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Thread: Stray Voltage

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    Stray Voltage

    We bought a house that had an inground fiberglass pool installed last year.
    We are under the 2005 rules and in a rural area which only required a construction permit and no inspection.
    The pool has a ladder, led light and rail.
    The equipment pad is 20 ft from the pool and there is a pump, heater, timer and salt water generator.
    An 8ga bond wire connects the pump, heater, salt water generator and then goes out to the rail and ladder cups and then the light.
    I notice when kneeling on the concrete deck and touching the water, I get a very slight "sting".
    However, if I crouch on the deck with my shoes on and touch the water - nothing.
    I am also measuring .5 volts dc via my digital meter with the + probe in the water and the - attached to a 8ga rod about a foot in the ground just past the deck.
    No AC volts are measured.
    I know - I know - you are going to say the concrete isn't bonded and that is why it is there and that it "should" have had a grid under the concrete or attached to the rebar. I agree. However, I am not certain there is rebar in the deck. It is 4" thick by 4' all the way around. I talked to the pool company that did the work and they are not sure either. I frankly don't know how they wouldn't know, but that is a topic for later discussion.
    I also know that when I do a continuity test, I am getting continuity at all levels of the bonding - i.e. both cups of the rail and ladder, the light, etc... so there are no breaks in the wire.

    Our power line and phone line are buried and the grounding rod for them is beside the equipment pad.
    I had the POCO come out and disconnect the meter, then the transformer, etc... Still there. They also disconnected the nearest neighbor a couple acres over and still there. We read the same dc voltage in their pond!
    Therefore, I know it is not coming from our property as far as the POCO is concerned.
    I had the phone company come out and disconnect their stuff at the pole and still there.
    Just as some added info, we have an antenna tower on the side of the house that is connected to its own burried ground rod.
    On that antenna is our dish tv dish and a digital antenna for off air which both have a ground wire attached from them to the tower.

    I guess what this long post boils down to is:
    Where would the DC voltage be coming from?
    Is it possible that we would feel .5 dc? I am thinking the salt water is helping increase that but .5??
    The POCO registered the same number, so I know the readings are correct.
    They are stumped as am I.

    Short of tearing out several thousand dollars worth of concrete, is there anything I can do such as creating an external grounding ring around the pool?
    I am able to dig all the way around the concrete including under it if needed, but not sure what too do at this point other than keep everyone out for safety sake.
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    Ohm_Boy's Avatar
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    Re: Stray Voltage

    Odd. One should not be able to feel 0.5 volts Dc. I think that wet skin has a resistance around 1Kohm or so, so with 0.5 v and 1000 ohms, there should be no more than 0.0005 amp, or half a milliamp.
    Back when I was doing control systems engineering, anything below 25 VAC was considered safe if exposed (our design rules). I don't remember the DC 'safe' levels, but I can assure you it was over 0.5VDDC.

    I suspect that something else is happening other than a half volt of DC. Any chance you could check with an oscilloscope instead of a meter? It might be a frequency thing.
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    Mod Squad JohnT's Avatar
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    Re: Stray Voltage

    When you measure 0.5VDC, what are you measuring between? Pool deck and water? Same question for the neighbor's pond.

    Anything like a substation, sewage pump or any unusual electrical equipment anywhere in the area.

    I'm as stumped as you are, so I'm just throwing out ideas for the most part. Keep us updated.
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    Re: Stray Voltage

    Between the pool water and a ground rod stuck about a foot in the ground just past the deck.
    I can also measure it from the pool to the deck if I throw some water on the deck.

    For the pond, it is from the pond to a rod about a foot in the ground, about 3 ft back from the water.

    If I go from the pool water to the railing or ladder, I also get the same measurement.

    Nothing unusual in equipment.
    While we have always measured vdc, we had been getting .3 VAC that we are no longer registering.
    The poco has been very helpful with adding some extra grounds on poles and checking some transformers, capacitor banks, etc... in the area.
    We haven't measured VAC though in over a month but the VDC has continued to be there.
    I only mention the VAC because it had been there, but neither the POCO or myself are measuring it.
    I had my friend over who is a residential electrician and he said he has no idea where the VDC would come from and that possibly short of the deck not being bonded, he has no ideas either.
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    JasonLion's Avatar
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    Re: Stray Voltage

    I suggest getting a fitting to bond the water. Many companies make fittings that allow you to do this, for example these people. I can't figure out where your voltage could be coming from, but regardless that should take care of it.
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    Mod Squad JohnT's Avatar
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    Re: Stray Voltage

    If your ladder and light are bonded, it seems odd that you can measure voltage between the ladder and water.

    Although a bonded deck would keep you from noticing the problem, you still have some kind of problem.
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    Re: Stray Voltage

    Hey there NotBob~~

    DH and I were wondering: If you turn off the breaker/power for your SWG, does the condition still exist?

    Our SWG was confusing the heck out of our Chemtrol until we did some water bonding.

    Good luck with this--keep us posted~~

    Lana
    23,600 gallon, refurbished 1960's inground concrete, Jandy sand filter w Jandy 2 hp variable speed pump, Pool Pilot Digital SWCG+Chemtrol 2100+CO2 tank; PebbleTec White Pearl with 10% Cobalt Blue Dark Beadcrete by Olympic Pool Plastering, Georgia. Taylor K-2006 Test Kit; Aqua Check Salt test; LaMotte borates test, and Jack's Magic Sequest test kit; SparklyPoolitis level: extremely high.

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    Mod Squad Bama Rambler's Avatar
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    Re: Stray Voltage

    As said above, you can't feel .5vdc.
    You don't say where you live and that affects different things.

    Try this. take your volt meter and kneel on the deck and check the voltage between your skin and the water. You may need to wet your skin to get the resistance lowered enough to pass voltage.

    Having said that, I agree with bonding the water. The water bonder is a good choice but you can do the same thing with a stainless coupling and nipple. Drill and tap the coupling to attach a bonding lug and you're good to go.
    Dave J. TFP Moderator
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    Re: Stray Voltage

    I appreciate everyone's response!

    We live in Northwest Ohio.
    I will try bonding the water this weekend and see what happens then let you know. (If I would go with a commercial product, does it matter where I bond the water? I know they have a plate that goes in the skimmer or as Jason mentioned, the pipe that connects at the pump filter - so is 1 better than the other?)


    Also, if we turn the breaker off for the swg, it does still exist. Even with the poco transformer disconnected at the pole it still exists.

    I tried a few things last night and found that the sting is felt more in the deep end.
    That is where the light is - so I am suspicious now of the light. I also found that when I have one hand on the rail or one hand on the ladder, I do not feel it. Guessing since those are bonded, that is why.
    Also, if I put my hand in near the ladder I do not feel it as well. Once I get about 2-4' away, then I feel it again.

    One more piece of info that is leading me towards the light...
    We have an inground spa that spills over into the pool. I get no sting and read no voltage in it.
    The only thing that is different is that the pool has a light and ladder, leading me back to being suspicious about the light?

    Since the light and ladder is the only thing touching the water, I am going to pull the ladder tonight and see what happens.

    Is it possible the light could be causing the water to be energized? Even with the entire power off? Since it looks to be stray voltage, if the light isn't properly bonded, which we "believed" it to be, could that be causing the issue and bonding the light properly fix it??

    Thanks again to everyone!!
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    Ohm_Boy's Avatar
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    Re: Stray Voltage

    It has to be coming from somewhere, and it does not *seem* to be directly powered by the POCO's supply to your home, nor to the neighbors, and it does not seem to be powered via Telco line. So what's left?
    For one, cable TV distribution coax (the big coax that feeds the dist. amp, not the drop to a home) generally has about 90vDC floating on it. You can definitely feel them.

    Beyond that, there must be a power path through the earth and crossing the pool, or something nearby is generating, or perhaps there is an induced voltage into an unbonded/unshielded conductor.

    Are there underground POCO feeds to the area? Are there any transmission lines nearby? Like those really big hundreds-of-kilovolts lines? How about a radio station or microwave transmitter? It'd take a fair sized radio signal to produce an induced tingle depending on the frequency.
    Oh, speaking of frequency, AC meters are designed to read RMS voltage of a sine wave at 60Hz. They don't do as well with odd waveforms or different frequencies. This is why I mentioned testing w/ an O-Scope earlier. It would show even a high-frequency waveform, and you might see some real voltage with one.
    Back to induction - if there is an induced voltage, it might, in fact, be on the light wiring, if it is not shielded in conduit. Especially if the light wire has been disconnected from power and left open. You could probably test-eliminate that by disconnecting the light wires from power, connecting the two conductors together, and connecting them to the bond wire. That should remove any potential voltage in the wires themselves.
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  11. Back To Top    #11
    Ohm_Boy's Avatar
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    Re: Stray Voltage

    If you have a few hours to kill just reading, then please to enjoy...
    http://www.mikeholt.com/technical.php?i ... ettersmenu
    http://www.neetrac.gatech.edu/publicati ... e_2007.pdf
    ...and this one, which gets really interesting to read once you get past the backbiting and spitting at the beginning.
    http://www.mikeholt.com/newsletters.php ... =#comments
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    Re: Stray Voltage

    If the ladder and light are bonded, then the water should be bonded.

    When the power company disconnected the power, did they disconnect the neutral? The neutral can be a source of stray currents, especially if the neutral service is insufficient or if there is something disrupting the power frequency.

    If you're near certain things like a pipeline, the pipeline, or other infrastructure, might be using impressed current cathodic protection, which can lead to stray current nearby.

    Impressed current cathodic protection works like an anode by pushing electrons towards the metal to keep it from losing them from the metal (oxidation). It uses a DC source to provide a voltage, which keeps the metal charged.

    Can you measure any current flowing from one point to another?

    One thing you will probably notice is if you have any sort of a cut on your finger, you will feel much more of a shock at the cut point.

    If possible, AC voltage should be tested using a "True RMS" meter vs. an "Averaging RMS" meter.

    http://www.youtube.com/watch?v=XUdRW0XgYQs

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    Re: Stray Voltage

    JamesW, not sure if they disconnected the neutral. They are willing to work with me, so I will have them do that at my house and the neighbors.

    With further testing this weekend:
    Removed the ladder. Disconnected the light wires (black and white) from the transformer.
    Created crude water bond device - took 2" id stainless pipe. Drilled and tapped screw into it then attached bare #10 ground wire (didn't have any 8) to it and wrapped about 20 ft of the wire around it. Connected the other end to my bond wire.
    While feeling the sting on a cut finger at the deep end of pool, had wife lower this into shallow end. Sting went away after a few seconds.
    As she removed it, could noticeably feel it come back.
    Also while it was in the pool, I got a reading of .7 vac from the water to the rail (which is not in the pool, but the cups are bonded).
    When it was out, no voltage VAC but still the .5 vdc.
    I tested for continuity between the pool and rail and pool and water on the deck. Nothing. With the device in the pool, I get continuity between the pool and rail and pool and water on the deck.

    Ohm_boy had mentioned on the light, connecting the 2 wires together then connecting to my bond wire. I tried that and noticed no difference on anything. I also ran an additional wire from my bonding and then tried testing continuity while the light wires and bonding wire were connected. I did not get any. I did not expect to get any as I thought only the niche would be bonded and neither of the black or white wires?

    I think the next step is to bond the water properly.
    JamesW, not sure if they disconnected the neutral. They are willing to work with me, so I will have them do that at my house and the neighbors.

    With further testing this weekend:
    Removed the ladder. Disconnected the light wires (black and white) from the transformer.
    Created crude water bond device - took 2" id stainless pipe. Drilled and tapped screw into it then attached bare #10 ground wire (didn't have any 8) to it and wrapped about 20 ft of the wire around it. Connected the other end to my bond wire.
    While feeling the sting on a cut finger at the deep end of pool, had wife lower this into shallow end. Sting went away after a few seconds.
    As she removed it, could noticeably feel it come back.
    Also while it was in the pool, I got a reading of .7 vac from the water to the rail (which is not in the pool, but the cups are bonded).
    When it was out, no voltage VAC but still the .5 vdc.
    I tested for continuity between the pool and rail and pool and water on the deck. Nothing. With the device in the pool, I get continuity between the pool and rail and pool and water on the deck.

    Ohm_boy had mentioned on the light, connecting the 2 wires together then connecting to my bond wire. I tried that and noticed no difference on anything. I also ran an additional wire from my bonding and then tried testing continuity while the light wires and bonding wire were connected. I did not get any. I did not expect to get any as I thought only the niche would be bonded and neither of the black or white wires?

    I think the next step is to bond the water properly.
    These guys want $145.
    These guyswant $35. Anyone see why I would not go with the cheaper one or if there is a better way I should be doing this?
    I know ultimately I still have a problem I need to find the source of, but if I can at least get the shock to go away, we can continue researching it.

    Thanks again everyone!!
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    Melt In The Sun's Avatar
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    Re: Stray Voltage

    I'm not sure I'd get either one...perhaps I'm crazy, but couldn't you just drill and tap hole in a pipe and install a metal plug connected to the bonding wire?
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  15. Back To Top    #15
    Ohm_Boy's Avatar
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    Re: Stray Voltage

    Well, these guys have a water bonding pipe that is UL listed... http://www.waterbonder.com/

    I *think* you need to have 9 square inches of surface contact with the bonding 'device' to be within NEC 2008.
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  16. Back To Top    #16

    Re: Stray Voltage

    Yep, that's the $145.00 one....
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  17. Back To Top    #17
    Melt In The Sun's Avatar
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    Re: Stray Voltage

    Quote Originally Posted by Ohm_Boy
    I *think* you need to have 9 square inches of surface contact with the bonding 'device' to be within NEC 2008.
    Didn't know that; thanks. Into the leaky memory bank it goes...
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  18. Back To Top    #18
    Ohm_Boy's Avatar
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    Re: Stray Voltage

    Quote Originally Posted by notbob
    Yep, that's the $145.00 one....
    Oh.
    The bad thing is that chlorine will tend to eat the metal bonding pipe too. Those looked like some pretty heavy duty stainless, so it could hold up for some time though. But still... $145. Ouch.

    As I ponder, I think "If it were me, I think I would get my hands on a piece of type K copper pipe and a grounding clamp for pipe (like this: http://www.amazon.com/4-UL-Copper-Pi.../dp/B000LF7VF6, and put 5 or 6 inches (or so) of pipe inline somewhere, then affix the clamp to it, and connect the bonding wire to that."
    I think I'd call it 'testing'. Heck, Maybe I'd even test it.
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  19. Back To Top    #19
    Mod Squad Bama Rambler's Avatar
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    Re: Stray Voltage

    You can build one yourself using a stainless coupling, a 2" nipple and a bonding lug. The 2" nipple alone gives you a little over 9 sq in of surface area. If you buy everything from Grainger it's about $40.
    Dave J. TFP Moderator
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    Re: Stray Voltage

    I had the same thing,figured out it was because in my panel in my house the grounds and neutrals were indeed being shared in the box,which was sending voltage back thru the neutral.I which I know is a no-no unhooked the ground from my house and drove a seperate ground temporarily until I work on my box inside which will be installing a ground lug and seperating grounds and neutrals

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