I always said that the correct way to compensate for voltage gradients was to install the mat like the code had originally. Welded wire mesh was never an acceptable alternative. Then along came the 2008 NEC and everybody breathed a little easier. Well, here is a study that shows that The alternate means described in 680.26(B)(2)(b) of the 2008 NEC may not provide adequate protection to the swimmer and person walking on the deck.

I will say I told you so.

"TOLD YOU SO"

http://dl.dropbox.com/u/3736785/680-26.PDF]

The market had responded with the #8 copper mesh, just about the time they changed the code.
The last time I talked to a pool contractor (back in the Fla 2005 cycle) they said a #3 rebar grid like they use in the shell was a lot cheaper than the copper and it was something the pool steel guys knew how to do.

The rebar grid is probably a good way. The copper mat was the alternate method. And now we have the alternate to the alternate method - which according to the data, is useless. Way to go.

I don't know if I buy into any of it anymore.

I have read some compelling research and substantiation on both sides of the argument. One paper written buy Don Zipse of the IEEE indicates that equipotential bonding is the cause of step and touch potentials at and around pools. Now you have this one from a firm in Georgia indicating more equipotential bonding is needed.

How can two studies on the same subject matter have completely opposite results?

It reminds me of the egg. Just about every other month or so, experts change their mind on whether or not the egg is healthy to eat. Today, they are great for you. Tomorrow, they are the cause of all humanities ills.

I believe that most stray current issues is/are a power company issue, and that a bonding grid is merely putting a band aid on the problem that they already know exists. Essentially, it boils down to this - our power grid is obsolete.

But what is the answer? How can power companies install a much needed ground wire (4th wire)? The cost would be astronomical. So what do we do? Or, are we doing it?

Nick, are you saying you don't think the customer should be re grounding the neutral?

I do understand the concept. It is inevitable that we are returning a significant amount of neutral current through the earth, particularly in wye distribution.

I get some pretty high readings, looking at that bare copper running down the power poles in my neighborhood. I do think a good equipotential grounding grid that picks up everything near the pool in one unified matrix is a safe work around. If that is integral with the Ufer in the slab of the house and everything else that is "grounded" you become that bird on the wire and it is not important what potential the whole thing is riding at. It certainly is not going to be "zero volts" compared to just about anything else.

I agree with gfretwell, that the only real thing we need to be concerned about is that the potential is the same in and around the pool. So long as that is the case, no current will flow. The biggest danger is to be in the water as it is (with it's added chemicals) the most likely to conduct and harm a person. At some point away from the water line the potential for harm drops. As you say though, they will go back and forth and someday settle it.

greg- no i was not stating that

Nick, if you were not "floating" the neutral (like we do with sub panels), what would the 4th wire do?

The question came up at ECN, what about a non conductive deck with a spa sitting on it. What do you bond? How do you bond it?

The requirement for equipotential bonding of perimeter surfaces at outdoor spas goes away under the 2011 NEC.

Until then, the code requires the single #8 ring with four pionts of connection to the spa EGC, any other fixed metal parts, and the metal parts of the spa.

680.42 references Part II which contains the provisions of 680.26(B).

Where does the #8 go if this whole thing is sitting on an elevated plastic deck?

What amazes me is that this was not taken into consideration from square 1. It seems like we have this new "trial-and-error" type of CMP-17, and it has been like that now for a few years. I hope NFPA changes out most of the players on this code making panel. Does anyone know if this panel has changed any of its members in the last few years?

It goes on the green plastic screw. That is listed for use!
Mounted on the rest of the non-conductive material.
Smile.