Equal Potential Plain

[ArcherC]

Hey Everyone,
I have not posted here often but something has come to my attention that might be of interest. If you have any information about this topic, please share.

I had a meeting yesterday with the electrician who hooks up most of our spas. During the course of the talk he asked me if we knew of the newest national code requiring an equal potential plain around all pools and spas. I said that this was something I had not heard of.

He went on to inform me that starting July 1st of this year, all pools and spas must be built with 3' of cement on all sides of the spa, set with rebar in a 12" grid and bonded to the spa.

So any spas delivered onto an existing concrete pad will be inspected and be made to be moved.  I am checking with the electrical inspector in our area to see how to overcome this new problem. When speaking with our electrician, he said that the only way he new of to still be legal and set the spa on the concrete pad was to build a short deck on it that extends 3 feet out on all sides from the spa, or to make a 12x12 pad out of plastic like Confer makes and lay it on the old cement.

Hopefully this is not as bad as it sounds and hopefully there will be provisions made for portable spas, but right now it is very troubling. Any comments or knowledge would be appreciated.

[BobRex]

I don't understand.  Concrete's not conductive; if properly placed, the rebar isn't grounded (assuming the 3-6 inches of stone between the rebar and earth proper) so if you "bonded" the rebar to the frame you could possibly create an insulated web (rebar) with a potential (sort of a giant capacitor.)  Umm, so what??

I see a potential hazard here if the rebar is exposed, say due to weather, and someone touched the rebar while standing on wet grass.  

Am I missing something?

[Drewski]

I'd like to see the code, not what "someone" says...

I might understand such a requirement for a "built in" unit, literally constructed like a pool. BUT, how can it be applied to a "portable appliance," ALREADY meeting it's own requirements? If grounding is the issue, why not require an independent "direct to dirt" ground in addition to a GFCI circuit?

I'm thinking decks are the answer...

Drewski

[Steve]

Sounds a little hokey to me.

[ArcherC]

It sounded odd to me as well. I will let you all know as soon as I see a copy of the code. But I really hope the electrician was pulling my leg. This kind of garbage can really turn people off to buying a product.

[johnvb]

First thing you need to do is contact your local inspection office and find out what code they are now using. Check their web-site if they have one.

In my area (Virginia Beach, Va.) they are still going by the 1996 NEC and the 2000 International Residential building code. So as of today, this new "rule" should not apply in my area.

[Chas]

One thing I do know: Concrete is very much conductive.

Take your meter out near your spa, put one lead on the hot lead going into your equipment and simply put the other one on the cement. You'll be amazed.

[Drewski]

Hmmm, just a thought:

Does this mean above ground pools will need to meet the same (assumed) requirement? If not, why not?

THAT could get expensive...

Drewski

[myke]

just ran across this..


http://ewweb.com/mag/electric_code_changes_11/

[BobRex]

Chas

Concrete is made of sand (a semiconductor) and lime plus an aggregate.  Now I work for a power company and just asked 2 different power EEs if concrete is conductive.  Both agree with me that, in and of itself, concrete is nonconductive.  BUT... it is possible that an iron based aggregate could pass a current, same as water in the concrete, and also maybe rebar close to the surface.  I'm going to meter a slab tonight, I'll report my findings.

I also read the code definition supplied by myke.  I see the word permanent used.  Since above ground spas are considered portable, I wonder if the NEC was thinking of "portable" spas when they developed this.

[Vinny]

Hmmm, just a thought:

Does this mean above ground pools will need to meet the same (assumed) requirement? If not, why not?

THAT could get expensive...

Drewski

Above ground pools usually aren't put onto concrete (I guess some are) and they are supposed to be bonded to the pump motor during installation.

[Drewski]

just ran across this..

http://ewweb.com/mag/electric_code_changes_11/

THANKS myke! Good source...

Key thing if you read it here guys, the code refers to "permanently installed pools, outdoor spas, and outdoor hot tubs."

Last time I checked, most of the stuff we have is considered "portable."

Drewski

[Brewman]

Also, NEC code changes are for installations going forward, once a locality has adopted that year's code.
So even if this applied to portable hot tubs, it would only apply to new installations in locations that were enforcing the 2005 code.
You would not be required to retro fit any existing applications.  


Brewman

[Dr. Spa™ Ret.]

THANKS myke! Good source...

Key thing if you read it here guys, the code refers to "permanently installed pools, outdoor spas, and outdoor hot tubs."

Last time I checked, most of the stuff we have is considered "portable."

Drewski

 

A matter of semantics, but since most codes can be slightly open to interpretation by inspectors;

" The following parts of a permanently installed pool, outdoor spa, and outdoor hot tub must be bonded to a equipotential bonding grid of the type specified in 680.26(C)."

The punctuation of the sentence indicates 3 separate things.

1. permanently installed pool
2. outdoor spa
3. outdoor hot tub

The word "permanently" is only associated with "pool", while "spa or hot tub" is not defined as either portable or permanently installed.

If there was a comma after the word "installed" ( permanently installed, pool), then it would indicate that all three vessels of water would have to be permanently installed to be effected by the requirement.

[windsurfdog]

Regarding concrete being a conductor of electricity (and a good conductor, at that) check out this incident.

In a previous life, I held a master electrician's license.  I was checking out the electrical system of a new house after power was initially turned on.  A carpenter was complaining of being shocked as he knelt on a p.t. wood deck and touching the brick on the house.  I measured over 100 volts A/C between the brick wall and the deck!  I traced the problem to the washer circuit....apparently a nail that was used to secure one of the metal tabs that the masons used to tie the bricks/mortar to the wood framing of the house penetrated the hot conductor of the romex cable without touching the neutral or the ground.  The resistance of the brick was enough to resist substantial current flow thereby causing the breaker not to trip.....the voltage was just sitting in the brick wall waiting to go to ground, which it did when the carpenter touched the wall while kneeling on the wood deck and the wood was new and still "wet" with pressure treated chems.  In testing this with a meter, the voltage would be the greatest at the closest point to the fault and would drop off as I tested the wall-to-deck further from the fault.  So I'd say all three--brick/mortar, new p.t. decking and concrete are pretty good conductors.

BTW, that was one of the most challenging and satisfying troubleshoots I "enjoyed" during my electrical career.