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Thread: Neutral voltage

  1. #1
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    Neutral voltage

    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?

  2. #2
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    The pool has weak bonding. It should all be at 3 volts.
    BB+/BB=?

  3. #3
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    Ground rods at service will do nothing. The 3 volts is the NEV voltage and would not change with a billion ground rods added.
    BB+/BB=?

  4. #4
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    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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  5. #5
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    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.
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  6. #6
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    Quote Originally Posted by cknight View Post
    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.

  7. #7
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    Quote Originally Posted by Sahib View Post
    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.
    I live for today, I'm just a day behind.

  8. #8
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    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.
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  9. #9
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    Quote Originally Posted by augie47 View Post
    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.
    I live for today, I'm just a day behind.

  10. #10
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    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.

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