Got a call for a pool shocking. Checked all bonding using continuity first then did a neutral to earth voltage test. Pool water .5 volts. Concrete 3 volts, hand rail 3 volts, heater , pump and at ground rod 3 volts. (Fiberglass pool). So different potential with pool water and concrete. Pool plumbing also has 2 water bonding fittings plumbed in line and bonded to grid. This is all on the west side of the pool. East side of the pool has only .5 volts on concrete and in earth. This is all present with main breaker to the house off. When I disconnect the bond wire and ground rod all voltage at pool is equal at .5 volts. But I still have the 3 volts on the neutral at the main panel. Re connect grounds and 3 volts back again at pool concrete. Installed 2 new ground rods at service and no changes. Any thoughts?
Neutral voltage
- Thread starter cknight
- Start date
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kwired
Electron manager
- Location
- NE Nebraska
I agree with Mivey. Incoming service neutral is 3 volts to ground. Chances are you are not going to do anything about that. Might be a issue on secondary of your service transformer, might be an issue caused by primary neutral current and is a couple miles to the point where that problem exists.
Proper equipotential bonding shouldn't matter if you have 100 volts on the service neutral - everything within the pool area should be at same potential if done properly. If such condition existed the entire pool would have an elevated voltage above ground, but no gradients within the pool and surrounding deck and other pool related items in this area.
Proper equipotential bonding shouldn't matter if you have 100 volts on the service neutral - everything within the pool area should be at same potential if done properly. If such condition existed the entire pool would have an elevated voltage above ground, but no gradients within the pool and surrounding deck and other pool related items in this area.
Stray current returning via your ground rod to source is the problem. So I think if, instead of ground rod, you use some other code approved, distributed earth electrode such as building steel structure, the problem may be solved.
kwired
Electron manager
- Location
- NE Nebraska
That might be why there is elevated voltage but isn't exactly a problem to NEC , and a reason why NEC requires equipotential bonding around the pool. That entire pool can be 1000 volts above ground potential - but if everything is bonded as it should be in the pool area then users of the pool are like a bird sitting on a high voltage line - nothing they can touch is at a different potential then they are.
kwired
Electron manager
- Location
- NE Nebraska
~3 volts is starting to get to be enough to be concerned enough to address the issue. But it still shouldn't impact the safety of a properly bonded pool installation. This is something that is expected to happen at times and is a reason for all that required bonding associated with a pool.
kwired: In OP case, he apparently checked all bonding. The problem disappears when he disconnects gec. It shows that a reduction of stray current returning ( via gec ) to source solves the problem. So the question is what the minimum requirement is that the effectiveness of pool bonding does not depend on the magnitude of stray current.
Thinking over my own question, I come to the conclusion based on function of Faraday cage though seemingly unrelated here that if number of parralel paths to current path is more, voltage drop per path is less. So if OP finds west side of pool to have higher voltage drops, he may provide additional parallel paths by again interconncting nearby metallic objects around the pool.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
To me a difference of a Volt or two on metal objects indicates either an enormous ground current or a faulty metallic connection between the two (possibly with each connected more closely to local earth ground.
On the other hand, a several volt difference between two points in the water indicates that two different voltage points are (deliberately or inadvertently) bonded to the water in different areas of the pool. That definitely needs to be investigated, since a high voltage gradient in the water can be hazardous regardless of the absolute voltage.
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So there might be a faulty metallic connection between east side (low voltage drop) and west side (high voltage drop). But OP said he checked all bonding for continuity. Perhaps he missed it.
There is no light in the pool. Only a hand rail. The hand rail is on the west side where the higher voltage is present. So there is nothing other than the concrete to check on the east side. I agree that if there is 3 volts on the west side and concrete is properly bonded there should be 3 volts on the east side. But not only is the concrete reading the difference in higher and lower voltage from one side to the other the earth is too. went by today and had 1.9 v between water and concrete. Disconnected bond wire at concrete and everything was back to the same potential. .3 volts
Also contacted power company. No help. They were at this same house one week ago and repaired a burnt underground neutral on the west side of the house. Possibly more knicked wires? That was my original thought of why it would be higher on one side than the other. Closer to the source of the problem. There response was "pool concrete doesn't even have to be bonded. That's a thing of the past. I bet if we pulled the meter the problem would still be there". This is what I have to work with. Not getting anywhere. I also agree if I could get the water to the same potential it wouldn't be an issue. But we have 2 water bonding fittings in there currently. Not sure what more I can do. I feel like we're trying to put unwanted voltage into the pool. Just still think I'm missing something. Not the usual pool shock situation I see.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
It sure sounds like there is a problem with the POCO distribution neutral.
Do it and see whether it is really so. In fact, the purpose of all bonding around the pool is to make current entry into pool water negligible under all design conditions.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Or perhaps a neighbor's service neutral is failing, and raising the voltage on his neutral via the water pipe bond.
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