Stinging sensation – bonding issue, stray voltage, or something else?

[JamesW]

Builders used to use rebar or steel wire mesh in decks, but now they use fiber reinforced concrete and they think that they don't need the rebar or wire mesh.

Even though you might not need the steel for strength, you need it for bonding.

The other issue is that the NEC allows the use of just a wire loop, which is inadequate.

I will probably need to contact the code committee and tell them to require the steel rebar or steel wire mesh or copper wire mesh in all decks.

In any case, when you have an electrician out, have them do the checks on the neutral for current.

It's really not that hard.

You just clamp around the neutral and see what's what.

You might need 3 clamp ammeters to do the check to see if the 3 wires all add to zero.

The ammeters should be true RMS for best accuracy.

 

[JamesW]

If there is a hot wire putting out current like in the Mike Holt video, the voltage, current, resistance and power can be calculated if you know some of the values.

Ohm’s Law is V = IR, where V = voltage, I = current, and R = resistance.

Power = volts x amps.

For example, the voltage drop from the live wire is known to be 120 volts and the current was measured at 10.35 amps, so that means that the resistance would be 11.59 ohms and the power would be 1,242 watts.

 

[Bugman1401]

Would like to ask a few off the wall questions:
1.) Does OP live near any large transmission power lines?
2.) Does OP live near any underground gas transmission lines they know of?
3.) Does OP receive power service via overhead service wire or UG?
4.) What city does OP live in MI? I can check soil data and typical ground rod length.
More wire in a grid may not help if top soil layer is sandy. May need deeper rods.

 

[newtoPoolsSWG]

Would like to ask a few off the wall questions:
1.) Does OP live near any large transmission power lines?
2.) Does OP live near any underground gas transmission lines they know of?
3.) Does OP receive power service via overhead service wire or UG?
4.) What city does OP live in MI? I can check soil data and typical ground rod length.
More wire in a grid may not help if top soil layer is sandy. May need deeper rods.

1) not that I’m aware of… anything like this would be on the main road outside of the sub.
2) our gas line to the houses is underground, but not aware of the location of any larger transmission lines.
3) electrical service lines are underground and about 30’ from the pool equipment.
4) I live in northern milan. The sub was built on a former farm. The soil has a lot of clay.

 

[Bperry]

Am I the only one crazy enough to suggest getting back in the pool when the electrical inspector is there to demonstrate? Or the skimmer that stung?

 

[newtoPoolsSWG]

Am I the only one crazy enough to suggest getting back in the pool when the electrical inspector is there to demonstrate? Or the skimmer that stu

Unfortunately, it seems like the repeatability is challenging.

@JamesW and others following:
Summary of the inspection today.

A third party came out to assess the pool for any hazards. I was able to have him use his only meter to detect the voltage differences between the pool deck and the water... this morning the difference was up to 1 volt. The mA readings were only showing 0.2 mA which wasn't too concerning to him. He checked the bonding at the ladder, handrail, and each fence post. The ohm reading was less than 1 except for the ladder (which he said was expected as the bond wire was under the concrete). He tested voltage diff between water and pool deck when the pump was off and then flipped on, which showed .5 v change... he said that was the only weird thing that he found.

While they bought his time for a half day, I asked him to test my neutral wire, which I'm not sure was the exact test that JamesW suggested, but the only test he could do as he couldn't touch the power equipment on the outside of the house. He used an ammeter to test the two main lines coming in and the difference was on the neutral. We also shutoff the power and found zero on the neutral.

Fast forward to the end of the convo, the inspector says from his perspective the pool is safe, and he would swim in it. This testing was performed after the SWG was swapped out... we have not swam after the SWG was swapped out.

Is there a pump issue? voltage change when the pump turns on seems strange. Perhaps it was just the SWG? I'm thinking we attempt to swim again and see if anything happens before the final comes back.

 

[JamesW]

He used an ammeter to test the two main lines coming in and the difference was on the neutral.

What were the readings on each line?

We also shutoff the power and found zero on the neutral.

Assuming that the test was done correctly, that is a good result.

 

[newtoPoolsSWG]

What were the readings on each line?

Assuming that the test was done correctly, that is a good result.

I dont' recall the readings he said off hand, but he read the main 1 / main 2 and then the neutral and said it made sense. I told him the concern about current on the neutral, which he basically ruled out.

 

[JamesW]

Ok, not sure what else to check.

Maybe get a good electrician to see what they can find and if they can tell you if doing a full copper mesh deck bond would solve the problem.

 

[JamesW]

He tested voltage diff between water and pool deck when the pump was off and then flipped on, which showed .5 v change

Disconnect the bond wire from the pump and measure for voltage and current between the bond wire and the bond lug on the pump.

 

[newtoPoolsSWG]

Disconnect the bond wire from the pump and measure for voltage and current between the bond wire and the bond lug on the pump.

I disconnected the bond wire. Pump off difference was 0.18v and no current. Pump on diff was 0.22v and no current measured.

The pump switch also turns on the SWG.

 

[newtoPoolsSWG]

Ok, not sure what else to check.

Maybe get a good electrician to see what they can find and if they can tell you if doing a full copper mesh deck bond would solve the problem.

Maybe it was the original SWG that caused the issue? They're on the way to CA for testing. Not sure we'll hear a final report.

 

[JamesW]

I don't think that there is anything that points to any definite cause.

Are people still feeling the shock?

 

[newtoPoolsSWG]

I don't think that there is anything that points to any definite cause.

Are people still feeling the shock?

Sticking your hand in the pool without swimming and feeling a shock has only happened once. Every other time was while swimming. We haven't swam after the SWG was replaced. However, after the third party electric tester came today and stated there are no observable hazards, we plan to swim. Obviously, I would have rather heard "this is an issue fix this."

 

[JamesW]

Fast forward to the end of the convo, the inspector says from his perspective the pool is safe, and he would swim in it.

Ok, hopefully they are correct and the pool is safe to use.

I think that you have been very thorough in checking this out as much as possible.

Of course, make sure to tell everyone to report any feeling of shock.

If someone has a cut or scrape on their hand, that's when they are most likely to feel something.

Test periodically to make sure that there are no elevated voltages anywhere.

I’m not sure what else can be done other than replacing the deck and installing a copper or steel mesh for a better grid.

 

[newtoPoolsSWG]

Ok, hopefully they are correct and the pool is safe to use.

I think that you have been very thorough in checking this out as much as possible.

Of course, make sure to tell everyone to report any feeling of shock.

If someone has a cut or scrape on their hand, that's when they are most likely to feel something.

Test periodically to make sure that there are no elevated voltages anywhere.

I’m not sure what else can be done other than replacing the deck and installing a copper or steel mesh for a better grid.

Again, I appreciate all the guidance throughout the ordeal. It does feel like we've turned over every stone, except the pool deck!

Good to know about the cut/scrape.

I will have the meter ready when we swim the first time and going forward... just in case.

Thanks again! I'll update if anything additional happens.

 

[mas985]

While they bought his time for a half day, I asked him to test my neutral wire, which I'm not sure was the exact test that JamesW suggested, but the only test he could do as he couldn't touch the power equipment on the outside of the house. He used an ammeter to test the two main lines coming in and the difference was on the neutral. We also shutoff the power and found zero on the neutral.

"found zero on the neutral." - Exactly what does that mean? Was that just from the hot leads to the neutral? That would be expected if one cuts off the power (hot wires) but that does not eliminate NEV.

In order to do a proper NEV test, you must test the voltage between the neutral and a distant earth location.

Neutral-to-Earth Voltage (S.32g)

 

[JamesW]

That would be expected if one cuts off the power (hot wires) but that does not eliminate NEV.

Wouldn't you expect some current if there was any significant NEV?

 

[newtoPoolsSWG]

Wouldn't you expect some current if there was any significant NEV?

I get that but the electrician wouldn’t touch the power companies box. So the only way to test is to have the power company do it?

 

[mas985]

Was the neutral current measured? That wasn't clear to me from that statement. If NEV is 2 v and a typical grounding rod as an equivalent resistance of 25 ohms to real ground (NEC max), then the current would be only 80 ma. What was the range setting of the amp meter? Was it an analog or digital meter? Maybe he just didn't have the correct settings to see it.

Anyway a separate voltage test is very easy to do and would confirm if there is or is not NEV. You only have to be about 3 ground rod lengths away from the grounding rod to get 95% of the voltage. It drops off pretty fast with distance. Put a screw driver in the ground and measure the voltage difference between the screw driver shaft and the house neutral/ground.