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Old 07-04-2009, 09:37 PM   #1
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voltage potential around in-ground pool


I talked with a friend with an in-ground pool. He gets a slight electrical shock when getting out of pool (half in water and touching the wet cement walk around pool). He asked me how that was possible. I replied that there has to be defective or no electrical grounding. He has turned off all circuit breakers (cb) to both motors and the lights. A slight potential was still there. Also, he has measured for vac leakage out of cb'ers and potiential was still there. I've read about grid bonding and assume this is a possibility. Yet I think there still has to be a hot wire around the pool for the potential. Lastly, I wonder about the ground (earth) at pool pump verses the power company ground. What if his ground was better than the power company ground? This would also create a difference of potential. Any advice/recondementions would be greatly appreciated. Also, I advised gfci circuits.

Thanks, Logi98

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Old 07-04-2009, 10:13 PM   #2
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voltage potential around in-ground pool


Installing a GFI breaker on the Pool pump motor circuit is a good idea, and probably a Code requirement. But the "Shocking" mystery must be solved first. If, as you say you turned off all circuits and still getting shocked, there's a possibility that a "renegade" live wire is left from a previous installation!The devil is in the Details! Don't Drink and Drive!!!

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Old 07-04-2009, 10:15 PM   #3
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voltage potential around in-ground pool


This is an issue of a poor bonding grid, or not having one at all. This is not a "hot wire around the pool" issue.

The ground from the POCO is actually from the neutral bond in the main panel. The earth itself has nothing to do with the electrical ground that causes breakers to trip on a short circuit. So adding a wire from a motor to the earth or a ground rod will serve absolutely no purpose.

Read up on "equipotential bonding". Google is your friend.
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Answers based on the 2008 & 2011 NEC.
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Old 07-04-2009, 11:34 PM   #4
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voltage potential around in-ground pool


I'll just start by saying there is nothing we can do here to solve your problem other than point you in the right direction.

I would like to mention that Speedy is correct your friend likely has a defective bonding grid for his swimming pool or an improper one or none at all. However you should understand that current exists in the earth almost everywhere and it may be a result of stray voltage and or current (neutral to earth current) or fault current. Question is.... is it excessive and where is it coming from? This is all due to the utilities multi point neutral grounding system where earth and the utility neutral play partners in returning neutral current to the source (transformer). It is important to note that stray current is not fault current.

You need to request an inspection by a codes official who will then request a NEV (neutral to earth voltage) analysis from a power company technician/engineer.

They will likely begin by asking you to turn your main breaker off. They will then take a test measurement of NEV around your pool. If the NEV deminishes to an acceptable level then the problem is with your electrical system.

If it doesn't decrease then they will pull the drop out fuse of your transformer. If it still doesnt decrease then it is a utility neutral problem or a service neutral from a closeby neighbor or some other outside source. They likely will install a neutral isolater device to solve the stray current and or voltage problem if it is coming from the utility.

Proper bonding of metal around the pool will generally eliminate potential differences but will also mask a stray voltage/current problem.


So two things

1.) You need to be sure you have a bonding grid around your pool in accordance with NEC article 680.26 2008
2.) Have a neutral to earth voltage analysis done (NEV Test) to determine if it is your problem or the utilities or if no problem exists other than improper bonding of metal around your friends pool. And if it is stray voltage and current or fault voltage and current.
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Old 07-04-2009, 11:35 PM   #5
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voltage potential around in-ground pool


I understand the grid problem, however, for there to be a difference of potential doesn't there have to be a potential or leakage from a hot wire? With all circuit breakers off and no leakage has been measured how else could there be a shock hazard?
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Old 07-04-2009, 11:42 PM   #6
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voltage potential around in-ground pool


Nope, neutrals are current carrying conductors and therefore have potential though not of the magnitude of ungrounded (hot) conductors. A hot to ground is a fault and is not considered stray voltage. You need to determine which it is. However don't test by seeing if you still get shocked it may be your last one.
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Old 07-04-2009, 11:55 PM   #7
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voltage potential around in-ground pool


Thanks for your help. If there was a bad neutral connection at the power company (pole) then would the pool have a better ground causing a difference in potential between the two points?
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Old 07-05-2009, 12:10 AM   #8
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voltage potential around in-ground pool


No it would be no better than the transformer ground. Remember all neutral taps at the transformer also have an earth grounding conductor ran to a ground rod at the bottom of the pole. Turning the main breaker off at your home will effectively remove all neutral current on your side of the service entrance unless neutral current is getting to the pool through the earth from an outside source. An example would be a buried lateral service to a neighbors or your lateral service that has a faulted neutral to earth or even a hot to earth that is placing your pool and surrounding metal in that potential gradient as the current uses the earth to get back to the source (transformer). The pool just happens to be in the way....

Suffice to say you have a stray or fault problem at your friends pool as you should not get shocked if you have a equipotential grid that is properly installed. It is likely that getting shocked is not normal to say the least and I would suspect you have a fault on the homeowners side of the utility or you have a stray voltage problem originating on the utility side of your service.

When your friend gets out of the pool is he touching a metal hand rail or just getting out onto wet concrete?
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Old 07-05-2009, 12:19 AM   #9
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voltage potential around in-ground pool


To my understanding he gets a slight shock getting out onto the cement and the shock is worse if it is wet. He has measured less than 3 vac from the ground rod at the pump to the pool water or wet cement.
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Old 07-05-2009, 12:30 AM   #10
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voltage potential around in-ground pool


Have your friend turn his main breaker off and take a measurement from the concrete to a metal object... the pool pump would be good. See if the voltage disappears or reduces. Do not place yourself in series with any concrete or metal around that pool. BTW the ground rod at the pump, if that is what they are using to ground directly to the pump, is pointless.
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Old 07-05-2009, 12:46 AM   #11
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voltage potential around in-ground pool


With the cb'ers off he measures about 3 vac from the ground rod beside the pump to the wet cement. He mentioned that when he removed the copper grounding wire from the rod and measured from the rod to cement the voltage dropped to about 1.5 vac. All this information I'am passing on was from a phone conversation with him earlier this afternoon. I might need to go visit and see exactly what he is doing.
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Old 07-05-2009, 01:11 AM   #12
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voltage potential around in-ground pool


Is that ground rod for the pump only or is it the ground rod for his electrical service.....and he is grounding the pump to it ? The pump should not be connected/bonded to any earth driven rods. It should be bonded to the other metal and equipment around the pool.
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Old 07-05-2009, 01:21 AM   #13
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voltage potential around in-ground pool


There is a power panel at the pump house with the grounding rod. This power panel is seperate from the house panel which also has a grounding rod. What is BTW? Also, he is in the process of "rent-to-own" for this house.

Last edited by logi98; 07-05-2009 at 01:23 AM.
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Old 07-05-2009, 01:29 AM   #14
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voltage potential around in-ground pool


Gotta go for the evening.

FWIW 3 vac is about where most people will complain of tingle voltage. Measuring 1.5 volts to the earthed rod and the concrete would be in the realm of an acceptable stray voltage. I would expect that.

Heres something to read through while I get some sleep....

http://forums.mikeholt.com/showthread.php?t=86958
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Old 07-05-2009, 01:31 AM   #15
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voltage potential around in-ground pool


Thanks Stubbie, catch you tomorrow. Thanks for all your help.................logi98

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