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Joined: Jul 2004
Posts: 9,923
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G
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I suspect those Vegas pools were concrete so bonding the water was not an issue. The water was a conductor and bonded everything in contact with it, where fresh water might not. Tesla is talking about a plastic tub, where the water is at a different potential than anything around it. If everything remains non-conductive for 5 feet or so around the tub, there is no real problem. If you have a grounded tile floor, you are going to feel that shot, even if it is just static electricity.
I bet, if you did nothing but punch a stainless bolt through that tub wall, in contact with the water and bond it, you would be fine.
680.26(C) says you should have 9 sq/in. tho


Greg Fretwell
Joined: Jan 2005
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Cat Servant
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No, Greg, quite the opposite.

Vegas started having problems with pools that were made entirely of plastic, or plastic-coated metal. Pools where the "tub" was trucked intact to the site, then set in the ground.

Add to these pools entirely plastic plumbing and a plastic pump, and there was no way - or seeming need- to bond the pool.

As mentioned before, it seems the very conductivity of salt water prevented voltage gradients from forming, while relatively non-conductive fresh water pools had issues.

Joined: Jul 2004
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G
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It is academic in pools and spas now anyway because we bond the water.


Greg Fretwell
Joined: Jan 2005
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"Academic" it may be, but there was some theory put forth here that was inconsistent with experience.

Does it matter? Yes, it does - as evidenced by that classic picture of someone 'grounding' a generator on a catwalk by sticking a rod into a bucket of dirt!

Joined: Jun 2004
Posts: 1,273
T
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Reno...

The physics describe above also under pins MHD power generators.

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

In a MHD design, the 'salt' used is typically potassium based.

The actual power density/ energy density is quite low. It's voltage potential is easily measured with a Fluke.

This Faraday effect does not occur in totally pure water. Btw, some areas of the country don't even have 'pure' water at the tap, potable, yes. So even the garden hose introduces more salts into the hot tub.

None of these units would be deemed to be 'salt water' tubs, per se. The salt concentrations are still so low as to merely taste bad.

The users get jolted because water is splashed out. Then when they exit -- obviously dripping -- they end up having one leg at zero potential/ the ground plane and their other still sticking straight into the hot tub.

If you're still unconvinced -- channel Dr. Faraday, Dr. Hall and the rest.

I've seen it, tested it, and cured it. BTW the hot tub in question was in Reno.

&&&

If a device has a very well shielded motor then the above effect figures to be totally suppressed.

I've lost track of how many tub owners have gone onto the Internet to complain about phantom voltages -- near their hot tubs.

They're on the Internet -- because the service electricians -- more than one -- can't cure their problem -- and don't believe them -- or don't know what could POSSIBLY be causing the problem.

The typical owner assumes that the equipment is shorting -- and that's that. Of course, a true short would trip the GFCI -- if not the circuit breaker.

BTW, the impressed voltage also does a cracker jack job corroding any metal it contacts. No-one connects this galvanic, stepped up, corrosion with the Faraday effect.

At all times, these are low energies... kind of like building up a static charge by shuffling across carpeting.

The ability of an AC current to build up and impress a DC bias in transformer steels is covered by Buss, and aluded to in Ugly's. (short circuit calculation section)

The AC current flip flops the induced field. But because of imperfections in the magnetic domains of the rolled steel, it actually develops a slight DC bias. It favors one orientation more than the other. This effect is also at a (very) low level. It's never brought up in ordinary calculations or class discusions. You could be in the trade for fifty-years and never have to deal with it. It's counter intuitive, too. We're ALL taught that AC is symmetrical. But nature is complicated -- and actually is always slightly away from idealized physics.


Tesla
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We can't rely on anything as science, can we? If we did, we'd be forced to repeal all those AFCI requirements.

After all, doesn't Paschen's Law bluntly assert that there can be no arcing faults at household voltages on copper wires:

http://en.wikipedia.org/wiki/Paschen%27s_law

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