NEV voltage and pool bonding

[Becker Electric]

When checking the NEV of a pool perimeter, how much variance of Nev is ok between my reading at the service supply panel and the pool permiter. ( for example if Nev at main panel is reading .24 volts and the NEV is reading is different at perimeter lets say .38 volts at the pool perimeter is that too much variance and is a good indicator the permiter is not bonded? Essentially what variance is Ok to allow to confirm bonding.

 

[W@ttson]

When checking the NEV of a pool perimeter, how much variance of Nev is ok between my reading at the service supply panel and the pool permiter. ( for example if Nev at main panel is reading .24 volts and the NEV is reading is different at perimeter lets say .38 volts at the pool perimeter is that too much variance and is a good indicator the permiter is not bonded? Essentially what variance is Ok to allow to confirm bonding.

So this reminds me kind of when Faraday did his experiments to prove that magnetism and electricity were connected. He had a coil and a magnet. He then moved the magnet through the coil and went to the other room to see if he can measure the result. By the time he got to the other room he could not see any effect. The effect can only be witnessed during the motion of moving the magnet in and out through the coil.

It could be very much the case that you measured at the service entrance and got X NEV, then by the time you walked to the pool perimeter you measured Y NEV because loads in the neighborhood changed.

NEV is ever changing and determined by loads outside of the premises. You can have your main breaker off at the house and still have a NEV.

 

[don_resqcapt19]

In my opinion there should be no variance, but that assumes no system load changes between the time you read the voltage at the supply and the time you read it at the pool.
There is no standard as to what may be acceptable.
I would look at doing it with two meters at the same time. One connected to between the service GEC and the remote electrode, and the other connected between the pool equipment and the remote electrode. Readings taken at the same time should be within a few hundreds of a volt of each other, assuming your meter has that good of resolution.

 

[Rjryan]

www.mikeholt.com/pools
There is a PDF that accompanies the video
In that video Mike shows that the Neutral-to Earth Voltage changes with the feeding transformer load.
In the video he shows that it does vary and there is no standard for what is acceptable or normal.

 

[Rjryan]

From a Common origin point the Neutral-to Earth Voltage should be very close at all points of the pool and no voltage reading between the bonded points of the pool to each other.