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Old 04-03-2012, 03:06 PM   #1
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Alabama Sub Panel


Hello I have a few questions about Sub panel wiring.

I purchase a home here in Alabama that is about 2 years old. That has an external garage about 35 ft away with a sub panel service from the main house.

The current area I live in says that they use 2005 NEC Code standards and the house and garage were permited and passed code when built.

The wires connecting the sub panel runs from the main breaker box (50 amp breaker) through the house to an "outside disconnect" attached to the home about 50ft total from the main to the disconnect using Romex NM-B #6 awg 3 wire w/ground (ground is 10 awg). From the Disconnect it runs individual #6 THWN/THHN (Hot Hot Neu) and #10 THWN/THHN ground through PVC conduit to the detached garage sub panel. The ground and Neutral are not bonded at the sub panel only at the main like it should be.

Here are my concerns:

There does not seems to be a seperate ground rod for the detached garage, I am not sure if this was allowed in the 2005 NEC or not I am pretty sure it is required in the 2008 or newer. Was it required in the 2005 standard and/or should I install one?

If I do need to install a ground rod(s) should I install it at the disconnect attached to the house going to the sub (there is no main breaker in the sub panel the outside disconnect is its) or at the sub panel itself?

If I install the ground rod(s) I think I am suppose to use #6 awg bare or THWN wire to the sub panel ground. However doesn't that also mean with the current wiring that I would then have a second ground rod connected to the main house that is running through only the 10 awg ground sub feed wire almost 100 ft. Will this be an issue? Do I need to run a seperate #6 all the way back to the main breaker box to insure the main house does not have a second ground running through just a 10 awg wire and then code requires the ground be in the same channel so if I do need to run a #6 all the way back that would make the current Romex NM-B #6-3wG in the house invalid? Or is the #6 going to the sub plus the #10 feeding back to the main OK?

Thanks for any input

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Old 04-03-2012, 03:59 PM   #2
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Alabama Sub Panel


the current setup looks to be OK from the Main to the Sub panels.
i would think you need to add a grounding rod at the garage tho.
#6 with 10 ground is OK, so no need to re-run it.

add #6 copper-clad ground wire from the sub panel grounding bar to the rod/s and back again.

lets see what others have to say about this

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Old 04-03-2012, 04:12 PM   #3
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Last edited by jbfan; 04-04-2012 at 11:18 AM. Reason: wrong info!
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Old 04-04-2012, 08:38 AM   #4
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Thank you all for your help.
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Old 04-04-2012, 08:47 AM   #5
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Ground rods were not required at the garage in 05.
Was this a local thing?
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Old 04-04-2012, 10:38 AM   #6
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Ground rods were not required at the garage in 05.
My 2002 book states that a feeder run to a detached building with a separate grounding conductor requires a separate grounding electrode at the detached building. Did it change in '05?
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Old 04-04-2012, 11:04 AM   #7
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Grounding electrodes have been required at detached structures with feeders (regardless of type) for as long as I can remember.
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Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
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Old 04-04-2012, 11:09 AM   #8
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Grounding electrode at a detached garage with sub-panel has been required by the NEC since at least 1996 but as speedy said that requirement goes back over as many code cycles as I remember. I think JBfan may be thinking this was an attached garage.

Do not confuse your #10 awg ground in your feeder with the 'earth grounding' they are for two different puposes.

You simply need to add an 8' ground rod at the detached garage and make sure your neutral and grounding bars/terminal buses in the sub-panel are not bonded .. ie .. electrically connected. This is ususally accomplished by NOT installing the green screw or other bonding means.
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Old 04-04-2012, 11:18 AM   #9
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Again thanks for the input.

Like I said this house and garage was permitted and passed when it was built 2 years ago for the previous owner, and our code department still uses NEC 2005 not yet switched to 2008. I know in 2008 it was required to have both. (Part of this response was written before seeing some of the latest post but I left it the same)But if I remember correctly the 2005 NEC allowed one or the other, but I lost my 2005 book in the tornadoes last year. When it says “separate Ground conductor” in your 2002 does that mean that there is a separate ground wire from the main or does that mean that the ground conductor in the sub is separate from the main with no conductor between resulting in it requiring a rod? I guess I just need to get a copy again of the NEC 2005 if I can find it. Also, If 2005 allowed it was it permitted to have both or only one or the other since we still use 2005 here?

I would just put a rod in but I do not really want to get a permit for that simple of a thing plus when the previous builder buried the conduit he only put it about 4 inches underground then put a concrete drive on top and I do not want an inspector giving me heck for that when I just want to add a ground. Plus the concrete covers the area close to the sub panel so I would have to run a long #6 ground from a far side of the garage to connect it, and if I do it and don’t get a permit and some lookeey loo or inspector sees me driving in an 8 ft ground rod they will think I am up to no good.

Plus I know having an extra rod helps protect the structure from direct hits and less ohms to ground but if I remember right there can be the issues of ground loops and in rare cases of lightning (particularly lightning before the storm when ground is dry) close to either structure while the lighting is dispersing along the earth surface if it gets to one ground first it can actually run up one ground and out the other through your structures in its attempt to disperse (lot of theory in that one).

But I do thing that the pros out way any possible negatives on having one and NEC at least agrees in 2008 if not before. I just do not want to get a permit then possibly get one of those inspectors that turns out to be a jerk (Not all but there are some) involved or do it with out a permit and have one of those inspectors think I am doing no good and more than just an extra rod.
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Old 04-04-2012, 11:19 AM   #10
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Thanks guys.
I have no idea where that statement came from!

That is why we have such a great forum!
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Old 04-04-2012, 11:22 AM   #11
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Drive the rod and don't worry about a permit.
Drill a hole through the concrete next to the building.
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Old 04-04-2012, 12:56 PM   #12
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Again thanks for all the feed back.
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Old 04-05-2012, 10:15 AM   #13
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I guess I will be putting in one in the next week or two. I might as well get a second one to add to the house as well because they only have one rod on the home and I doubt they did 25 ohm testing to avoid the 2 rods. I guess the inspector in this area is not well grounded.... buudump ching.
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Old 04-07-2012, 03:45 PM   #14
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Originally Posted by KHman View Post
I guess I will be putting in one in the next week or two. I might as well get a second one to add to the house as well because they only have one rod on the home and I doubt they did 25 ohm testing to avoid the 2 rods. I guess the inspector in this area is not well grounded.... buudump ching.
Don't know where you are, but I'm in Huntsville and I have never seen them require two rods here.
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Old 04-10-2012, 10:35 AM   #15
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Alabama Sub Panel


Ground Rod installed this last weekend for the sub panel.

"Don't know where you are, but I'm in Huntsville and I have never seen them require two rods here. "

I am in Madison, it seems like I remember the NEC requiring either a 25 ohm test or two rods at least 8 ft apart they may not require it here and/or let is slide. Might be over kill but I may install the second one soon the rod is only like 12 bucks and I already have the wire. Plus right after I moved in last year a lightning hit close to the house killed two of my phones and a labtop power adapter.

Note as a possible tip: I got a 5/8th rod but I also bought a 3/8 long reach bit from Harbor Freight (One of those 4 ft bits that is made for drilling electic holes in wood that are hard to reach that cost like 5 bucks at HF with coupon but like 35 bucks at lowes/HD) I used the bit to pre drill the ground itself the first 4 ft (yes I know it sounds sill) which made it a lot better the first half so for 5 bucks I did not have to spend 10 minutes balancing on a ladder to hammer in the first 4 ft or use a large hammer drill plus the bit did not hit anything but clay so it still seems fine.

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