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Checking Equipotential Bonding Part 2

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    Checking Equipotential Bonding Part 2

    If you haven't seen this thread
    http://forums.mikeholt.com/showthread.php?t=177375

    you might want to look at it before reading this one to know what I'm talking about.

    Customer was complaining of feeling a shock when exiting the pool while holding the handrail.
    So I went to check the bonding around the pool and pool equipment. Here is what I found.

    I had a "neutral to earth voltage" (NEV) of 1.45V
    I had the same (very near) voltage at the pump motor, heater, salt generator, & timer

    At the pool I had practically the same voltage in the water.
    Same at the ladder
    But at the handrail I only had .7V
    So I checked from the water to the rail and got around .7V
    That is where they were feeling the shock, so I figure they were getting from 1/2V - .7V. That checks with the difference in the NEV from everything else and the rail.

    I did show some continuity to the rail but it was a higher resistance than every other item bonded.

    To confirm this I connected a coil of #8 copper (about 15') to the rail and dropped the remainder of the coil into the pool. I checked the voltage again at the rail and it brought it back up to the level of everything else.

    I suspect either loose connection in the cups or deterioration. Customer said that the pool company said they had some way of replacing the mounts/cups at the rail. But he is not going to have them do it until they replace his liner next year.
    I told him the only thing I knew of was to bond the rail to the water the way I did but with something a little neater. Told him to keep that bonded until the rail mounts are replaced and he agreed.

    Anything else I should have done?
    [COLOR=navy]If you aim at nothing, you will hit it every time![/COLOR]

    #2
    Bump
    [COLOR=navy]If you aim at nothing, you will hit it every time![/COLOR]

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      #3
      Nothing?
      [COLOR=navy]If you aim at nothing, you will hit it every time![/COLOR]

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        #4
        I would look for the reason that the voltage is different at the handrail.
        You are looking at earth-neutral voltage but do not know what the potential is to remote earth.
        The handrail is not at a different voltage because of a poor connection. It is at a different voltage either because it is connected to local earth and local earth is at a different potential from the equipotential grid OR it is connected, however weakly, to another voltage/current source.
        The water bond is not sufficient in either theory or code to make it part of the equipotential grid.
        It needs to be metallically bonded to other metal in the grid, even it that requires a shallow saw cut in the concrete to provide the path.

        Comment


          #5
          Originally posted by GoldDigger View Post
          I would look for the reason that the voltage is different at the handrail.
          You are looking at earth-neutral voltage but do not know what the potential is to remote earth.
          The handrail is not at a different voltage because of a poor connection. It is at a different voltage either because it is connected to local earth and local earth is at a different potential from the equipotential grid OR it is connected, however weakly, to another voltage/current source.
          The water bond is not sufficient in either theory or code to make it part of the equipotential grid.
          It needs to be metallically bonded to other metal in the grid, even it that requires a shallow saw cut in the concrete to provide the path.
          It is the potential to remote earth. I checked both to the service from 50' away and at 50' from start of pool equipment. All is the same except the handrail. The handrail does show continuity from one side to the other (same rail) and to the ladder although it is a higher resistance. That is what led me to believe a poor connection.
          I realize that you bond to the water and not from the water. I did that to see if the voltage would go away when going to the water.

          I don't think I mentioned it but I suggested to the HO that a temp. bond wire be run from an exposed EP bond but he wanted to wait until he has his liner replaced to see if the pool company could fix the rail mount. I guess he thought my "bandaid" was the solution.
          [COLOR=navy]If you aim at nothing, you will hit it every time![/COLOR]

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