Stinging sensation – bonding issue, stray voltage, or something else?

[mas985]

Maybe the utility wires are exposed underground.

Power company has breakers on all hot wires. Plus voltage dissipates very quickly through the earth as it is volumetric flow (i.e. infinite conductor).

Maybe the neighbor has a bad neutral and they are sending 10 to 20 amps into the ground.

That current can be picked up by the pool bonding grid where it will flow to the main neutral.

The current will go through the house neutral, which does not go through a breaker.

That is possible but the voltage at the ground point would be much less than 120v because that current has a voltage drop across what ever device is using that current. In addition, a ground rod has about 25 ohms of resistance to distant earth so voltage gradient away from a ground rod is very very steep. Any significant distance away from the ground rod would have zero voltage.

Again, NEV is fairly common in rural areas so to me, it just seems a more likely scenario.

 

[mas985]

Mike Holt has a video where he drops a live wire into a pool and 10.35 amps were flowing into the water without tripping a breaker.

The current traveled through the water to the bonding grid and then to the house main neutral and into the earth.

He tested the voltage differential at several places and found substantial differences as you would expect as the hot is at 120 volts and the neutral is at about zero.

So, it can definitely happen without tripping a breaker.

Most breakers are 15 amps or more, so you can have up to 15 amps on a 15 amp breaker without tripping the breaker.

He changed the video to private, so it’s not available any more.

It was his “How to test a pool bonding grid” video.

Below is a picture of his ammeter on the live wire that he dropped in the pool.

Yes, in that scenario, there would be a current generated. But if he measures the voltage from the bonding grid to distance earth, it will still be very close to zero. Most of the voltage drop is in the water. If he had touched the 120v directly to the bonding wire, it would have likely tripped the circuit breaker.

This is an extreme case that is not very likely.

 

[mas985]

But if the OP disconnects the bonding grid from the house neutral/ground and measures the voltage from the grid to distant earth and from the neutral to distant earth and there is only a voltage difference to the neutral, then it likely an issue of NEV combined with a poor bonding grid.

 

[JamesW]

Power company has breakers on all hot wires.

Really big breakers, so they won't trip at 10 to 20 amps of leaked current.

Again, NEV is fairly common in rural areas so to me, it just seems a more likely scenario.

I agree that NEV is the most likely issue, but I don't think that we can rule out other problems.

NEV is common, so why don't all pools have the same issue?

In my opinion, there is a significant probability of an issue beyond common NEV.

 

[JamesW]

In any case, testing for current on the neutral is fairly easy and it can help diagnose the problem.

 

[mas985]

Really big breakers, so they won't trip at 10 to 20 amps of leaked current.

If the conductor is directly exposed to earth as you originally suggested, it would trip the breaker. If is a small leakage, then by definition, it is not full voltage into the ground and it would not travel far anyway. It would have to be very close to the pool to cause an issue.

I agree that NEV is the most likely issue, but I don't think that we can rule out other problems.

NEV is common, so why don't all pools have the same issue?

Because some are bonded properly so it is a non-issue. Again, if the water and the deck are all at the same potential, no shock would occur since no current would flow.

 

[newtoPoolsSWG]

If the conductor is directly exposed to earth as you originally suggested, it would trip the breaker. If is a small leakage, then by definition, it is not full voltage into the ground and it would not travel far anyway. It would have to be very close to the pool to cause an issue.


Because some are bonded properly so it is a non-issue. Again, if the water and the deck are all at the same potential, no shock would occur since no current would flow.

When the deck is dry I measure a voltage diff from the water to deck. This seems to indicate not an effective bonding grid. The tingling wasn’t experienced until we were wet and the deck was wet. Perhaps there is stray current that is picked up when the deck is wet making the difference potential higher.

Earlier I posted the .59mA between the water and slide screw. Last night it was zero. Seems like that also validates the NEV theory.

Perhaps related? I noticed my neighbors “DIY koi fish pond” made me wonder if he’s properly running all the electrical for his pumps. It’s not a huge pond but it’s closest to that side of my pool deck.

 

[mas985]

When the deck is dry I measure a voltage diff from the water to deck. This seems to indicate not an effective bonding grid. The tingling wasn’t experienced until we were wet and the deck was wet. Perhaps there is stray current that is picked up when the deck is wet making the difference potential higher.

The water makes the concrete more conductive and if the concrete is not bonded, it makes for a better connection to the earth.

Earlier I posted the .59mA between the water and slide screw. Last night it was zero. Seems like that also validates the NEV theory.

My thoughts as well.

Perhaps related? I noticed my neighbors “DIY koi fish pond” made me wonder if he’s properly running all the electrical for his pumps. It’s not a huge pond but it’s closest to that side of my pool deck.

How far away is it? Again, voltage drops very quickly from the entry point into the earth and the smaller the contact area with the earth, the faster the voltage drops. Generally it requires a direct (i.e. low resistant path) source contact for that type of voltage which again, points to NEV.

The biggest issue you will have is how to fix this. Repaving the deck is option albeit an expensive one but there may not be any alternate that is 100% effective.

 

[Poolbreh]

Do you have any construction photos of the deck?

 

[newtoPoolsSWG]

The water makes the concrete more conductive and if the concrete is not bonded, it makes for a better connection to the earth.


My thoughts as well.


How far away is it? Again, voltage drops very quickly from the entry point into the earth and the smaller the contact area with the earth, the faster the voltage drops. Generally it requires a direct (i.e. low resistant path) source contact for that type of voltage which again, points to NEV.

The biggest issue you will have is how to fix this. Repaving the deck is option albeit an expensive one but there may not be any alternate that is 100% effective.

The pond is probably 100’ away. So perhaps unlikely.

 

[newtoPoolsSWG]

Do you have any construction photos of the deck?

I wish I had more clear photos. I have some video but it’s hard to see. From my recollection the concrete crew came and framed the space. The same day the electrician ran the bonding wire connecting the hand rail and ladder (perhaps other points but don’t recall).

Then the concrete guys poured a week later. There was only pea gravel down no rebar or mesh to the best of my recollection.

 

[JamesW]

If the conductor is directly exposed to earth as you originally suggested, it would trip the breaker.

Mike Holt dropped a live wire into a bonded pool and it did not trip.

The current was only 10.35 amps.

The earth is a poor conductor, so it is entirely possible that you would have a lot of current but not enough to trip a big breaker.

The power company breakers will probably be bigger than 200 amps.

In any case, measure for current on the neutral and see if it is what it is supposed to be or not.

 

[JamesW]

Again, NEV is fairly common in rural areas so to me, it just seems a more likely scenario.

Even though other issues are unlikely, it does not mean they are impossible.

What does likely or unlikely mean in terms of probabilities?

1%, 5%, 10%?

The problem with assuming that it is just a defective bonding grid is that you might spend $20,000.00 redoing the deck and bonding grid only to find that it did not solve the problem.

In my opinion, trying to rule out all other possibilities as much as possible before deciding to rip out a deck and install a copper mesh grid and then redoing the deck is a worthwhile thing to do.

 

[mas985]

Even though other issues are unlikely, it does not mean they are impossible.

What does likely or unlikely mean in terms of probabilities?

1%, 5%, 10%?

I never said they were impossible, just improbable. But again, the bond to neutral testing will tell you this.

The problem with assuming that it is just a defective bonding grid is that you might spend $20,000.00 redoing the deck and bonding grid only to find that it did not solve the problem.

I never suggested that. I was only suggesting that there may not be any other solution to a poorly bonded deck than to replace it.

In my opinion, trying to rule out all other possibilities as much as possible before deciding to rip out a deck and install a copper mesh grid and then redoing the deck is a worthwhile thing to do.

No disagreement. Again, that is not what I was suggesting.

 

[JamesW]

@

newtoPoolsSWG, can you ask the builder what was done on the bonding?​

If it fails inspection, they might have to redo it on their own cost.

At a minimum, the electrician who did the work should have an interest in figuring out what the problem is rather than just ignoring it.

It does not look good for them that they just act like failing the inspection is no big deal.

Maybe they can come back and check for current on the neutral.

What is the license classification of the electrician who did the work?

 

[newtoPoolsSWG]

@

newtoPoolsSWG, can you ask the builder what was done on the bonding?​

If it fails inspection, they might have to redo it on their own cost.

At a minimum, the electrician who did the work should have an interest in figuring out what the problem is rather than just ignoring it.

It does not look good for them that they just act like failing the inspection is no big deal.

Maybe they can come back and check for current on the neutral.

What is the license classification of the electrician who did the work?

I will ask the builder what was done on the bonding. We've discussed the possibility of re-doing bonding, and he has said that he'd prefer to just take a saw to the concrete to lay a new bonding wire instead of tear up all the concrete. To me, it seems like the bonding wire (vs including mesh or rebar) is his only approach to bonding (although he subs out the electrical work).

The electrician and builder have been out a couple of times. The first time they tried to repeat the issue (where I was told 1 volt diff was ok by the electrician). The second time was when the SWG/panel were replaced. I suspect they're all hoping it's some easy fix. The electrician was pretty quiet when coming back out. When looking up the electrician on the state website, it just says master electrician. Not sure how to see any further detail on the license.

For both the builder and the electrician, I assume they're both invested in resolving a failed inspection. We are at going into week 3 after initial reported issue... and doesn't feel like we've made significant progress. The builder repeatedly told me he's never seen the issue in the last 20+ years and 300 pools. It's strange to me it's not more common with the approach I saw to bonding - just laying the wire and covering in concrete.

The township inspector has failed the final and will only move forward after a third party comes to check voltages around/on the pool/etc to show 0 voltage difference. The third party comes Monday to do the assessment - I'll be able to articulate more of what they're doing when they come.

 

[JamesW]

A single wire is not going to solve the problem.

You need a copper bonding mesh 3' wide.

3′ WIDE X 100′ LONG COPPER EQUIPOTENTIAL BONDING GRID W/KIT <span> Case Qty. 1</span> - Consolidated Manufacturing

KIT INCLUDES 20 #8 SPLIT BOLTS, 16 METAL STAKES Case Qty. 1 AVAILABLE IN CUSTOM LENGTHS ; 50’. 125’, 150’, ETC.

www.cmiwebsite.com

https://www.greaves-usa.com/wp-content/uploads/pdf/80.pdf

https://www.nespapool.org/Portals/0/Pool%20GroundingE270LT07.pdf

https://www.greaves-usa.com/wp-content/uploads/2015/09/CBM-Product-Sheet-6-17-08.pdf

 

[newtoPoolsSWG]

A single wire is not going to solve the problem.

You need a copper bonding mesh 3' wide.

View attachment 441925


View attachment 441926

3′ WIDE X 100′ LONG COPPER EQUIPOTENTIAL BONDING GRID W/KIT <span> Case Qty. 1</span> - Consolidated Manufacturing

KIT INCLUDES 20 #8 SPLIT BOLTS, 16 METAL STAKES Case Qty. 1 AVAILABLE IN CUSTOM LENGTHS ; 50’. 125’, 150’, ETC.

www.cmiwebsite.com

https://www.greaves-usa.com/wp-content/uploads/pdf/80.pdf

https://www.nespapool.org/Portals/0/Pool%20GroundingE270LT07.pdf

https://www.greaves-usa.com/wp-content/uploads/2015/09/CBM-Product-Sheet-6-17-08.pdf

I found a video after the concrete was framed out. I did a screencap of the area. You can see the bond wire. I’m assuming the mesh would have had to be in place for the electrician to connect to. This validates my memory of the state before pouring happened.

 

[newtoPoolsSWG]

I ran the same test again. The .80 was while pump running and drops to .57 when pump shuts off. Maybe this means the pump is contributing to the issue?

The 3rd pic is where my wife was sitting and the pool water pools on the concrete. I dumped a bucket of water there and ran the tests.. .86mA and the voltage was 1.55

 

[timjs]

I don't feel the pump is the problem. Electricity doesn't take the path of least resistance, it takes every possible path, proportional to the conductivity of each path. Some of that pump current is going to flow in and around the pool bonding system, and therefore voltage drops will be measurable. If there's a voltage drop present, a meter in parallel will shows some current, as it is now one of the many possible paths for the current to flow.