Pool Bonding - Not so good

[FSI_C-12IP]

:grrrr:
Here's the scoop. When the pool was built, I asked the builder about bonding. They DID NOT use any kind of grid in the concrete decking, just a heavy gauge copper wire around the pool, behind the coping (it's a vinyl-liner pool) and connected to the ladder, hand rail, pool light and diving board. It was a continuous wire that then ran to the pad and pump. They assured me it was properly 'grounded' (his word) by connecting it to a grounding rod they drove into the ground near the pad. Also connected to the same wire was the booster pump and then a line ran up into the timer box/circuit breaker panel for the pool. I knew this was grounding, not bonding, but thought 'they've been doing this a long time, they must know'

Well, guess what? There's a tiny voltage between the water and deck that you can feel (if you have a hang nail or small cut on a finger when you reach into the water while standing on the wet pool deck, for instance). Most times you wouldn't notice, but it's there.

Now what? Can anything be done short of breaking up the deck and doing it over, correctly?

 

[JamesW]

I know of several pools that have the same thing. It's one of the reasons I would always insist on wire mesh or rebar throughout the concrete deck.

There is supposed to be an equipotential bonding grid extending for a minimum of 3 feet into the concrete deck. If the pool was inspected by an inspector, then they should not have passed the electrical without the proper bonding grid.

http://www.dom.com/about/safety/pdf/pool_equi_bond.pdf

 

[FSI_C-12IP]

Yep, it's wrong. No question.

Unfortunately, there was no inspection requirement where we live in Lower Alabama.

So what's my recourse?

Edited to add...

Oops, just noticed your attachment has a section that addresses my recourse/options.

 

[CraigMW]

Is there a small leak in the liner? I thought vinyl or fiberglass pools were exempt from the NEC code section regarding equipotential bonding grids. With a gunite pool, there is enough porosity in the concrete to allow for electrical flow to the bonding grid, but fiberglass or vinyl liners would act as strong insulators and such a bonding grid would be non-functional.

Do you notice the electrical flow if you turn off all electricity going to the equipment pad and/or pool lighting?

 

[JohnT]

Is there a small leak in the liner? I thought vinyl or fiberglass pools were exempt from the NEC code section regarding equipotential bonding grids. With a gunite pool, there is enough porosity in the concrete to allow for electrical flow to the bonding grid, but fiberglass or vinyl liners would act as strong insulators and such a bonding grid would be non-functional.

Do you notice the electrical flow if you turn off all electricity going to the equipment pad and/or pool lighting?

Pool surface doesn't matter. In reality, insulation is bad in this case because it allows a difference in potential to exist.

Your electrical system has three ground connections now: The service ground at the meter/panel, the ground rod on the bonding system, and then probably the wire from the pool timer to the bonding system.

My first step in this case would be to check the connection going into the timer. I assume it's a ground connection, and probably needs to be disconnected. I'd disconnect it and see what effect it has. Next try disconnecting the bond wire from the ground rod and see what it does.

If that doesn't help call your utility and tell them you are having stray voltage issues. You may have to be persistent to talk to somebody technical.

You may also want to have your service connections checked for tightness. A loose neutral can cause some bizarre things to happen in your system.

 

[PoolGuyNJ]

AFAIK, there should not be a ground rod used on the bond wire, per the NEC guidelines. You now have two grounds, each with different electrical potentials. A current may flow between the two. In Canada, the bond wire is connected to the main ground. Not a big deal since all the equipment has a ground line too. The bond can get to the ground of any electrical device, like a pump motor, anyway,

NEC-2008 codes and later require the deck to have a conductive mat, either copper grid mesh or steel rebar, 3' out, regardless of the pool type or deck type. This mat must be attached in multiple places, usually 4 or more points, around the pool.

The only ground should be located neat the entry point of power to the home. If there are long runs, as in hundreds of feet from a sub-panel supplying pool to the main panel, a second rod may be used but the two must be joined with a really beefy conductor so there is only one ground per supply transformer from the power company.

Scott

 

[charlie_nj]

As an alternate method for equipotential bonding, NEC 2008 Sec 680.26 does allow a #8 bare copper wire around the perimeter of the pool 18 to 24" from the wall and 4 to 6" below the finished deck surface. This is an approved alternative to the ridiculously expensive bonding mat or to utilizing the rebar grid as the bonding grid.

The ground rod attached to the bonding grid is not allowed.

Also, 2008 requires that the water be bonded as well, usually done by bonding the metal ladder.

His bonding method sounds like it was fine (except for the ground rod), can't say whether he installed it properly using all the proper direct burial connectors, etc. If you have a light, did he properly bond the light niche?

I agree with calling the power company and telling them you have stray voltage. When you turn off the main breaker for the pool subpanel, is the voltage still there? If you disconnect the grounding rod clamp, is the voltage still there?

 

[JohnT]

The ground rod attached to the bonding grid is not allowed.

NEC doesn't prohibit it. It just says it's not required. "Equipotential bonding is not required to extend to or be attached to any panelboard, service equipment, or grounding electrode."

In Canada a grounding electrode is required.

 

[FSI_C-12IP]

Wow! Lots for me to consider/digest. Thanks, everyone! Keep those comments coming.

 

[JamesW]

Diagnosing this type of problem can be very technically challenging. Most electricians can do the basics, but going beyond that takes special knowledge.

If the problem persists after checking all common issues, you might want to check for harmonic currents. Harmonic Currents can be caused by non-linear loads, which can cause neutral to ground currents.

Types of non-linear loads are electronics, which usually contain a switch mode power supply (AC to DC converter), and 3 phase variable speed drives.

If possible, the power company should check the overall quality of the power supply including checking the sinusoidal waveform of the incoming power and measuring the Total Harmonic Distortion (which should not exceed 10%).

Note: I am not an electrician and I don't have any special expertise in this type of problem. I know that finding someone capable of diagnosing and correcting this issue can be difficult. I know of several pools where the problem has never been fixed and they just live with it.

I think that it's important to be as thorough as possible to try to correct this as any voltage or current in water can be a safety hazard.

After having an electrician verify that the pool is safe to use, you could check if using a bonding grid in the concrete would have helped, by holding onto the ladder (which should be bonded), and then touching the water. If you don't feel the electricity, then the grid would help. If you still feel the electricity, then the grid probably wouldn't help.

Unfortunately, adding a grid after the fact is not easily accomplished.

 

[FSI_C-12IP]

Interesting...

When I turn off the power to the equipment pad at the main breaker(about 30 ft from the pad or so) there's still a voltage that's measurable between the water and the metal ladder and also between the water and the handrail. Maybe more of a stray voltage than anything...

 

[barnyard]

As James W stated, this one might be tricky to pin down. I keep going back to your original post and you said that there was another ground rod installed around the deck and pad. "IF" this ground rod was not properly bonded to your incoming power ground rod, a ground loop current might exist. That 'could' explain the presence of current that you are experieinceing even when you remove the power to your equipment. By saying 'removeing power', exactly what method are you using to do this? You said from the main panel, but are you shutting off just the power to the pad or the main breaker for the whole house? A lot of people think the terms grounded and bonded are interchangeable, when in reality they are 2 totally different things and are used for 2 different applications. It surprises me the number of master electricians that don't have a good grasp on this concept also. I am not a licensed electrician, but have worked high and medium voltage for over 30 years, and have seen more than my fair share of stray current problems.
Quick questions: Does the OP have any high power lines in the vicinity? How about broadcast (TV, Radio) towers nearby? How is the power delivered to your pad? A subpanel that is not installed correctly can induce ground loops if the neutral and grounds were not separated at the sub panel.
I am still thinking this is a ground loop problem either with the extra ground rod or the subpanel. You should try to find an experienced electrical type person to isolate this potential, I don't believe any of us on this forum will be able to isolate your problem without actually being there. You have been given some good info already that might enable you to solve your problem. I'm hoping you won't have to bust up your decking to correct it though.