On Tue, 26 May 2009 05:33:53 -0700 (PDT), firstname.lastname@example.org wrote:
The legal answer is to either find a way to bond the steel in the slab
to the metal parts of the spa or build a non-conductive deck over it,
3' out from the spa or more.
Our spa dealer has a PVC deck kit for doing exactly that. It is
necessary if you get a permit to set your spa on an existing slab.
It takes two (electrical contacts) to get shocked. Let's say the cement is
one, what is the other one?
It is very unlikely to get tingling in the fingers unless they are touching
something (metalic or liquid) while you're standing on cement.
Of course that's not normal -- it is downright dangerous. Do not perform any
more "tingling" tests with your body. It could turn into a life-threatening
shock without notice.
I'm guessing that the cement, when wet, is equal or close to a ground
potential. That would mean that the spa water is at fault, carrying voltage
when it shouldn't.
You can find out for sure by using a multimeter to measure the voltage or
(1) the ground pin from a grounded outlet, to the wet cement (or a metal
object placed on the wet cement)
(2) the ground pin from a grounded outlet, to the spa water (or a metal
object placed in the spa water)
If you find voltage/current in any of the above, then something is wrong. It
is more likely you'd find voltage in (1). If indeed you do, then the next
step is to debug the spa equipment.
Before you do, make sure the outlet supplying the spa is wired correctly and
there is no voltage on the ground pin. One way to test is to measure the
voltage between this ground pin and another outlet's ground pin. If there's
a voltage -> faulty ground.
If there is no voltage, then the more likely culprit is the spa equipment.
That is harder to test without seeing a schematic or the real thing.
My theory and 2 cents....
It could be than the slab ground is at a different potential than the
tub ground, this difference causes current to flow between the two
grounds (via your body), another name for this is a "ground loop".
These grounds could be at a different potential because of corrosion
on one of the ground connections (tub or slab) and that is acting as a
resistor on one of the grounds. Ideally any outdoor tub should be re-
grounded with a rod to put the slab at exactly the same potential as
the conduit/box, which I assume is grounded only to the house ground.
Have an electrician check it out, re-do all the ground connections,
and install a local grounding rod not to re-bond the neutral but to
simply make the slab and tub chassis equal potential by re-bonding the
tub chassis/box to the slab. But have someone check it out who doesnt
have to use a human body as a voltmeter.
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