Garage Ground Rod Required


Old 05-17-05, 08:04 PM
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Question Garage Ground Rod Required

I keep getting very confused with my books and the internet sites on this one. HELP

Have/Will Have:
Detached Garage, no metal shared except for Feeder cable
65' of 10/3 UF-B Burried (My Feeder)
6 slot SD QO Sub Panel (Not bonded ground/common, no disconnect)
3 Circuit Breakers in the sub panel
Fed from the SE panel (ground/common bonded)
Disconnect is my SE panel's 30 amp breaker

Will this suffice for code, or do I need a second set of grounding rods beyond the main ones in my house's foundation?


[P.S. My father in law who is a retired electrician talked me into this while he is here visiting, he believes I don't need to drive new grounding rods, but I am nervous.]
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Old 05-17-05, 08:12 PM
Speedy Petey's Avatar
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Yes, you do need a ground rod at a detached structure with a panel.
According to code if you can't prove 25 ohms or less on the ground rod you need a second. This is an impossible test for a DIY and many electricians so two are usually used.
If your soil is not all sand I would safely say one is fine for such a small sub-feed.
Old 05-17-05, 08:20 PM
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Danke Petey, my soil is red clay from 3 inches. I didn't want to cause a problem w/ my wife family, so I'll drive it after he's headed back home tomorrow.

Any hints on getting one into clay? Galvinized or Copper? 6 Ft. deep--Ug? 6 gauge copper wire and acorn clamp?
Old 05-17-05, 08:23 PM
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Copper clad rod, 8' long, flush with the soil. #6cu to the rod. A lump hammer and some spinach. You will get Popeye foreamrs.

PS - How did you know I was German?
Old 05-18-05, 06:58 AM
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I suggest in Clay you run a hose over to the area where you are going to drive the rod and let the water run for about 35 minutes....sure it will only go down so far but when driving the rod the muddy area and moisture will add some lubrication to the driving process.....don't hear Speedy laughing already......we tested this and it was easier but again I had my helper do it...thehehehehe So it was VERY easy for me....
Old 05-18-05, 08:45 AM
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I'll give the soaking a shot, I don't swing the best heavy hammer, so I'll take any help I can get.

Will a 1/2" rod work, or should I go up to the next bigger size diameter (5/8"?)?

If I can't find a lump hammer, will an ordinary short handle sledge put me much at a disadvantage? Should I search far and wide for a lump hammer?

Thanks again,

Petey, I actually studied in Germany in grad school so sometimes it mixes in just to keep things interesting, I think my vocabulary now is about 30 words, 3 of them being curse words.

Last edited by Beeek; 05-18-05 at 09:43 AM.
Old 05-18-05, 01:23 PM
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When I hear this I always have a question about the wire and grouding/bonding. This is a 10/3 wire with ground? 4 wires in this cable?
Old 05-18-05, 01:44 PM
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Since you are running a four wire feed, you must not bond the common and the ground.
Old 05-18-05, 07:31 PM
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sberry & joed,
10/3 UF-B w/ ground. Thank you for checking. I threw away the bonding screw for the sub panel.

I left out that 4 wire part in my original description and can now appreciate your questions/comments. I have only worked with NM before, so I forget not all cable has a ground.

In my original post, I wanted to convey that only my SE was bonded common to ground. I wanted to make sure I .... we weren't messing that up.

I dug a skinny 1.5 ft hole to funnel my water and I fed my hole water for a while, and it (to my surprise) it took a decent amount. I guess I have more topsoil next to the garage then in the middle of the yard when they removed a sidewalk slab and clay was directly under it (i.e. 3 inches). The 8' rod went in well to about half way and then it moved just a couple 1/4s an inch with each hammer blow. So that is when I hit the clay, it was steady in, but slow. Not as bad as I thought with a 3lb drilling hammer from Lowes. Ended up only having 5/8" 8' copper clad.

Petey, I looked up lump hammer on the web (thanks), got a picture, so I knew what to look for when tool shopping.

I think I am ready for inspection.

Thanks AGAIN everyone for your time. It's not that I don't trust my father in law, um, I'll be quiet now...
Old 05-21-05, 06:30 AM
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Yeppers as their are different codes in response to "detached" and " attached" garages and all you need is a small breezeway connecting the house to the garage...and whola....." attached " and only needs a 4 wire sub panel from the main panel and no seperate ground rod needed...BUT if detached then you can run a 3 wire and drive your own rod.....cost wise it is cheaper in the " detached " code is code.

On driving the rod and the size....go with 5/8" and have you ever driven one using a post hole driver....we do all the time and works better than a sledge hammer as it seems my helpers ( and myself ) dont have the greatest aim and got tired of the broken handles from the helpers

The slip over post hole slammers work GREAT for driving rods.....give that a try sometime.....they fit over the rod and you slide it up and slam it down...we drove (2) rods in 30 minutes using one...

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