Sharring ground rods

[Learning Always]

Running a new service to a detached garage from a meter that is mounted on the house 20ft away. The service at the house has been updated and has a water bond and 2 ground rods. Given the garage is so close to the house is there any reason not to run a gec from the garage to the house ground rods instead of driving 2 new rods at the garage? (10 ft more bare #6 outwieghs 2 rods and the labor to install at the garage.) I've looked through previous threads and 250 but dont see anything prohibiting it. Curious how others would handle the situation.

 

[texie]

I don't see any code issue. Some would argue that it is better. Normally all grounding electrodes in a building must be used and bonded together but sense these are 2 buildings it would not be required.

 

[don_resqcapt19]

The language in 250.32(A) is not completely clear as to the location of the second building grounding electrode system. I doubt that all AHJs would permit the one 20' away to be used for the second building grounding electrode system.
You should check with YOUR AHJ before doing the work.

 

[kwired]

How about one close to each building and one about dead center between them and a continuous length of conductor hitting each rod and equipment at each end of the run?

Gives EGC at the second structure some redundancy as well. Or if all conductors are direct buried can possibly serve as both EGC and GEC.

 

[Dennis Alwon]

The language in 250.32(A) is not completely clear as to the location of the second building grounding electrode system. I doubt that all AHJs would permit the one 20' away to be used for the second building grounding electrode system.
You should check with YOUR AHJ before doing the work.

Don if it is legal to use the equipment grounding conductor as an grounding electrode conductor then how could an inspector turn it down. Of course the equipment grounding conductor would have to be sized properly and terminated correctly.

 

[don_resqcapt19]

Don if it is legal to use the equipment grounding conductor as an grounding electrode conductor then how could an inspector turn it down. Of course the equipment grounding conductor would have to be sized properly and terminated correctly.

The code section implies, but stops short of saying, that the second building grounding electrode must be at the second building.

 

[texie]

I would allow the OP do do this without a second thought.

 

[kwired]

If you had a metallic water pipe run between the two buildings, you would have to connect to it at both ends and sort of end up having about same situation.

 

[Dennis Alwon]

The code section implies, but stops short of saying, that the second building grounding electrode must be at the second building.

Then that would negate the section about using the equipment grounding conductor as a grounding electrode conductor 250.121

250.121 Use of Equipment Grounding Conductors. An equip
ment
grounding conductor shall not be used as a grounding
electrode conductor.
Exception: A wire-type equipment grounding conductor installed in
compliance with 250.6(A) and the applicable requirements for both the
equipment grounding conductor and the grounding electrode conductor
in Parts II, III, and VI of this article shall be permitted to serve as both
an equipment grounding conductor and a grounding electrode conduc
tor.

 

[Dennis Alwon]

IMO, I think the grounding electrode conductor should be as short as possible so I would not use the rods at the house. I think it is a mistake to allow the equipment grounding conductor as a grounding electrode conductor also. Heck you could be hundreds of feet away

 

[roger]

If the GEC is bare copper in the earth I could see it as being an electrode itself on the way to the rods.

Roger

 

[kwired]

IMO, I think the grounding electrode conductor should be as short as possible so I would not use the rods at the house. I think it is a mistake to allow the equipment grounding conductor as a grounding electrode conductor also. Heck you could be hundreds of feet away

Hundreds of feet away is a different situation. 20 feet or less, you are at or near overlapping the "sphere of influence" of the rods if you placed them between the two structures, for this reason I'd go with like I said earlier and just three rods and solid conductor between both ends and hit each rod. Would not overlap the sphere of influence like you would if you went with four rods - two at each building, but 8 feet from the first puts you only maybe four feet between the middle two.

 

[Dennis Alwon]

Hundreds of feet away is a different situation. 20 feet or less, you are at or near overlapping the "sphere of influence" of the rods if you placed them between the two structures, for this reason I'd go with like I said earlier and just three rods and solid conductor between both ends and hit each rod. Would not overlap the sphere of influence like you would if you went with four rods - two at each building, but 8 feet from the first puts you only maybe four feet between the middle two.

So who makes that decision if it is too far or not. You are not always on the job so I can't rely on your call. hahahaha

Seriously, there is no distance mentioned in the NEC

 

[kwired]

If the GEC is bare copper in the earth I could see it as being an electrode itself on the way to the rods.

Roger

It maybe has some effectiveness but in itself is not a qualifying electrode per 250.52

 

[kwired]

So who makes that decision if it is too far or not. You are not always on the job so I can't rely on your call. hahahaha

Seriously, there is no distance mentioned in the NEC

Seriously, NEC makes a bigger deal out of grounding electrodes than they need to, and inspectors often seem to be indoctrinated, I mean certified, in places that manufacture ground rods.

 

[roger]

It maybe has some effectiveness but in itself is not a qualifying electrode per 250.52

Of course it doesn't qualify, did you think it might have?

Roger

 

[mbrooke]

It maybe has some effectiveness but in itself is not a qualifying electrode per 250.52

code does allow wire type electrodes

 

[don_resqcapt19]

Then that would negate the section about using the equipment grounding conductor as a grounding electrode conductor 250.121

Not really, the only application I see for that permission is for an SDS in the same building as the service equipment.

 

[mbrooke]

Seriously, NEC makes a bigger deal out of grounding electrodes than they need to, and inspectors often seem to be indoctrinated, I mean certified, in places that manufacture ground rods.

60 years ago the CMPs believe grounding electrodes were essential to fault clearing and system stability.

 

[don_resqcapt19]

So who makes that decision if it is too far or not. You are not always on the job so I can't rely on your call. hahahaha

Seriously, there is no distance mentioned in the NEC

Correct, there is no distance give in the NEC, so it is based on what your AHJ thinks "at" means.

250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)⁠(8) shall be instal⁠led and used.