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Equipotential Plane #168277 08/30/07 10:28 PM
Joined: Jan 2004
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George Little Offline OP
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Article 682 Section 682.33(A) talks about installing an equipotential plane and I would like to know what this would consist of material wise and would we expect to see one for electrical equipment associated with a small fish pond about 12 feet in diameter.


George Little
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Re: Equipotential Plane [Re: George Little] #168278 08/30/07 11:07 PM
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gfretwell Offline
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I have been trying to figure out what 682 really means for 2 years and I can't find anyone who knows enough to start an argument. I suspect it is largely being ignored. Installers are using all plastic enclosures and saying that relieves them. I am stil wondering about the pumps and air blowers you see on a golf course pond.

Personally I see this as bonding the steel in a pad under the equipment or using the copper grid you put under pool pavers in the dirt if this is unpaved ... but folks say that is overkill.

You certainly have to bond all pipes, racks, strut and metal enclosures


Greg Fretwell
Re: Equipotential Plane [Re: gfretwell] #168292 08/31/07 06:55 AM
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George Little Offline OP
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Thanks Greg- I agree with you, nobody wants to make any kind of statment about it. The best I been able to do is get a rather nowlegable code guy from UL who will remain nameless say " Well probably we need a grid like called out in 680 for pools" These installations are going in and being approved but the code is weak on details for this item so the inspector are probably all over the map on this one. Michigan will be on the '05 NEC starting 11/23/07 and I'd like to know what is being approved by others. Maybe I'll submit a question to Charlie Trout and see what he says.


George Little
Re: Equipotential Plane [Re: George Little] #168307 08/31/07 02:21 PM
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gfretwell Offline
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When you read it, 682 is more restrictive in some areas than 680. You don't need any grid under a pool pump or the disconnect for it.

It is amazing that these things languish in the ozone until a week after the code gets adopted by the AHJ. This is something that could cause a lot of trouble if you really took it to the logical conclusion. We could really blow up in your face if you started redefining "natural bodies of water" and didn't put a limit on the man made bodies of water this applies to. Is this also for a little koi pond on your yard?
I think things like golf course lakes and retention ponds are exactly what we are talking about and there are millions of them here in Florida. Virtually all of them have some kind of electrical equipment in them. Usually they are maintained by the greenskeeper or building maintenance man. I would be happy if they just got rid of the "flying" wirenut splices and missing EGCs wink


Greg Fretwell
Re: Equipotential Plane [Re: gfretwell] #168527 09/07/07 04:48 PM
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SteveFehr Offline
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We deal a lot with equipotential planes in the IT field. It can be as simple as copper mesh or bonded rebar in the slab; in IT centers, it's common to have the (metal) false floor bonded to act as an equipotential plane. (Also helps dissipate harmonics-the capacitance of an equipotential plane to ground tends to clear higher frequencies extremely well.) But there really is no one standard industry definition- it's simple a plane at equal electrical potential. Conductive matting is another means- ask anyone who deals with explosives in a workshop setting, for instance, and they can tell you exactly what you need to do to completely eliminate shock hazards.

With no set definition, in the end, it's going to come down to an AHJ ruling.

Re: Equipotential Plane [Re: SteveFehr] #168544 09/07/07 11:30 PM
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gfretwell Offline
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Back in the 70s and 80s we had extensive bonding of raised floors but after IBM cleaned up their act and used better shielded power supplies in their computers it became a whole lot less necessary. I have been in 308x computer rooms where they used 1/2" copper pipe, in a grid, to bond every floor post. Even IBM said that was overkill.
A lot of times regular hardware or software problems got blamed on "noise" and these draconian measures were taken.
I have had to come in at night and fix the hardware problem to save the IPR's butt when all the bonding didn't fix anything. The story was always "it was a couple problems yada yada".


Greg Fretwell
Re: Equipotential Plane [Re: gfretwell] #168547 09/08/07 10:31 AM
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leland Offline
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680--

In MA. We have gone back to the 2002 code for pool bonding.
How this effects 682 I'm not sure, I assume the same way as 2002.

My understanding from our mandatory code reveiw.

Re: Equipotential Plane [Re: leland] #168558 09/08/07 08:47 PM
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gfretwell Offline
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I think the 2008 probably has it right on the pools. A single #8 looping the pool deck to bond it or bond the rebar if present.

I also think it is reasonable to bond the pads under pond and lake equipment to the EGC and any exposed metal that might present a gradient. These guys working on this stuff have a very good likelihood of just climbing out of the lake and being wet.


Greg Fretwell

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