Interesting Shock Issue...

[notbob]

So here is one for the experts...

We are currently troubleshooting a shock issue in a pool.

Rural setting
Single panel in home
240v GFI breaker supplying power to equipment
Inground Fiberglass
Pool Light
Metal Ladder
Metal Rail
Un-reinforced Concrete

Pool light is a plastic fiberstar series which requires no bonding. It is 12v.

Single #8 running around under concrete, connecting to both cups on the rail and ladder, then running back to pump and swg, where is connects to a single line running between those, with a properl bonding lug connector.

There is about 1.5 volts showing in the pool.
Have done all the usual stuff, turned off the main breaker etc...
Voltage is still there.

I know the issue is the concrete is not bonded so there is a difference in potential and that will need to be addressed.
That will be taken care of later.

However, we are trying to find the source of the problem, which I believe is the neighbor as the pool is pretty much centered between the neighbors pole/transformer a few hundred yards and their own pole transformer about 50 yards away.
The poco has been out and disconnected the homeowners meter as well. They said they will have to schedule down time to check the neighbor.
All connections in the panel and the wiring for the pool equipment is correct.

The interesting thing is the voltage is on the bond wire.
We found this by removing the pool bond wire (which is buried) from the motor/swg.

With the pool bond wire lifted from the motor/swg bond wire:
I have a ground rod 2ft in the ground, 8 ft from the pool.
When I connect a wire to it, then touch the bond wire coming from the pool, we get the voltage.
When I connect a wire to it, then touch the bond wire that is connected to the motor and swg, nothing.

With the wire connected to the motor/swg, we read 1.5 volts in the pool and get the shock
With the wire disconnected, no volts in the pool and no shock

I guess what is a bit puzzling is that since the bond wire has the voltage on it, and the bond wire is connected to the metal ladder, I would expect to feel it all the time, unless I removed the ladder.
Only feeling it once we connect to the motor/swg - doesn't really make since to me. All that has happened now is that we have put those 2 pieces of equipment at equipotential with the handrail and ladder. Why would we feel the shock only when it has been attached to the motor/swg? Is it because the pool equipment is grounded via the panel and with the stray voltage problem it is felt??

Any thoughts/opinions?

(again, I know we are feeling it because the concrete is at a different potential and that will be addressed, it just boggles me that since the bond wire has the voltage and the source is not the motor/swg - it just doesn't make sense we only feel it after connecting to them?)

 

[JohnT]

1.5 volts with respect to what? Where is the other meter lead connected when you measure that 1.5V? I'd assume ground, which is what your deck is going to tend to be.

Most of the time the source of the problem is inadequate grounding by the power company along the transmission path. As current flows through the neutral, a voltage drop occurs due to wiring resistance, but that same drop doesn't occur on the ground because no current flows through the ground lead. In rural areas where there are longer runs between service locations, the voltage can get high enough to cause the issue you are seeing.

 

[notbob]

John,

The ground lead was attached to the ground rod I drove for testing, which is 2ft deep, 8ft away from the pool.
The positive lead was touched to the bond wire coming from the pool.
That is where the 1.5 volts is.

My guess is the voltage is actually higher, perhaps on a different frequency or something as we really shouldn't be able to feel 1.5 volts, however with salt water I know it does drop the level to which you can feel it.

If I do the same test as above, but touch the positive lead to the bond wire between the swg and motor, no volts.
The voltage is definitely on the bond wire from the pool so I figure it is picking up the stray ground voltage that is occuring between the neighbor and homeowners poles.

The poco doesn't really want to put on an isolator, so they said they would add extra ground wires up and down the road, but I don't think that is going to fix it. They are going to schedule an outage with the neighbor to see if it goes away. If it does, then it will be a case of determining if it is the neighbors issue or their issue between them and the meter.

(The neighbor does have a pond with an under ground wired aeration system - which is between their pole and the swimming pool, so I am wondering if the issue may be with them and not so much the poco).

Since the bond wire has the voltage, I guess I am just wondering why the shock isn't felt all the time since the ladder is in the pool and bonded - and the shock is only felt when the pool bond wire is bonded with the motor/swg bond wire?
Only thing I can guess is since the motor/swg are ground to the panel with the normal 10/2 w ground wiring, and the panel is ground to the normal 8' service ground rod, perhaps the voltage increases as we get a much better ground connection with the stray voltage/neutral issue and I am not detecting that with my volt meter.

 

[danpik]

Maybe I missed it, but, where/when is the shock being felt? Ie...getting out of the pool, sticking a toe in, etc.

Stray voltage can be a difficult thing to nail down. Sometimes there is no real source that con be treaced. This is why everything needs to be bonded to one circuit. This puts everything in the same potential so you don't become the conductor between two different potentials.
Another question...is your pool bond tied to an electrical circuit ground?

 

[JohnT]

My initial thought is that you see the shock when the SWCG/Pump bond wire is in the circuit because they are connected to the panel ground.

When the wires are disconnected, the pool is essentially unbonded. It's probably going to tend to stay at the same potential as the deck, since they are in contact with the same dirt and are touching each other. Even though their connection is poor, with little current they are going to hang around the same potential. That potential could be 5,000V compared to the pump ground, and you wouldn't feel it in the pool because it's the same everywhere in the pool.

When you connect to the pump/SWCG bond wire, you are connecting the pool, ladder and rail (but not the deck) to house panel ground via the pump case, which I'm betting is 1.5V different from the earth around the pool. That means you are moving the pool 1.5V away from the deck, creating the voltage difference that swimmers feel as a shock.

The basis of the problem is probably that panel ground and system neutral at the panel are at a different voltage than earth ground in the area of the pool. I'm still inclined to believe it is the power company grounding practice that is the source of the problem. It might be worth checking the quality of the ground rod at the service entrance. Some areas are known for corrosive soil that damages the conductor over time. Check the connections there and in the box for grounds and neutral.

I THINK we are pretty well on the same page as to what the problems are, but maybe have different theories on the ultimate cause.

 

[notbob]

John. Agreed and makes total sense about the slight difference between the deck/dirt/bond.

Additionally, I had the same thought about the original service ground.
In the box, the neutrals and grounds are good to go as that was the first thing we did.
Also, I drove a new 8' ground approx 10 ft from the original service ground and ran a #6 bond wire between them.
No difference.

I will keep on the poco to see if maybe they can put in an isolator just as a test.
Will update this once they pull the neighbor and see what the results are.



Danpik,
Its felt between the deck and pool when putting a foot, hand in.
Its your standard "bee sting" people describe.
I know it is because the deck is not bonded and there lies 1 issue, but the main issue is looking like stray voltage.
We are going to address the deck not being bonded but want to fix the actual problem as well.

The bond is not connected to any ground rod. The only way it sees "ground" is also what John is saying about the motor/swg being connected to the service ground.
I know alot of people get bonding and grounding confused, but I completely understand that and so there is no physical wire connection from the bonding to a ground rod. (Although as a test, I did connect the bond wire to the service ground just to see if the voltage changed and it did not).

John,
Thanks again for the clarification. I guess even though I rambled on, the big question in my mind was why is it only felt when connected to the motor/swg. That makes total sense that not connected, the deck/earth/bond are relatively close, but connected the voltage is being "moved" away to the service ground via the motor case connection - and creating the more noticeable difference in potential at that point.

 

[jmborchers]

Turing off the main breaker as in the whole house?

You would never feel 1.5V and I'm assuming this is measuring 1.5 VAC. Is there a DC potential in the pool?

In order to feel a shock you would have to be somewhere over 18 VAC/DC. Bee sting seems more descriptive of getting toward lethal voltages >= 48 VAC/DC.

You are measuring 1.5 V between the pool bond and SWG bonding? Wire size is #8?

In order to have 1.5V difference in a #8 wire you need a good amount of current flowing or a significant distance!

 

[JohnT]

Turing off the main breaker as in the whole house?

You would never feel 1.5V and I'm assuming this is measuring 1.5 VAC. Is there a DC potential in the pool?

In order to feel a shock you would have to be somewhere over 18 VAC/DC. Bee sting seems more descriptive of getting toward lethal voltages >= 48 VAC/DC.

You are measuring 1.5 V between the pool bond and SWG bonding? Wire size is #8?

In order to have 1.5V difference in a #8 wire you need a good amount of current flowing or a significant distance!

You can easily feel a 1.5VAC difference or even less when you are wet. Members have reported feeling voltages as low as 0.5V. Generally it is felt in areas where the skin is broken. Check out the threads in this search (assuming it works as a link) search.php?keywords=bonding+deck+shock&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

 

[notbob]

I have read hundreds of posts from here and other sites from the past several years.
Some say you can't feel less than 2 volts and some poco's - even I believe some of the national institutes say less than 2 or 4v stray volts is acceptable but with salt and the swimmer/deck being wet but not bonded, the difference can be significantly reduced.
Cuts/scrapes - shaving legs recently, etc... appear to be where it is felt the most.


The pool is 14x30.
1 #8 wire ran in a loop around entire pool, then probably another 20 ft to equipment pad so a decent amount of #8 in the ground.

The 1.5 is VAC. Turned off the main breaker. Still there.
Had poco disconnect the meter - still there
Poco said they pulled the transformer but I am not exactly sure what they disconnected on that test and I am not positive they lifted the neutral but still there when they did that.

There is .08 dc registering with pool bond wire disconnected from motor/swg and .54 when connected.
However, some posts and other sources say that this can actually be from a salt water reaction of generating the chlorine.
I can't remember exactly what they called it but with that little dc, I am leaning towards the poco/vac end of things as to trying to figure out the dc end of it.

Had phone guys out and physically disconnected service at the pole to test it - still there
Also tried removing phone ground from main poco ground - no difference.

House is on dish tv and digital vhf antenna for local channels.
Disconnected wiring on those - still there.
Drove new 8' ground rod beside the tower.
Tower, dish, antenna all bonded with #6 and connected to that new ground
Also, #6 line ran to main service ground rod from the new one to tie those together.


No underground commercial gas lines or high voltage towers around for miles. (other than a propane tank line buried between tank and house)
No commercial underground or above ground cable tv for a few miles - thus the dish.

We see a 1.5 volt difference between the motor/swg bond wire and pool bond wire when they are not bonded together. When we measure from the ground rod to the motor/swg there is 0 voltage and when we measure from the ground rod to the pool bond wire we get 1.5 volts. There is slight rust/corrosion on the ladder at one bolt and slight corrosion (greening) on the pool bond wire where the swg/motor bond and pool bond were connected. This tells me that obviously there is a potential difference there as well.

Its never been anything of a hard zap, just a light stinging, felt more so on cuts - at the surface of the water at a hand or foot touching the concrete and water. Once more than that is in the pool though, it goes away as I believe the body is coming more to potential with the water and less with the concrete. With shoes on, 1 hand on concrete, 1 hand in water - no shock. That I am sure is due to the shoe/rubber insulating and reducing contact/potential from the body at the water and concrete.

 

[jmborchers]

@JohnT - I researched this further to see where our difference was coming from. The problem is in the measuring device. You can't really use a voltmeter with probes in water to measure the voltage and get a correct result. If you feel the shock, wet with or without salt water etc.. the voltage is much higher than a few volts. I guess this difference between the voltmeter and human likely comes from the exposed surface area to the water.

So with the main breaker off this seems to rule out it's coming from a utility or power line elsewhere. There isn't any separate power meter run to the garage or anything like that is there? Solar cells on the house? I know this is reaching but it seems you've isolated any local power source.

Do you have an ammeter? It's probably only uA current flowing... but might give you more color...

What I'm seeing is you've made your own local ground and also compared service ground. If I'm getting this both your local ground when used and pool bond = 1.5V. Also the house service entrance ground = 1.5V to pool bond?

If this is true and around the pool somewhere in the ground is a >1.5V potential that you can measure why would the difference between the house service ground and your local ground wouldn't also be 1.5V?

Where is you local ground in relation to the other locals you've described as in neighbors pond, electrical entrance?

There's a clue in all of this as to where it's coming from but I can't see it yet.

 

[danpik]

1 #8 wire ran in a loop around entire pool, then probably another 20 ft to equipment pad so a decent amount of #8 in the ground.

Is the pool ladder bonded to this circuit?
You also mentioned a pool bond. Since this is a fiberglas pool I am going to assume that this is nor actually connected to the shell itself.
Is there a water bond? This is usually a stainless plate in a skimmer or a metal skimmer housing. In some newer pools I have seen the waterbond is a brall/stainless fitting in the plumbing that is tied to the bond wire.

We see a 1.5 volt difference between the motor/swg bond wire and pool bond wire when they are not bonded together.

This does not surprise me. In fact I would almost predict you would find a voltage potential between these two

When we measure from the ground rod to the motor/swg there is 0 voltage

Not too surprised here either. Ground rods are not realy designed to conduct small voltages to ground.

and when we measure from the ground rod to the pool bond wire we get 1.5 volts.

This intrigues me. Since both are essentialy in the same potential (assuming the pool bond wire is burried in dirt and not gravel)there should realy be no difference.

There is slight rust/corrosion on the ladder at one bolt and slight corrosion (greening) on the pool bond wire where the swg/motor bond and pool bond were connected. This tells me that obviously there is a potential difference there as well.

Is there a way you could run a wire from the ladder to the rest of the bond system and then test again? I am wondering if there may be enough corrosion in the ladder connection to the concrete to isolate the water and ladder from the circuit.

 

[notbob]

No solar panels, no extra power panels - barn, garage, etc...

The service/panel ground is 1 ft away from the service entrance and about 5 ft away from the motor/swg.
Those are about 20ft away from the pool.

I get the same measurement of 1.5v if I put a probe in the water and 1 on the test ground (8ft from pool) or if I put a probe on the test ground and 1 on the pool bond wire, so the water isn't affecting the reading.
This isn't a permanent ground, just 1 I ran for doing some tests.

I am at the house now and I just tried moving the test ground rod about 60ft from the pool and sunk it 3 ft, but still get the same voltage reading.


Unfortunately no ammeter.

Also, if I measure the voltage from the service ground to the pool bond wire, I get the 1.5 volts.
It is puzzling... but I am leaning towards the stray voltage travelling between the neighbors transformer/pond area across the pool and finding its way to either the house service or transformer. That is why I was hoping to see what a test with a isolator would do or lifting the transformer at the neighbors.
It has been dry here, and the dryer it gets, the more the voltage increases. When it rains hard and the ground gets saturated, it is less, which is along the whole theory about the path of least resistance and dry ground making it easier to travel longer distances.

Danpik,
Pool ladder - both cups are bonded.
As are the handrail's cups.
Verified by continuity test from the handrail to the ladder, the ladder to the bond wire at the connection to the motor.
No bond to the fiberglass pool shell itself.
I did try taking several feet of #6, wrapping it around a stainless pipe and putting it into water, then bonding the other end to the pool bond wire and motor. Essentially doing the water bond in the similar way of the plate or the water bond pipe thingy they sell.
Still get the shock. Actually it feels even slightly more when I do that but I don't notice a voltage increase.

 

[danpik]

Hmmmmm...This is a bit of a puzzle.

Try clamping a wire directly to the ladder and attach it to your bond and see what happens.

Check around the power poles and see if there is any ground rods. Sometimes there are ground rods attached to the transformer centertap. If there are, dump a bucket of water on the ground around them. Dry ground has a lot of resistance This is just thinking out there a bit.

Are you or any of your neighbors having any goofy electrical issues in your house? A loose or disconnected neutral will use the ground as a path back to source (center tap) on the transformer.