close to the track hardware?
Do you have a volt meter? You will need some way to check for voltage without using your bare feet for the ground and you finger as a probe.
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Old 07-14-2011, 04:54 PM   #10
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I did a visual inspection of the track and the only things close are the:

*wiring for automatic sensor on both sides
*conduit wiring from panel to new motion light mounted on the corner of garage.
*Garage door unit is plugged into a 2 receptacle which is mounted on a beam which then travel 3' to a 4 receptacle outlet then continues to travel 15' along beam down to another receptacle which then travels straight back to the panel. On the other side of this same beam, another piece of BX runs back towards the garage door opener to a light receptacle (doesn't work). All of this wiring is BX.


I also determined that the cable that enters the garage (underground) comes off of one of my 20 amp services in the main box (listed as A/C in the panel) traveling about 50'. It enters the garage off one corner and is in conduit. There are three other conduit tube entrances, (one is capped, the other has nothing coming out of it and one is described by the following: "12/2 W Ground Type NM 600 v A.I.M. Amerflex". This wire leads directly to the sub panel.

Last edited by wmjp; 07-14-2011 at 05:01 PM.
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Old 07-14-2011, 05:02 PM   #11
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Still working on the volt meter!!

Last edited by wmjp; 07-14-2011 at 05:09 PM. Reason: copy of previous reply
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Old 07-14-2011, 05:05 PM   #12
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Last edited by wmjp; 07-14-2011 at 05:08 PM. Reason: Copy of same reply
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Old 07-15-2011, 11:12 AM   #13
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Grounding/Replacing a Garage Sub Panel


The type NM cable cannot be used in an underground appliacation.

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