Neutral voltage

cknight

Member
Location
manteo NC
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?
 

mivey

Senior Member
Ground rods at service will do nothing. The 3 volts is the NEV voltage and would not change with a billion ground rods added.
 

nickelec

Senior Member
Location
US
Try to temporarily connect a wire from the hand rail to water if the voltage goes down to 3 then you know you have a bad water bond

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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.
 

Sahib

Senior Member
Location
India
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?
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
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.
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.
 

augie47

Moderator
Staff member
Location
Tennessee
Since the voltages are there with the house power off, contact POCO. As mentioned by kwired, the problem may not be close by but there are often measures they can take to reduce the potential.
 

kwired

Electron manager
Location
NE Nebraska
Since the voltages are there with the house power off, contact POCO. As mentioned by kwired, the problem may not be close by but there are often measures they can take to reduce the potential.
~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.
 

Sahib

Senior Member
Location
India
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.
 

Sahib

Senior Member
Location
India
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.
 

GoldDigger

Moderator
Staff member
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.
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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Sahib

Senior Member
Location
India
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.
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.
 

cknight

Member
Location
manteo NC
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
 

cknight

Member
Location
manteo NC
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.
 

Sahib

Senior Member
Location
India
Tracing the origin of stray current and setting it right is the best remedy. If that is not readily doable, a flat metal strip loop may be laid around the pool bonding the hand rail, West and East sides etc together.
 

cknight

Member
Location
manteo NC
Yes that will get all the concrete to the same potential but not the water. Why the voltage when the bond is connected but not when it is disconnected? Seems the voltage would still be present in the concrete if it was ground voltage.
 

Sahib

Senior Member
Location
India
Yes that will get all the concrete to the same potential but not the water. Why the voltage when the bond is connected but not when it is disconnected? Seems the voltage would still be present in the concrete if it was ground voltage.
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.
 
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