# Grounding Rod In Detached Garage



## matt151617 (Jun 26, 2011)

First off, why are they required when there's still a ground going back to the main panel? My detached garage subpanel doesn't have a ground rod, only the ground going back to the main. Is there a good reason to add a rod?

Now, if I should add one, what would be the easiest way? The first pic shows the subpanel on the left. Getting outside the garage would require going over the top of the door, then out the side, under a deck, then into the ground. As shown in the second pic, behind the panel there's asphalt over cement, so there's no way to cut across there.


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## rrolleston (Oct 17, 2011)

Is this panel being fed with four wires? You could have the ground rods on any side of the garage. I have put ground rods through pavement before and you could also remove some decking boards and put the grounds under there.


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## Ravenworks (Oct 31, 2010)

I am sure someone will be along to answer your question with an answer,but something I always wondered is why you can't just go through the floor.As in either drill a one inch hole and hammer drill the GR in or sleeve GR in PVC?


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## rrolleston (Oct 17, 2011)

Ravenworks said:


> I am sure someone will be along to answer your question with an answer,but something I always wondered is why you can't just go through the floor.As in either drill a one inch hole and hammer drill the GR in or sleeve GR in PVC?


I have done that in a basement before in an old home made two over sized holes and put the rods in. Nicer if you can hide them outside though. You can't put the close to the edge of the slab because of the footing unless you have a really long drill bit.


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## joecaption (Nov 30, 2011)

It needs two ground rods not one and at least 6' apart.


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## AHJ (Mar 8, 2012)

The easiest way would be to drill a hole in the side walk. Go out of the building directly under the sub panel. Or you can order the wire to go around the building. Both ways would take probably the same amount of time. Or drill the hole inside the garage under the panel, this would depend on how the footings are done don't want to drill a three foot hole just to reach soil.


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## zappa (Nov 25, 2011)

Ravenworks said:


> I am sure someone will be along to answer your question with an answer,but something I always wondered is why you can't just go through the floor.As in either drill a one inch hole and hammer drill the GR in or sleeve GR in PVC?


Interesting story....We did just what you described in my test lab for an instrument that measures noise and signals feeding back into the power grid. A few years later I happened to noticed a creative brown tunnel built on the side of the 6" of rod that was above the floor level.

Termites!  The drilled hole was barely larger than the rod and I think some hydraulic cement or some kind of sealer would have stopped them but we didn't think about it at the time.


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## AllanJ (Nov 24, 2007)

The detached building with subpanel needs one 8' ground rod, connected to the subpanel with #6 copper. Plus the equipment grounding conductor (ground wire) accompanying and sized for the feed wires. Depending on the size of the feed wires this EGC may be smaller than #6 for exampe #10 for 30 to 60 amp feed.

The presence of a ground rod at the detached building does not reduce the need for two ground rods at the main building.

Running the grounding electrode conductor (for the ground rod) up and over the door and then out a hole in the wall should be no big deal.


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## Ravenworks (Oct 31, 2010)

Is there anything in the code prohibiting installing GR inside through the slab.


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## matt151617 (Jun 26, 2011)

Is the ground rod at the garage a safety issue? I understand it's required by code, but if it won't make any difference to the safety of the building, I'm not going to worry about it (no one is inspecting it or anything). The cost of 2 ground rods, connectors, and 40 feet or so of copper wire isn't cheap.


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## Anti-wingnut (Oct 18, 2009)

matt151617 said:


> Is the ground rod at the garage a safety issue? I understand it's required by code, but if it won't make any difference to the safety of the building, I'm not going to worry about it


Almost all codes, where ADA and energy conservation are clearly not the primary aim, are based on fire, life, seismic and storm safety.

Most of these items are not intrinsically safe or dangerous just by themselves. It takes the failure of more than one item to cause a problem. So the addition of a ground rod probably will not make your garage intrinsically safer. But it could interrupt a cascade of failures which could result in a dangerous situation.

The choice is yours


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## jbfan (Jul 1, 2004)

Grounds rods at a detached building are used to shunt lighting away from the ground path back to the main panel( in theory) anyway.


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## Missouri Bound (Apr 9, 2011)

Ravenworks said:


> I am sure someone will be along to answer your question with an answer,but something I always wondered is why you can't just go through the floor.As in either drill a one inch hole and hammer drill the GR in or sleeve GR in PVC?


 You certainly can install a ground rod inside the building, through the floor...ground is ground.


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## AllanJ (Nov 24, 2007)

One minor disadvantage of trying to drive the ground rod inside is this. If you hit a rock and the ground rod doesn't go down then you need to drill another hole in the floor to try again. Whereas if you do it outside you can simply move over a foot or so and try again.

Also it might be hard to start driving an 8 foot rod in a 7 foot high basement.


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## Missouri Bound (Apr 9, 2011)

AllanJ said:


> One minor disadvantage of trying to drive the ground rod inside is this. If you hit a rock and the ground rod doesn't go down then you need to drill another hole in the floor to try again. Whereas if you do it outside you can simply move over a foot or so and try again.
> 
> Also it might be hard to start driving an 8 foot rod in a 7 foot high basement.


 Other than the height issue, (you could bend it a bit) I witnessed a co-worker of mine do it with a pair of "sacrificial" vice grips. He just clamped them on the rod and beat it with a hammer until he could use his hammer drill.


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## md2lgyk (Jan 6, 2009)

joecaption said:


> It needs two ground rods not one and at least 6' apart.


Code does NOT require two ground rods. Common misconception. Two are usually used because that's cheaper than buying the expensive equipment necessary to verify that the resistance to ground of one rod is low enough.


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## brgmgb (Aug 25, 2011)

matt151617 said:


> Is the ground rod at the garage a safety issue? I understand it's required by code, but if it won't make any difference to the safety of the building, I'm not going to worry about it (no one is inspecting it or anything). The cost of 2 ground rods, connectors, and 40 feet or so of copper wire isn't cheap.


I installed the ground rods at my pole barn two weeks ago. The ground rods (5/8") were about $11.50 each. The #6 wire was about $1.50 per foot.


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## rrolleston (Oct 17, 2011)

I would check local supply houses I paid 95 cents a foot for #4 bare and they have #6 bare for about 50 cents a foot. Big box stores are usually overpriced.


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## brgmgb (Aug 25, 2011)

brgmgb said:


> I installed the ground rods at my pole barn two weeks ago. The ground rods (5/8") were about $11.50 each. The #6 wire was about $1.50 per foot.


I returned some leftover items and found the receipt from Menards. 5/8" ground rod was $11.47, the clamp was $2.87, and the 6-gauge stranded wire was $1.19 per foot.


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## rrolleston (Oct 17, 2011)

brgmgb said:


> I returned some leftover items and found the receipt from Menards. 5/8" ground rod was $11.47, the clamp was $2.87, and the 6-gauge stranded wire was $1.19 per foot.


WOW that's more than twice what I would pay around here. Hope that's for a copper coated rod.


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## AllanJ (Nov 24, 2007)

Did you really need 40' of wire to get from the subpanel to where you put the ground rod? The outbuilding ground rod does not need a direct #6 wire to the main building ground rods.


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## matt151617 (Jun 26, 2011)

More or less, yes, 40 feet. I have to go from the panel, up over the door, back down, then along the side of the building another 8 feet or so. Then through the wall, under the deck, out about 8 feet to the first ground rod, then 6 feet over to the next ground rod.

I have a bunch of #10 THHN, can I use that?

Also, around here, a copper-coated ground rod is $11.57, a couple dollars cheaper for galvanized steel. 25 feet of solid core copper wire is $29.54 for #4 and $22.66 for #6.


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## Daniel Holzman (Mar 10, 2009)

I have been puzzled for some time about the reason for the code requirements on grounding. I did some research, and not surprising the code requirements on electrical installations have gotten much more restrictive over the past 25 years or so, but NEC rarely discusses the reason for the changes.

For example, in the 1950's and even into the early 1960's houses did not typically have independent equipment grounds, outlets were two wire, and the neutral carried fault current as well as return current. There were no arc fault breakers, there were no GFI's. Grounding at the main panel was typically done with a single rod so far as I understand. Houses occasionally burned down due to electrical fault; whether they burned down more frequently than they do today, I cannot say.

Curiously, some of the old techniques persist. For example, dryers with old style combined neutral/ground are still permitted, similarly for ranges, provided it is a pre-existing condition. Pull chain lights typically lack an independent equipment ground, in fact I think porcelain screw in light fixtures are quite dangerous because of the potential for an exposed hot electrode.

The power company appears to be exempt from NEC rules, typically they do not have an independent equipment ground on their equipment, they ground through the neutral. Why it is that Joe homeowner needs an independent equipment ground but not the power company is somewhat mysterious to me.

So on to the outbuildings. Prior to independent equipment grounding, outbuildings likely would not have had ground rods. They would have been grounded using the neutral, like everything else. I don't know which edition of NEC required and independent equipment ground, but I will take a guess that the IEG rule came before NEC decided you needed a separate grounding system for detached outbuildings, but NOT for attached buildings. I presume the reason is that you could lose the IEG between the outbuilding and the house, and NEC wants a redundant system. As has been pointed out on this forum many times, you don't need a grounding system at all to operate equipment, the ground is only there for fault conditions such as lightning. So I don't know why the folks at NEC decided you needed a secondary grounding system for detached outbuildings but not for attached buildings like a garage, it certainly does not seem like it is a critical safety issue, but perhaps Stubbie can explain why the rule, and exactly what electrical peril you are going to be protected against.


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## shockme123 (Mar 8, 2012)

*ground rod*

hey man just drill your hole through you floor at a angle , in rocky ground that is mentioned in the NEC . all good


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## AllanJ (Nov 24, 2007)

his is not the reason for separate ground and neutral but, if the frame of equipment is connected to neutral, either because of a bootleg connection or a fault between neutral and ground, then the voltage at the frame relative to the earth can become non-zero producing a shock hazard since the bonding to the nearest grounding electrode is now current carrying.

So called double insulated tools can have a two prong plug and the chance of a fault from the tool body or frame to either hot or neutral is greatly reduced.

No inexperienced person is going to touch the combination neutral/ground/messenger wire (it's current carrying) between the house and the utility pole or touch anything that is connected/bonded/faulted to that wire and not also bonded to a ground rod or other grounding electrode via a means (not current conducting) other than that combination wire itself.


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## ddawg16 (Aug 15, 2011)

md2lgyk said:


> Code does NOT require two ground rods. Common misconception. Two are usually used because that's cheaper than buying the expensive equipment necessary to verify that the resistance to ground of one rod is low enough.


Correct. If you can confirm the ground resistance...one rod is fine....but most people don't have a megger to do the test....so it's quicker and eaiser to install the second rod.



Daniel Holzman said:


> I have been puzzled for some time about the reason for the code requirements on grounding. I did some research, and not surprising the code requirements on electrical installations have gotten much more restrictive over the past 25 years or so, but NEC rarely discusses the reason for the changes.
> 
> For example, in the 1950's and even into the early 1960's houses did not typically have independent equipment grounds, outlets were two wire, and the neutral carried fault current as well as return current. There were no arc fault breakers, there were no GFI's. Grounding at the main panel was typically done with a single rod so far as I understand. Houses occasionally burned down due to electrical fault; whether they burned down more frequently than they do today, I cannot say.
> 
> ...


Good background info....thanks for sharing.

As you essentually pointed out, grounding has been an evolving technology. In the old days, about the most sensitive electronic device in the house was an old tube radio that just about tolerate a direct lightning strike. With newer more sensitive equipement, grounding is becoming more of an issue...and we are learning more about safety issues...hence, GFI and AFIC.

Also note the trend towards using Ufer grounds....discovered before WWII, the benifits of them were not real obvious until recently.

Side note to the OP....make sure you do NOT bond the earth ground to the neutral buss in the sub panel....the only connection between neut and ground is at your main panel.

One more side note...on my 2-story addition...I have both an Ufer ground and 2 ground rods...and my plumbing ground....and....while I'm not required to do AFIC in the existing bedrooms....I will be....safety is kind of high on my list...especially with my kids....


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## rrolleston (Oct 17, 2011)

matt151617 said:


> More or less, yes, 40 feet. I have to go from the panel, up over the door, back down, then along the side of the building another 8 feet or so. Then through the wall, under the deck, out about 8 feet to the first ground rod, then 6 feet over to the next ground rod.
> 
> I have a bunch of #10 THHN, can I use that?
> 
> Also, around here, a copper-coated ground rod is $11.57, a couple dollars cheaper for galvanized steel. 25 feet of solid core copper wire is $29.54 for #4 and $22.66 for #6.


You are around my area if you ever have a big order of supplies you should check out http://www.dale-electric.com/.

#4 solid green .83 #6 solid green .53

They have really great prices that pretty much beat everyone else.


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## Stubbie (Jan 7, 2007)

Daniel Holzman said:


> I have been puzzled for some time about the reason for the code requirements on grounding. I did some research, and not surprising the code requirements on electrical installations have gotten much more restrictive over the past 25 years or so, but NEC rarely discusses the reason for the changes.
> 
> For example, in the 1950's and even into the early 1960's houses did not typically have independent equipment grounds, outlets were two wire, and the neutral carried fault current as well as return current. There were no arc fault breakers, there were no GFI's. Grounding at the main panel was typically done with a single rod so far as I understand. Houses occasionally burned down due to electrical fault; whether they burned down more frequently than they do today, I cannot say.
> 
> ...


Dan

The rule is 250.32 and subsequent subsections. Grounding systems as you have stated have been an evolving process. To address everything would take a long time. So I'll try to touch on some of the important issues for detached buildings. First you need a feeder not a branch circuit (15 or 20 amp) to the detached residential building to require an earth grounding system. 3 wire feeders to detached buildings were the norm for many years as were ground rods or some kind of earth electrode. In 2008 the 3 wire feeder was moved to existing only and 4 wire feeder with neutral and ground seperated at the detached structures panel the new mandate. This eliminates any possibility (hopefully) of added conductive parallel paths for neutral current. This of course had the byproduct of using a separate egc for facilitating the opening of overcurrent devices.

As for the earth grounding ie ground rods or other electrodes at the detached structure one of the misconceptions is that earth is at zero potential everywhere. As you know it is not and floats with resistance varying from point to point. Earth grounding is about controlling resistance to bring everthing in the electrical rim of the property to a controlled and hopefully same voltage potential. This is taken to the extreme in agriculutural buildings where equipotential grids are often imployed to eliminate even the slightest voltage potentials. And of course the earthing grounding provides for property protection against lighting and a few others I'm sure you are aware of from your research. So both egc and ges are really kind of partners in bonding to control high resistances that are detrimental to human safety and property in the event of any sort of electrical fault or such events as power surges and lightning, static etc.

I've kept a very good article in my files for quite some time which I think you will find interesting. It's rather long but I think it will answer the majority of your questions.

http://www.pfeiffereng.com/Principals%20of%20Electrical%20Grounding.pdf

Power companies use NESC rules and pretty much go under the assumption that their stuff is touched by authorized personnel only ... because they most certainly have their issues with system design that is less than desirable.

BTW.. I'm on a new computer system after my old computer died a slow death. Anyway my new email is not matching what I originally used so I could retrieve my password. so I'm now stubie and not stubbie.


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## zappa (Nov 25, 2011)

stubie said:


> BTW.. I'm on a new computer system after my old computer died a slow death. Anyway my new email is not matching what I originally used so I could retrieve my password. so I'm now stubie and not stubbie.


Dude...I thought you got banned er something!!! :laughing:


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## Stubbie (Jan 7, 2007)

zappa said:


> Dude...I thought you got banned er something!!! :laughing:


It's probably a miracle that I have not been after all these years and a bit of poor judgement from time to time....

I'm not sure what I used for my password as it just remembered when I brought up the forum. It was a while ago and I can't seem to dig it out of my memory banks. Anyway it was just easier to register again.


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## zappa (Nov 25, 2011)

Naaa, you are one of the most laid back posters on here. :thumbup:

I did think for a moment that someone was trying to impersonate you but the writing fit your style.

So is it stu-bee now? :jester: Ask the mods to get your name back!


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## a7ecorsair (Jun 1, 2010)

stubie said:


> BTW.. I'm on a new computer system after my old computer died a slow death. Anyway my new email is not matching what I originally used so I could retrieve my password. so I'm now stubie and not stubbie.


I knew there had to be a simple explanation. I suppose you lost the Ford avatar too. :whistling2:


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