Stray voltage around swimming pools

[bigdee]

Has anyone noticed getting electrical shocks when getting out of thier pools? I have found this to be an unpleasant situation in a number of pools in my area. If you are standing in the pool and reach out and touch the concrete it feels like a bee sting. I had the same problem with my pool,some days were worse than others so I done a little investigating and what I found was literaly shocking. The NEC requires that the pool's bonding grid (coping,ladders,pump,and all metal objects within 5 feet of pool be connected to the home's electrical ground. The problem with this is the utility company ties the CENTER tap of thier transformers to the same ground. The center tap on the secondary side is sometimes also bonded to the same ground. What does this mean......it means that 13k GROUNDED volts is tied directly to your pool!!! Due to voltage gradients between the service ground and the pool's ground there will be,instead of 0 volts, a voltage potential (in my case 2.1 volts). I removed the pool bond from the electrical service altogther and the problem went away. Everything is still bonded together and protected by a GFCI so there is not a safety issue but is a violation of the NEC code. Ok all you electrical engineers let address this problem to the NEC......thare has been at least one death contributed to this.

 

[rbh]

Re: Stray voltage around swimming pools

Step potential comes to mind, that would be the water to the concrete, concrete to ground, ground to the transformer or the consectric ground, unless you have a delta system in which there is no consentric ground and it is earth return.

 

[bruceb58]

Re: Stray voltage around swimming pools

Please explain what a concentric ground is.

 

[bigdee]

Re: Stray voltage around swimming pools

Step potential comes to mind, that would be the water to the concrete, concrete to ground, ground to the transformer or the consectric ground, unless you have a delta system in which there is no consentric ground and it is earth return.

Exactly...Stray Current flowing through the earth and through the equipotential plane. I don't know about the transmission lines in BC but in north America the power grid use a 3 wire (grounded neutral) instead of a four wire system to save money.

 

[bruceb58]

Re: Stray voltage around swimming pools

If you are getting a voltage potential of your pool to the house ground, you have an extremely dangerous condition and you aren't really bonded for some reason. What is the voltage potential that you measure when you disconnect the service to your house through the main breaker?

How is your house grounded?

What in the heck do you mean by 13K grounded volts?

I don't know about the transmission lines in BC but in north America the power grid use a 3 wire (grounded neutral) instead of a four wire system to save money.

Not true. You will only have a neutral coming from the transformer that feeds your house.

 

[bigdee]

Re: Stray voltage around swimming pools

Please explain what a concentric ground is.

A grounded conductor as in the neutral wire on U.S. homes......the cheap way out IMO.

 

[bruceb58]

Re: Stray voltage around swimming pools

This almost sounds like there is a neutral fault feeding your house or at your panel. I had a friend with a similar problem and the power company found a corroded neutral on their side of the panel. I would rebond and call the power company.

 

[bigdee]

Re: Stray voltage around swimming pools

If you are getting a voltage potential of your pool to the house ground, you have an extremely dangerous condition and you aren't really bonded for some reason. What is the voltage potential that you measure when you disconnect the service to your house through the main breaker?

How is your house grounded?

What in the heck do you mean by 13K grounded volts?

1otential still exist with meter pulled from service
2:home is grounded by NEC code standards
3: Open all the grounds and get between it and you will see (feel the 13k volts!!) if that is the primary voltage on your transformer

 

[bruceb58]

Re: Stray voltage around swimming pools

The power company can come out and check the potential difference between the ground at your house and the neutral feeding your house to make sure it is zero. That would be my next step.

 

[Fishing Dude too]

Re: Stray voltage around swimming pools

You forgot to say where you are at. Taking been long and dry there. Your houses ground is drying out, need to add moisture, take a 5 gallon bucket and pour on ground rod, then take a 5 gallon bucket with a lid drill a very small hole in bottom, fill with water, put next to ground rod will keep it moist.

 

[bigdee]

Re: Stray voltage around swimming pools

This almost sounds like there is a neutral fault feeding your house or at your panel. I had a friend with a similar problem and the power company found a corroded neutral on their side of the panel. I would rebond and call the power company.

Done that...everything checked out..........had to dig into some electrical theory to find root cause.......This is an application problem that the NEC needs to look into. Google this and you will find this to be a problem in countries that use a grounded conductor for service. The NEC is wrong (IMO) in requiring that pools be tied to the service grounding system. I will not use their standard on MY pool!

 

[bruceb58]

Re: Stray voltage around swimming pools

I wonder what their definition is of an acceptable potential if you still measure 2.1V with the meter removed.

 

[rbh]

Re: Stray voltage around swimming pools

In BC they run either 3 phase or single phase over a consentric neutral (every one on the pole bonds to this neutral through the earth ground #6-8. It goes from the beginning to the end of the run and is tied off to all the primary feeds.
There is an earth ground the first, the last and every 3-4 poles in between.

This is the potential I am talking about to include step potential were there is a better ground either one side or the other of the pole.

In a delta they will only place a neutral between one set of poles for the transformer, great if you have good return in the ground and not rock.

 

[jim765]

Re: Stray voltage around swimming pools

i say they have a hot ground somewhere ,some one doing elect work not knowing what there doing,say at a neighbors home?

 

[jim765]

Re: Stray voltage around swimming pools

also getting feed back on ground.

 

[SS MAYFLOAT]

Re: Stray voltage around swimming pools

I had this problem at the country club I worked at years ago. Some people couldn't feel it but others did. It was very dry that year and the multiple ground rods at the transformers and for the main panel was not giving a true 100% ground. Soaked the area with water with a 5% muratic acid and the problem was corrected. Then the one ground rod that was for the pool lights, we could not get a 100% ground. We pulled the rod and it was only 4' long! Apparently it was hitting a big rock so they cut it off. Moved the new rod over 2' and got all 10' in the ground and corrected the problem.

 

[rbh]

Re: Stray voltage around swimming pools

Exactly...Stray Current flowing through the earth and through the equipotential plane. I don't know about the transmission lines in BC but in north America the power grid use a 3 wire (grounded neutral) instead of a four wire system to save money.

OH, and by the way BC is British Columbia, Canada, Through mainly hydro electric dams we produce between 43.000 and 54.000 gigawatt hours per year, and there are times when we sell many mega watt hour to the pac north west and california (think were still waiting to get paid for that one???)

 

[rbh]

Re: Stray voltage around swimming pools

A couple of things to add
For primary wire- if there is a crack in the porcelain insulator or it is very dirty it will jump the flow or a portion of it to the pole, thus energizing it, the neautral, the tel messenger, drops, portions of the guys unless there is an johnny ball (insulator) in it to stop the flow to the anchor.
and will energize those areas till it is bled back to earth through the grounds.

Guys- if there is not an insulator in any of the down guys you will get induction flowing to ground through the anchor rod, when this happen you get electrolysis and the anchor rod will rot just below ground level, which means when the poles starting to rot "spring", away it goes, nothing to hold it up.

 

[bigdee]

Re: Stray voltage around swimming pools

I had this problem at the country club I worked at years ago. Some people couldn't feel it but others did. It was very dry that year and the multiple ground rods at the transformers and for the main panel was not giving a true 100% ground. Soaked the area with water with a 5% muratic acid and the problem was corrected. Then the one ground rod that was for the pool lights, we could not get a 100% ground. We pulled the rod and it was only 4' long! Apparently it was hitting a big rock so they cut it off. Moved the new rod over 2' and got all 10' in the ground and corrected the problem.

That might correct a seasonal problem but the potential is still there and it does nothing for gradients through the equipotential plane. If the pool is isolated from the service ground this problem cannot exist. In my case I removed the ground wire that feeds the GFCI since all the pool equipment is downstream from that point. The GFCI does not require a ground for it to work as a ground fault interrupter. The pool and all equipment are bonded together and is tied to an INDEPENDENT ground rod.

 

[NSBCraig]

Re: Stray voltage around swimming pools

Wow man! You have a problem not the NEC.

Seriously have the problem checked by a pro.