Ground Rod at Detached Structure

[infinity]

If the grounding electrode is a water pipe, the gec must be sized to 250.66 and a supplemental electrode must be installed (rod,pipe,plate) sized at #6.

If the ground electrode was a CEE it does not have to be larger then #4cu.

Would a CEE require a supplemental electrode?

If the electrode was building steel, the gec would be sized to 250.66.

Does building steel require a supplemental electrode?

Ground ring??? Not smaller than a #2. Again, would it need a supplemental?

SO? Water pipe is sized to entrance conductor size but would still need a supplemental?
Made supplementals not smaller than #6 and would need supplementals not smaller than #6?
The only "real" "non supplemental electrode would be metal frame of building structure and ground ring. Building structure would be sized to 250.66 and ring doesn't have to be larger than #2....and both would not
need a supplemental?

(reading on the ground ring..... not smaller than #2.......would that #2 be sized to go back to bond/ground, or would you have to hit the #2 with a gec sized to 250.66?)

Is any of what I wrote correct???

The only electrode that requires an additional supplemental electrode is the metallic water pipe electrode. No pipe then only one electrode is required.

 

[ritelec]

what a concept.............................

Would the #2 ground ring be sized for the gec at#2? Or would it be hit as per 250.66?

Thank you

 

[infinity]

what a concept.............................

Would the #2 ground ring be sized for the gec at#2? Or would it be hit as per 250.66?

Thank you

Good question.

250.66(C) Connections to Ground Rings. Where the grounding electrode conductor is connected to a ground ring as permitted in 250.52(A)(4), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than the conductor used for the ground ring.

 

[ritelec]

Thanks Rob

 

[don_resqcapt19]

Yes, but since no distance is specified, can I run a GEC from the garage to the house GES and comply?

That would be subjective. Talk to your AHJ.
The rule requires the electrode to be "at" the second structure. If there is more than a few feet between the two structures, I would not consider the electrode for the first structure to be "at" the second structure. Same way even if the two structures are separated by less than a few feet, the the electrode for the first structure is at the far side of that first structure.

 

[Cow]

Connecting the two GESs.

Huh?

I have ONE grounding electrode system being shared by two seperate structures.

 

[George Stolz]

It's a perfectly simple question:

Secondly, I've also installed a service feeding two seperate structures fairly close together, say 50' feet apart and drove rods between them. Ground wire from house---across two rods---and on to the detached building. One continuous wire and one grounding electrode system for two buildings.

Why would you interconnect the grounding electrode systems for the two separate buildings? It seems like a waste of time and money.

 

[Cow]

It's a perfectly simple question:



Why would you interconnect the grounding electrode systems for the two separate buildings? It seems like a waste of time and money.

I guess I'm just baffled why you think it takes extra time and money. I know my labor costs usually exceed the costs of materials for smaller jobs. So how do you suppose taking the extra time to drive a set of rods for each building is any cheaper than one set of rods with some #4 stretched out between two buildings?

I know I can reel off some extra #4 way faster than I can drive a second set of rods, it was an already open ditch, so why not?

 

[kwired]

I guess I'm just baffled why you think it takes extra time and money. I know my labor costs usually exceed the costs of materials for smaller jobs. So how do you suppose taking the extra time to drive a set of rods for each building is any cheaper than one set of rods with some #4 stretched out between two buildings?

I know I can reel off some extra #4 way faster than I can drive a second set of rods, it was an already open ditch, so why not?

Some of the sandy areas around here you can probably drive the rods faster than you can reel the wire off.


50 feet apart is about farthest apart I would consider doing this on. The labor to do it either way is probably not a big enough difference to break the entire budget of the project. You only put in the GES once and you are done with it. Not like you will have extra labor or materials for a task that is repeated hundreds of times

 

[George Stolz]

I guess I'm just baffled why you think it takes extra time and money.

1. Convincing inspector that the rods represent elements in the same GES, not two GESs that happen to be short a couple of rods and have an extraneous wire run between them - not that I wouldn't buy your argument, but would expect a tag before I would be presenting the argument.

2. Running the risk that the inspector will see the GEC and the EGC of the feeder as being a conductor in parallel not installed per 310.10(H)(5) - not that I would agree with that, but wouldn't be surprised at the tag.

3. 50' apart means probably 80' of #4 in your example, versus 30' of #6 among a pair of rods at each building.

4. The profound joy of wrestling a ground rod that might not cooperate fully in the bottom of a 4" wide 24" deep trench, trying to miss my feeder conductors...

5. The risk of inspector not seeing the rods at all, and failing for lack of them.

6. Much of which could be avoided by standing around waiting for the inspector, at added cost to the project.

Maybe I just have no sporting blood anymore.

 

[Dennis Alwon]

The cost of driving two extra rods at the second building outweighs the cost of the GEC between the buildings. I would prefer to drive the 2 extra rods but I don't think that Cow's way is more expensive at 50'.

 

[renosteinke]

I used to think that the matter of installing a panel in a detached garage was pretty straightforward. However, there have been various dicussions at this forum where various folks make a pretty good case that I haven't a clue.

What I have been doing is this:
4 wires to the panel in the detached building, sizing the ground (EGC) to match the ampacity of the feed, and a ground rod at the detached building, landing it's GEC at the panel in the detached building (IE: "garage")

The first objection focused on my using one ground rod. Oh, no, you need two. You can't consider the rod at the detached building as simply being another rod on the same grounding electrode system as the rod at the house- and how can you know if the resistance to ground will always be less than 25 ohms?

OK, so I bang in another rod.

The next objection was to my landing the GEC at the panel. Oh, No, you can't do that. The NEC specifically forbids that you use the ground wire of any feeder as part of the GEC.

Mind you, it wasn't long ago that folks commonly treated detachsed buildings as separate services, and didn't run any ground wire at all, as well as bonding the neutral at the garage panel. I've been 'ahead of my time' in running the green wire and keeping the ground and neutral separate .... but is seems I still don't know what I'm doing.

Yup. looks like we need not four, but five wires to the garage- with #5 being an unspliced EGC connecting the ground rods of the garage to the ground rods of the house. Look like the ground rods at the garage don't connect to the garage panel at all. At least (I think) the GEC does not have to be run together with the feeders. Whether I can run it through the air with an overhead feed is another debate .... now THERE's a magnet for copper thieves. Also keep in mind that the GEC can't be green.

Add to that local rules (like mine here) where they want the GEC to be #4, solid, AND in pipe, and things start getting interesting.

Now, maybe some day I'll find someone, somewhere, who has brought power to a detached building this way- multiple ground rods, extending the GEC from the house to the detached building, etc. Considering the number of detached buildings I've seen whose 'feeder' was a buried extension cord, I'm not expecting to see such an install anytime soon.

 

[ritelec]

Wow...............seams easier just to knock my garage down.

 

[George Stolz]

Wow...............seams easier just to knock my garage down.

Post of the day. :lol:

 

[don_resqcapt19]

...The next objection was to my landing the GEC at the panel. Oh, No, you can't do that. The NEC specifically forbids that you use the ground wire of any feeder as part of the GEC.

The fact the feeder EGC is rebonded to earth at the second building does not make the EGC a grounding electrode conductor. The code does not limit the number of times that you can connect an EGC to earth.

...Yup. looks like we need not four, but five wires to the garage- with #5 being an unspliced EGC connecting the ground rods of the garage to the ground rods of the house.

I see no reason for that in the code rules.

Look like the ground rods at the garage don't connect to the garage panel at all. At least (I think) the GEC does not have to be run together with the feeders.

The grounding electrode at the second building is required to be connected to the equipment grounding conductors at that second building. There is no requirement to "directly" connect the EGCs at the second building to the grounding electrode at the first building.

... Also keep in mind that the GEC can't be green. ...

The code does not say that the GEC cannot be green.

 

[Fulthrotl]

Wow...............seams easier just to knock my garage down.

i need my garage, so i disconnect it from the house service for safety,
then i just use a generator, drive six ground rods around it, and cadweld a 500mcm
around them in a pentagram.... cadwelding where the 500's cross of course.

then i put on a tinfoil hat so my thought waves can't be scanned, insulating the
tinfoil with a half lap layer of scotch 88 for shock protection, and start the generator.

if the generator won't start, i go looking for a small neighborhood creature to sacrifice
at the center of the pentagram, that always gets the generator running....

now, i don't actually use the electricity from the generator to power the building,
i feed the electricity into the photovoltaic cells on the roof, so they become a powerful
cloaking device similar to a romulan bird of prey.

once the generator is running, i then call for inspection... the cloaking device will make
the garage invisible to the inspector, and will drive the building inspector insane with frustration.

 

[John120/240]

Fulthrotl, I enjoy reading your response.

With a four wire feed to the garage, drive one ground rod. Seperate grounds and neutrals in

the sub panel. The fourth wire maintains ground continuity back to main panel. This is how

it is done here. Correct me if I am mistaken.

 

[kwired]

Fulthrotl, I enjoy reading your response.

With a four wire feed to the garage, drive one ground rod. Seperate grounds and neutrals in

the sub panel. The fourth wire maintains ground continuity back to main panel. This is how

it is done here. Correct me if I am mistaken.

Insert after "drive one ground rod" :If first rod is greater than 25 ohms drive a second rod, or just drive second rod if you can't accurately determine resistance of first rod.

The other way is to delete "drive one ground rod" and replace with "connect concrete encased electrode" if you have one of those to connect.

 

[ritelec]

if the generator won't start, i go looking for a small neighborhood creature to sacrifice
at the center of the pentagram, that always gets the generator running....

I watch them ghost shows.............watch out for that stuff.

NO KIDDING!!!

 

[Fulthrotl]

I watch them ghost shows.............watch out for that stuff.

NO KIDDING!!!

the best part is the inspector having to talk to a guy wearing a tinfoil hat requesting
an electrical inspection on a building he can't see.....

and realizing that this is what he went to college for four years to be qualified to do.

that's when he'll snap.