Hot tub getting a small shock

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On Tue, 26 May 2009 05:33:53 -0700 (PDT), snipped-for-privacy@optonline.net 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.
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wrote:

Jeff-
I think you've hit on the possible cause.
cheers Bob
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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.
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You are right, I can touch the spa water and wet cement and get the small shock, but not when the cement is dry. Are you saying this is normal and mabye I just noticed it?
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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 current between
(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.
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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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