Grounding question

[e57]

So I got a good one today, and failed the first inspection in who knows how long. (I cant remember the last...)

Here's the scenario: An addition to an existing house, with a seperate sub from a new main panel, mounted to a fence.
The feeder to the addition contains a full-sized (for the service) ground. But only done as an electrode for the building. I didn't see, or wasn't paying attention to a copper water line at the fence to the irrigation. But apparently there is water available at the fence.

As for the water line at a fence that the main panel is located on - No one knows if it is a branch of the main water, or a branch from the existing house to the irrigation. The Inspector wants it as an electrode to the MCOP.

So the question is, should it also be used as an electrode for the main panel?

 

[e57]

Before we go any further, my picture doesn't really do justice...

The existing structure is on one plot, and the addition is on another adjacent plot originally. They are only joined together as a single building by a bridge on the second floor. There are no water lines between them, or electrical EGC connections for that matter. Outside of the bridge they are seperate structures. Confused yet? I was...

There is a neutral bond in the main, and in the existing. Not in the addition, because I was unsure of parralel paths, I have no idea where the plumber got the water for the addition. Property #1 or #2?

 

[Smart $]

The requirement to bond to metal water line is regarding building or structure served. By Art. 100, the fence meets the definition of structure

 

[George Stolz]

Mark, I would say the differentiation of different/same structures falls under 90.4.

IMO, the bridge joins the structures. So, all the electrodes would be connected to the service disconnecting means, and there would be all EGC's after that.

IMO.

 

[George Stolz]

I have read closer.

Here's the scenario: An addition to an existing house, with a seperate sub from a new main panel, mounted to a fence.

I'd agree with the idea that the fence is a seperate structure. If that is the case, then the questionable electrode (questionably continuous) should apply to 250.32(B)(1), IMO.

So the question is, should it also be used as an electrode for the main panel?

I would say "no", the water pipe at the fence is an electrode present at the fence, not the originating structure.

 

[e57]

The fence is totaly seperate from the building +/or buildings. An electrode is definately required at both the fence, and the building(s). The question is how thay are connected? And the water at the fence? Seeing that both portions of the buildings have a bond/electrode to water this "hose bib" at/near the fence is already bonded in one way or another from either structure 35' away. Had I noticed it before, I would have given it more thought... Not even sure if the water is of the same water service. If it is, the neutral/ground bond in the existing structure will need to be removed to eliminated parralel paths for current between the existing building and MCOP.

Electrodes are required at each building, they do not share a common foundation. Both concrete floors on grade. The water, may be common?

Technically the electrodes in the existing and addition should be joined. Only because of the bridge. But not possible as you would have to seriously trench through the slab of the existing to get to it. And re-pulling conductors to the existing is also not possible as the conductors are pretty well siezed.

The fence is the originating structure for the electrical service. But the water (a branch water) already enjoys being an electrode at one, if not two places.

As for 90.4, I already got my answer... He'll be happy to add the hose bib to the main as an electrode, he did not even think about how the bonding jumper in the house is going to effect this.

Had there been no irrigation and hose bib there at the fence, I would be done.... But I didn't see it...

 

[George Stolz]

Can you draw a one-line of this? I'm not seeing the grounding connections. I'm assuming you don't have an EGC between the fence's service and the MDP inside the existing wing of the structi.

(Structi is what we shall call this beast. )

 

[e57]

Nope, no ECG between the fence and existing "structi". (?)

 

[e57]

Please click one of the Quick Reply icons in the posts above to activate Quick Reply.

 

[Dnkldorf]

Here are my questions:

I can't see how the AHJ can make you use that water at the fence as an electrode. Someone (probably you) would have to dig it up and make sure it is in contact to the earth for at least 10'. 250 allows us to use it as an electrode, if it meets this criteria. How does he know, or you, that 5' down it doesn't change over to a plastic pipe?

Bonding that pipe at the fence. How is it likely to be become energized?

 

[George Stolz]

"structi". (?)

Well, it's arguably not a structure, and not structures. So, let's make up our own word: Structi. That looks plural but isn't, since it's a made-up word. It works perfectly.

 

[George Stolz]

I can't see how the AHJ can make you use that water at the fence as an electrode. Someone (probably you) would have to dig it up and make sure it is in contact to the earth for at least 10'. 250 allows us to use it as an electrode, if it meets this criteria. How does he know, or you, that 5' down it doesn't change over to a plastic pipe?

There's nothing saying the inspector can't assume the pipe is continuous. I bet most inspectors in my area don't give the water pipe a second thought, as it's assumed to be copper out to the street.

Once the assumption is made, then the act of requiring is easy.

Bonding that pipe at the fence. How is it likely to be become energized?

250.104 would not require the pipe to be bonded if it did not qualify as a grounding electrode. The water pipe is not "installed in or attached to a building or structure". 250.50 states all electrodes present "at" a structure are to be used. I would say "at" is more inclusive than "installed in" or "attached to."

So, the effective result of the wording would be that if a water pipe is at a structure, and qualifies as a grounding electrode according to 250.52(A)(1), then it must be used.

If it doesn't qualify as a grounding electrode, 250.104 steps in to require bonding of some pipes. This pipe doesn't readily fall into that wording, so it could arguably be left unbonded.

Is that some serious code massaging or what!

 

[e57]

Is that some serious code massaging or what!

Could you work on my back?

As for the pipe, nobody knows much about it, as fr as wht its from or to, it could very well be plastic, as there is a bunch of illegal irrigation lines also in plastic there.

But the inspector has spoken..... FULL SIZED GEC! In pipe at that....

 

[George Stolz]

Mark, if I'm picturing this right, then I would say that the feeder between the fence and the building must have an EGC, if there is continuity between the sprinkler pipe and the building's water supply. 250.32(B)(2) stipulates no metallic paths bonded in both structures, and you'd have that.

I'd say even if the sprinkler was supplied from it's own street tap, this would still violate 250.32, the way it's worded.

A simple fix would be to remove the fence's water pipe electrode from qualifying as an electrode - install a piece of PVC in the water pipe so it's length is less than 10'. Problem solved.

 

[e57]

Oh I agree, installing a GEC to the sprinkler/hose bib would voilate 250.32, as then there would be parralel paths on the water in existing. The bonding jumper in the existing needs to come out, as I can not get the water in plastic. (Although some of it may be, the plumbing is all hack work.) Locally, PVC is illegal here for plumbing above or below grade. (PVC for electrical is illegal for any electrical above grade not encased.)