While looking at Article 680.42 I have come to the realization that there is no exemption from a perimeter surface grid for spas and hot tubs. 2008 NEC. I have not been asking for this as part of the bonding. What am I missing?

Why would there be an exception? You have exactly the same risks. It may actually be more risky since they use an immersion heater in most spas.

Thanks Greg, I was expecting to see an exception for a spa or hot tub on a wooden deck. If the concern is the voltage gradients in the earth and the deck separates the spa from the earth- what's the hazard? Maybe the wood when wet could be an issue???

The other thing that don't make sense is the fact that we don't need a perimeter surface grid for a storable pool and it typically is setting right on the ground allowing a person to be outside the pool standing on the ground and have their hands in the pool water???

Immersion heat more risky? Better tell that to my water heater.

In our quest for 'safety,' are we chasing faeries and pixies?

George, I see where you are going. If this is a non conductive decking surface, I agree I am not sure how you bond it. I usually hear about the issue being a packaged spa dropped on a concrete or other type of paved deck.
I understood expanding this to the grass but I think they missed something.
Does the 2011 address non conductive decking?
I know that was the usual mitigation, adding a 3' deck around the spa.

Reno I would not be "shocked" if we did see something about bonding the water in homes with electric water heaters and plastic pipe. Most new water heaters do come with steel stub ups that would give you at least 9 sq/on of surface and it is bonded to the EGC but I doubt that would trip a 30a breaker.
I know that copper piping will, because my neighbor had an element open up to the water and it was like a bolted fault.
You could hear water boil for about a second and the breaker tripped.

Storable pools are a totally different breed of cat. All storable pool equipment is required to be double insulated.

WHat's next? Equi-grids for the kitchen disposal, dishwasher, and whirlpool tub in the bath? Heck, let's do the whole yard, in case someone later installs a birdbath.

Heaven forbid someone decide to shift the package unit over to the other side of the patio, or set it up in the garage in the winter. After all, they get filled with a garden hose, and can go anywhere.

I'll tell you where this will all lead. It will lead to a world where Billy-bob 'hillbilly engineers' some bit of kludge that is truly dangerous, everyone makes an occupation out of avoiding city hall at all costs, and every street will have some bitter harridan peering through fence slats hoping to cause trouble for the neighbors.

In about three or four code cycles it will be against the code to put electricity in a house at all!!! Everytime somebody invents a new widget, a new code chapter gets written to require its use, needed or not. Arc Fault, Ground Fault, Tamper Resistant, and in use devices have more than doubled the cost of wiring a house with no end in sight. The end result will be some really dangerous stuff thrown together to avoid calling an electrician at any cost.

Look who sits on the code making panels, what do you think there job is? Granted now some of the new products are great and they are real time savers. However just because someone invents something new, shouldn't mean that the code has to be changed and that the new product is required to be installed. Just my opinion.

http://www.nfpa.org/Assets/files/AboutTheCodes/70/TIA70-11-1.pdf

I once did a service change and was about to finish the job. I knealt down to label the panel, and recieved a "tingle" from somewhere. I got my meter out and checked the voltage to "ground" (literal earth) and recieved a reading of 117 volts. After troubleshooting I found an old furnace under the house that had been replaced by a heat pump system, but was not properly disconnected. It had "frayed wires" supplying it and it was touching the fuel oil line that was going to the tank located underground at the electrical meter location. The homeowner said his children were in a "kiddi pool" and kept complaining the water felt funny. He felt the water and could feel a tingle. Rather than reporting it to someone, he just moved the pool farther from the house. Thankfully no one was hurt and I disconnected the old furnace under the house. The bonding grid may have come in handy here, but again you can't prevent "dumb" people from doing dumb things. You always have that potential of hazard when someone does not do their job correctly. I still have the photo of the readings I got on my screen saver with my other family photos.

You sweat when in a hot tub. Gradually the salt content rises.

It exists as ions in solution -- and they are effected by magnetic fields.

( Which is why sub-sea transmission is done by DC only. AC just stirs the ocean and kills transmission economics.)

It is critical that all in one hot tubs have a true ground from the three prong plug. A GFCI is built-in -- but a true ground is necessary to bleed off the voltage induced into the pool as it circulates past the magnetic fields of the pump motor - - and, no, the typical design does NOT have a Faraday cage in anyway shape or form blocking the field windings from sweeping through the bath water.

This kind of induced voltage can reach painful, even lethal levels. I've personally tested voltages as high as 47V from bath to ground. Multiply that by your wet sweaty skin and the mass of circulating salts and you have a real hazard.

The help line from the tub manufacturer was helpless/ clueless.

http://en.wikipedia.org/wiki/Hall_effect

The physics of the energy build up is due to the Hall effect. The salty bath water is the conductor and the pump motor provides the electric field and drives the ionic water across the lines of force.

The ions are the charge carriers.

MHD power plants are based on the exact same phenomena -- flipped. They use hot coal fired gases injected with K or Na to rocket through an expansion nozzle wrapped in DC field windings and in passing directly induce DC power.

http://en.wikipedia.org/wiki/MHD_generator

When a hot tub is placed on a non-conducting surface and the voltage is not bled off it can build to astounding levels. It ends up becoming a gigantic big wet capacitor. Then one fine day the deck is wet and a path to ground is made. Wham! Trouble.

Tesla- Way to much information. If this were as threatening as you indicate there would be an uproar by the public about the hazards of Spas and Hot tubs to the extent that no one would purchase them. I believe they are safe and the NEC requirements are all that are needed for electrical safety.

great, the code (680.42(b), referes to manufacturer's instructions, which usually say 'call an electrician'

more mobius strip logic, with our trade caught in the vernacular vortex....

~S~