ECN Forum Forums Code Related Discussion NEC & other Code issues 05 equipotential bond.

Has anybody determined wether we are supposed to establish this bonding grid under a fiberglass pool?

680.26(C)(3)b. seems to imply this requirement.

There was a fiberglass pool company at the home show in Bawstin today, and he had not heard anything of this new bonding grid.He said they had installations currently in progress

shortcircuit

IMO
As the language appears in the Code at this moment, the grid would be required beneath a fiberglass pool.


Charlie

Wait for the TIA

Charlie

I bounced this off the IAEI guys and they say this only refers to 3' of the deck
"Follow the contour" refers to where the 3' starts in reference to the water's edge.

I read it that way too. Why do you need to bond the dirt under a non-conductive pool? Bonding 3' of the perimeter will do all you need

I'd like to think that the IAEI guys have it right but Others are not so sure. As I understand it there may be a TIA on the way, but obviously that is not official.

Ultimately if you read 680.26 (B) (1) the last couple of sentences state

"Where reinforcing steel of the pool shell or the reinforcing steel of coping stones and deck and deck is encapsulated with a nonconductive compound or other conductive material is not available, provisions shall be ,made for an alternative means to eliminate voltage gradients that would other wise be provided by un-encapsulated , bonded reinforcing steel."

The alternate means in 680.26(C) (3) (b)

States that "the equipotential bonding grid shall cover the contour of the pool and the pool deck "

This sentence undeniably states the grid shall follow the contour of the pool. I don't expect that to mean "like a tent" I interpret it to mean under the pool and follow the contour of the pool (hole).

The second part of the sentence specifically refers to the grin also under the deck and out 3 feet.

If it looks like a duck, walks like a duck and quacks like a duck. It's a Duck.

Charlie Palmieri

I think they are looking at "that would other wise be provided by un-encapsulated , bonded reinforcing steel"
There was never going to be any steel providing a grid in a plastic pool. Since the grid would be effectively insulated from the water by the pool I don't see any advantage of bonding dirt under the pool.
This is as dumb as bonding PVC pipe.
I do agree this is going to seriously impact, if not eliminate, fibermesh concrete decks and pavers but I don't think it will affect the hole under a glass pool.
As is true with most things the AHJ will decide but it looks like the Florida IAEI is being reasonable.
BTW do you think they would have to put the grid under a wood deck? That is certainly more conductive than a glass pool.

Previous to the 2005 NEC the Mass Electric Code recognized an issue regarding epoxy encapsulated re-bar in poured pools. This state required under such condition that a # 8 Solid Copper be ran through the re-bar at a distance of 15 feet. Comment 17-171 on Proposal 17-124 (680.27 ) originally suggested a 3 foot spacing this was submitted by a Mass Code Advisory Panel Member and was accepted in principle. The language that found it's way to the text as you know is 12". Also Proposal 17-120 (680.26(B) (6)) was accepted at the proposal stage and apparently rejected in comment # 17-167. This proposal specifically stated to bond the pool water. The panel accepted it 10 to 1.

The whole drift that I get from reading the proposals is that which was submitted in proposal 17-120. It was submitted by a representative of a power company citing gradient voltages from their system finding it's way into the pool water (Liability). “Ground Potential Rise”. The proposal discussed non conductive liners (not that much different from a fiber glass liner, do you own a glass hull boat?) preventing the pool water from coming in contact with the bonding grid. .

The fact is if you read the proposals and the comments it is difficult to determine where the CMP deviated from the original proposal when it spelled out the need to bond in 680.26 (B) and the alternate means described in 680.26 (C).
Personally I'm in NO BIG hurry to bond the pool water, but I do know that glass hulls of boats transmit and hold water (osmosis). I don't see the difference with a glass pool.
The NEC needs to make up it's mind. concerning these installations. The only body that can interpret the NEC is the Code Panel. The local jurisdictions (Gov’t Bodies) can amend the NEC as is done in Massachusetts.

The language in the book does not provide a great amount of wiggle room.

Charlie Palmieri

This is confusing ...but I'm sure we professionals can sort this out...

In the 2005 Analysis oc Changes from the IAEI on page 327 there is a picture of a pool with nonconductive reinforcing steel and the alternative method of establishing a grid is shown in the picture only under the 3 foot walking surface extending beyond the pools edge.

So maybe the concern is only for the paved walking surface around the pool where we would be in contact with those stray voltages.

But why only the PAVED surface. My cousin has a pool that has grass lawn up to within 1 foot of the water and then stone surrounding the pools edge. Would not these stray voltage gradients be present in the earths natural surface as also?

Also, this bonding of the pools water as you describe, this is acomplished through bonding of the pools wet niche or the metal hand rail for exsample. What if there is nothing associated with the pools water that needs bonding?

The fiberglass pool company that I saw at the home show in Bawstin said sometimes there is nothing to bond in direct contact with the water. For exsample they would use fiber optic lighting and there would be no other metalic parts in contact with the water requiring bonding.

In this case wouldn't there be a potential difference between the water and the EBG surrounding the pool?

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Shortcircuit
The illustration in the IAEI Book only indicates that it is useless to attach a bonding conductor to the coated reinforcing steel. The Paragraph on the same page “Analysis and Effect” middle of, states. It is not required etc. Further down it states that 680.26 (B) does not specify any particular method , but 680.26 (C) (3) does cover alternate means of establishing a grid.

I would not bet the ranch on the alternate means being limited to the 3 feet under the decking on that illustration.

Section 680.26 (C) requires the grid to extend under paved walking surfaces. Is the surface you refer to paved??

If not I do not see where the language of the Code addresses grass areas surrounding the pool. Agreed it is just as susceptible to voltage gradients as a paved surface.

I still think the NFPA has some work to do. If they do not keep and eye on the MEC it is my understanding that this issue will be addressed if the NEC does not do something but then again at this stage it is all talk.

Charlie

cpal...I'm just trying to understand the new EBG rules so I know how to apply them. I'm not currently involved with a pool installation.But there are swimming pools currently being installed in Mass that are subject to the 2005 MEC...maybe we need a interpretation from NFPA? IAEI?

Also, what do you think of the fiberglass swimming pool as I described in my last post with no metalic parts bonded that are in contact with the water in the pool? Is this cause for concern with fiberglass pools?

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