ECN Forum Forums Code Related Discussion NEC & other Code issues Equipotential Bonding Grid

Hey folks, it's been a few years since I have posted here. Hope to add more in the future.

Well it's been years since I wired a pool and one of my customers asked me to wire his new inground pool for him. Being studious as I am I started reading..

Well I am somewhat baffled by the Equipotential bonding grid. I see pics in Mike Holts book and it looks like a copper grid that all the bonding comes from or goes to. Not quite sure.

Can someone tell me what the blazes this is? who supplies it, things like that.

Thanks

Tom

You can make one or buy one. If it's in a cement slab, your local AHJ may still allow you to use the common reinforcing mesh.

Copper grids are made by Burndy. A simgle 50-ft x 36" roll will cost you about $700. Your electrical supplier can get you more information.

Thanks, but I still don't understand what to do with it if I were to buy one. The pool is cement with rebar sticking out every 5 feet or so.. I have never seen this before, like I said it's been years since I did a pool job.

What is its purpose?

OK, time for a little history here ...

(and I'll try not to garble it up this time! )

We used to make pools out of concrete, and our pipes were metal. No problems.

Then we started making our pools out of metal that was wrapped in plastic - effectively insulating the shell - and the pipes out of plastic. People started getting tingles when they sat on the deck and dangled their legs in the water. Amazingly enough, this problem only happened with the fresh water filled pools.

Wherever the electricity comes from, it was felt that the solution was to bond everything together to a ridiculous degree. Along cane this 'equipotential plane' and even a requirement to 'bond' the water.

Code requirements seesawed back and forth; I think the latest version has returned to specifying a copper grid, in preference to just ordinary rebar. I might be a bit off - perhaps the copper is only called for if there's no concrete deck. Apparently the copper wire that goes around the pool, bonding the shell in four places, isn't enough.

As for bonding the water ... if you don't have metal pipe to bond to, there are a variety of metal gizmos made to help you do this.

The entire purpose of all this is to make sure the ground around the pool is at the same exact potential as the water inside the pool.

In the 2008 code you are allowed to make one ring of #8 copper around the pool 18 - 24" from the edge of the pool but if you are putting rebar in the deck that works too. It needs to be connected in a minimum of 4 places evenly distributed around the pool to the pool shell steel. In 2005 that was required to be a 1 ft x 1 ft matrix of #8 copper but they backed off of that in 2008.

The regular steel wire mesh is not seen as compliant by a lot of AHJs since it says "structural steel" but they did remove the word "bars" so it could be a tossup.
The open question is, can you put in a #3 rebar ring cheaper than a #8 copper? I bet you can, simply because you don't need acorns connecting the rebar together (regular tie wire works) and you would need 4 acorns for the #8.

Thanks, thius pool is concrete, I see no mesh it looks like a building foundation of a house sort of.. It has rebar coming out near the top every 5 feet or so. It looks like the rebar will be the support for the concrete walk.. I'll be they are putting a mesh attaced to the rebar.. Ahhh that is what they must be thinking.. So asuming there is a wire mesh of steel attached to the rebar..

All I need to do is bond it four points?

You know, I don't even know what year code they are using.. Here in Long Island different towns use different code versions. They take years to adopt new codes.. LOL. In 2005 they mostly were still on the 99 code.. I think they mostly use the 2005 now but not sure. I need to figure that out first.

Electrical work died for me over the last few years so I lost count of what is going on.

Thanks man.

tsolanto,

As Reno said, the code seesawed back and forth, so it is very important to know which version of the code you have to follow. In one code you needed that 3 foot wide copper mesh ring, in another code, you just needed an single ring of #8 Cu.. This is one section of the NEC that always seems to get tweaked.

You could always use rebar so that is probably the cheapest solution since you already have the rods sticking out. That was the way they did my pool. I had rods sticking out from the bond beam around the pool and we ran a couple rings of #3 around the deck area.

in 2005 680.26(C)(1) said "Structural reinforcing steel ... bonded together by the usual steel tie wires".

I also stubbed out several #8s from the bonding grid to bond my screen cage and, later when I added on, I had a way to continue the bonding grid to the new deck.

2005 NEC

In Mass the copper mesh was repealed in'06.
Not sure if that was at the national level.

I never had a problem using the mesh or rebar installed by others. Just make sure that your bond ring hits every thing metal associated with the pool.

This is NOT a ground,it IS a bond.

Thanks everyone, well I just spoke to the adj and it's a #8 ring around the pool 2.5 feet from the water edge bond 4 points plus all the other metal parts, ladders and such.

Thanks a ton guys. Hope to be around more ...