Stray Voltage in Pool

J

jhachris

Member
Location
NY
Occupation
Electrical Contractor
Hey guys,

I know this topic has been addressed many times in the forum and I feel I have a good idea of swimming pool equipotential bonding but I wanted to run a scenario I'm dealing with by you guys to see if you could offer any insight and or confirm what I'm thinking.

In ground pool. Probably 30 years old. On the water. One metal ladder and metal one pool light. Client reported tingling in the deep end near the pool light. Checked everything near the pool equipment bonding wise - all good. Pump is GFCI protected. Sure enough I found about 1.5 volts from the metal pool light shell - underwater - to the surface of the water when I stretch my leads as far as they can go (about 3-4 feet). I know you are supposed to drain the pool to test pool light bonding but we haven't gotten that far. I have about .5 volts from the metal ladder to the water. The ladder has continuity to the bond wire near the pool equipment. I found the EGC for the light connected to the brass pipe and brass pool light junction box so I disconnected that, ran a dedicated bonding conductor and reconnected everything so that the pool light shell now has continuity to the bond wire - no change. Light on or off - no change. Kill power to pool subpanel and disconnect ground and neutral conductors - no change. Shut the entire property down via 400 amp disconnect - no change and, on the load side of the disconnect with the breaker off I'm getting 27 volts to ground on phase 1 and 17 to ground on phase 2 which I think is strange. Anyway, there's obviously some stray voltage issue in the ground either from the utility or neighbors property that is finding its way to the pool light shell.

The issue I'm having is that Mike says in the pool bonding video that as long as something metal in the pool is bonded then the water is bonded but... at the same time says that if a metal ladder is bonded and the pool shell is not that then there will be voltage entering the pool at a gradient if the ladder becomes energized. Therefore if the ladder is bonded the pool water is not bonded because the pool water resistance is too high. I think based on what I'm finding here is that the pool shell bond (or bond in general) has been compromised because I have a difference of potential between the metal pool light and the water. I don't want to tell the client they have to rip everything up but I realize that might be the case.

I was going to try and experiment with a few things - maybe run a bond wire to a ground rod and stick that in the water in an attempt to bond the water and see if that changes anything. Let me know what you guys would do.
 
1st thing I would do is get rid of the 120V light in the pool and get a low voltage light fed from a transformer, and the transformer GFCI protected.

However, the most important thing would be to get everything intact with the bonding grid. Without being there, I wouldn't know what is missing, but sounds like something is compromised.
 
Little Bill said:
1st thing I would do is get rid of the 120V light in the pool and get a low voltage light fed from a transformer, and the transformer GFCI protected.

However, the most important thing would be to get everything intact with the bonding grid. Without being there, I wouldn't know what is missing, but sounds like something is compromised.
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Understood. But even with the light disconnected we're still getting voltage through the metal niche. I would probably recommend a low voltage non metallic light if they are going to replace it. But then I still have .5 from the ladder
 
jhachris said:
Understood. But even with the light disconnected we're still getting voltage through the metal niche. I would probably recommend a low voltage non metallic light if they are going to replace it. But then I still have .5 from the ladder
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My recommendation for the low voltage light was not to solve current problem. It was just a safety suggestion.
With that said, even if the problem was the light, there is a break in the EB or the shock would not be felt.
These things are difficult and may require some demo to resolve.
One thing to try is to get a water bond that goes in the plumbing near the pump.
 
Little Bill said:
My recommendation for the low voltage light was not to solve current problem. It was just a safety suggestion.
With that said, even if the problem was the light, there is a break in the EB or the shock would not be felt.
These things are difficult and may require some demo to resolve.
One thing to try is to get a water bond that goes in the plumbing near the pump.
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Alight thanks for the suggestion. Maybe I'll recommend that first as it should be done anyway. But yea I agree I think they have to face facts and consider rehabbing the pool deck sooner rather than later. You're referring to a perma-cast device correct?
 
jhachris said:
Alight thanks for the suggestion. Maybe I'll recommend that first as it should be done anyway. But yea I agree I think they have to face facts and consider rehabbing the pool deck sooner rather than later. You're referring to a perma-cast device correct?
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I believe so. I know it goes in the plumbing line and has a lug through the top where you run a jumper to the bond wire to the pump.
 
Have you watched Mikes videos on "neutral earth voltage" ?
I had to watch them a couple of times to truly wrap my head around what is happening. This pool either never had an equipotential bonding grid or it has been compromised by corrosion.
 
acrwc10 said:
This pool either never had an equipotential bonding grid or it has been compromised by corrosion.
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Was basically my thoughts after reading the OP.

Most of the pool is sitting there at or very near "earth potential". But the bonding conductors that have been fairly confirmed for the ladder and the light are ultimately at same potential as the grounded service conductor as that really is the only connections that was confirmed. There needs to be low resistance between all components, including the equipotential bonding grid or it will be easy to have voltages between components.
 
acrwc10 said:
Have you watched Mikes videos on "neutral earth voltage" ?
I had to watch them a couple of times to truly wrap my head around what is happening. This pool either never had an equipotential bonding grid or it has been compromised by corrosion.
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Yes I have. I'm planning on doing those tests tomorrow or Monday to confirm what we're thinking.
 
kwired said:
Was basically my thoughts after reading the OP.

Most of the pool is sitting there at or very near "earth potential". But the bonding conductors that have been fairly confirmed for the ladder and the light are ultimately at same potential as the grounded service conductor as that really is the only connections that was confirmed. There needs to be low resistance between all components, including the equipotential bonding grid or it will be easy to have voltages between components.
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They're the same potential as the bonding conductor coming out of the ground at the pool equipment. I did not test resistance between that bond and the grounded service conductor.
 
jhachris said:
They're the same potential as the bonding conductor coming out of the ground at the pool equipment. I did not test resistance between that bond and the grounded service conductor.
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But is the rest of the EPB system connected to this, presuming there is one and it is not deteriorated. Deterioration could leave holes in the pool that can be subject to voltage variances.
jhachris said:
Does bonding the pool shell automatically bond the water?
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Yes and no. Water tends to take on potential of the shell, or capacitive effects makes it take on potential of the earth behind a non conductive shell. Concrete needs bonding grid within it if you want to make it take on same potential as everything else that is bonded to said grid. No bonding grid it will take on mostly the same potential as earth it sits on/in which EGC's of pool equipment may not be at earth potential - this sort of situation is where gradients commonly come from.

Earth potential is great, but electrical systems and current flowing on neutral conductors cause rise in potential on any grounded conductor that gets extended to the pool area. Is critical to bond all conductive objects together in the pool vicinity to keep all them at same potential. small non fixed items usually not a problem they don't normally have a path to an area of different potential.
 
kwired said:
But is the rest of the EPB system connected to this, presuming there is one and it is not deteriorated. Deterioration could leave holes in the pool that can be subject to voltage variances.

Yes and no. Water tends to take on potential of the shell, or capacitive effects makes it take on potential of the earth behind a non conductive shell. Concrete needs bonding grid within it if you want to make it take on same potential as everything else that is bonded to said grid. No bonding grid it will take on mostly the same potential as earth it sits on/in which EGC's of pool equipment may not be at earth potential - this sort of situation is where gradients commonly come from.

Earth potential is great, but electrical systems and current flowing on neutral conductors cause rise in potential on any grounded conductor that gets extended to the pool area. Is critical to bond all conductive objects together in the pool vicinity to keep all them at same potential. small non fixed items usually not a problem they don't normally have a path to an area of different potential.
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The only things I know are connected to the EPB are the light, the ladder and the pool equipment. I can't test anything else. The NEV voltage test should tell me more, at least I hope it does.
 
Thank you guys for the feedback. I'll keep you posted as I do further testing as this is just the beginning. Even if the utility fixes the stray voltage issue, I'm going to notify the homeowner that the pool is technically not safe and will need a complete overhaul.
 
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