Purpose of ground wire around above ground pool

[slc410]

I'm curious as to what is the purpose of installing the required solid #8 awg wire 6 inches deep around the perimeter of an above ground pool. Is it to protect people from the potential shock of wet surfaces that occur from water splashing out of the pool ?

 

[jusme123]

It’s part of the pools equipotential bonding , its required to reduce voltage gradients around a pool. See 680.26

 

[kwired]

Equipotential bonding - which the purpose of is to bring things to the same potential.

Many get confused what this is all about and think it is part of "grounding" but it is not.

We commonly utilize the grounded service conductor to carry current - if you have current on a conductor you will have voltage drop on that conductor. Maybe not much but there will be some. POCO's commonly also use the grounded neutral of their primary side of distribution to carry current, and it gets bonded to the secondary grounded conductor. So any voltage drop on primary or secondary imposes a little bit of voltage (relative to earth) on all the grounding conductors that we tie to the grounded conductor back at the service. This may only be a couple volts or so but is enough to be a big problem for people that are immersed into pool of water when they are at same potential as the EGC that attaches to any pool equipment (particularly a pump at very least in nearly all cases) and they happen to contact some isolated object that is at true earth potential. This is why we bond everything in and around the pool as a general rule - to bring all objects a user can contact to the same potential. Then it doesn't matter if the voltage to true earth is 2 volts or a thousand volts, it is zero potential between objects the user can contact at the same time because of the equipotential bonding. There can be voltage gradient near the outside border of the equipotential bonding zone, but that is supposed to be far enough away from the pool a pool user can't touch differing potential simultanously.

 

[don_resqcapt19]

There are many things that can provided voltages in the earth and on metallic parts of pool equipment. If you are in the water and touching something with a potential difference as low as 6 volts, you can be incapacitated to the point that may result in what is know as electric shock drowning (ESD).
The purpose of the perimeter bonding is to eliminate any potential differences between the water and anything you can touch in the pool area.

 

[LarryFine]

Looking up "step potential" can explain a lot, too.

 

[kwired]

Looking up "step potential" can explain a lot, too.

I don't know that a single conductor buried around perimeter of an above ground pool is necessarily sufficient should there be somewhat excessive voltage drop on your service grounded conductor, but it probably is fairly effective for most typical situations.

 

[don_resqcapt19]

I don't know that a single conductor buried around perimeter of an above ground pool is necessarily sufficient should there be somewhat excessive voltage drop on your service grounded conductor, but it probably is fairly effective for most typical situations.

I was listening in on a CMP 17 task group meeting today, and part of the discussion was about the effectiveness of the single ring wire for perimeter bonding, and the comments were, with a bonding system compliant with 680.26, there have been no reported incidents involving a shock between the bonded pool water or equipment and the surrounding deck. There have been a number of cases of injury and even death where the perimeter bonding had not been installed.

That being said, if there was some kind of event that caused a high current to flow though the bonding system there could be excessive voltage drop across the bonding system creating a shock potential.

I don't think elevated voltage, without current is a real problem. Mike Holt has a video of him in an energized pool, and even with 100,000 ohm resistor in the bonding conductor to some of the parts there was not a touch potential between the parts.
Take a look at about one hour and 30 minutes into this video that Mike did:
www.mikeholt.com/pools

Note that I am not aware of what type of bonding system was used in the pool in the video.

 

[kwired]

I was listening in on a CMP 17 task group meeting today, and part of the discussion was about the effectiveness of the single ring wire for perimeter bonding, and the comments were, with a bonding system compliant with 680.26, there have been no reported incidents involving a shock between the bonded pool water or equipment and the surrounding deck. There have been a number of cases of injury and even death where the perimeter bonding had not been installed.

That being said, if there was some kind of event that caused a high current to flow though the bonding system there could be excessive voltage drop across the bonding system creating a shock potential.

I don't think elevated voltage, without current is a real problem. Mike Holt has a video of him in an energized pool, and even with 100,000 ohm resistor in the bonding conductor to some of the parts there was not a touch potential between the parts.
Take a look at about one hour and 30 minutes into this video that Mike did:
www.mikeholt.com/pools

Note that I am not aware of what type of bonding system was used in the pool in the video.

Most the time yes there is no issues. But a single bonding wire around the perimeter could result in reasonably high volts across points a person could contact simultaneously. But you are more likely to be able to stand far enough away from that ring yet reach into pool with your hand and touch those higher potential points. Where if you were actually in the pool (and better bonded to the water in most cases) you probably can't reach outside of the pool all that far and probably won't be as much potential on you.

 

[petersonra]

I'm curious as to what is the purpose of installing the required solid #8 awg wire 6 inches deep around the perimeter of an above ground pool. Is it to protect people from the potential shock of wet surfaces that occur from water splashing out of the pool ?

The purpose is to meet code requirements. beyond that I'm not sure it really does all that much that you couldn't accomplish in a much easier and cheaper way.

 

[Little Bill]

I was listening in on a CMP 17 task group meeting today, and part of the discussion was about the effectiveness of the single ring wire for perimeter bonding, and the comments were, with a bonding system compliant with 680.26, there have been no reported incidents involving a shock between the bonded pool water or equipment and the surrounding deck. There have been a number of cases of injury and even death where the perimeter bonding had not been installed.

That being said, if there was some kind of event that caused a high current to flow though the bonding system there could be excessive voltage drop across the bonding system creating a shock potential.

I don't think elevated voltage, without current is a real problem. Mike Holt has a video of him in an energized pool, and even with 100,000 ohm resistor in the bonding conductor to some of the parts there was not a touch potential between the parts.
Take a look at about one hour and 30 minutes into this video that Mike did:
www.mikeholt.com/pools

Note that I am not aware of what type of bonding system was used in the pool in the video.

He had a grid placed and tied to the rebar during install.