‘WIRED FOR SUCCESS’
Equal Potential and Bonding By Reuben Clark
A homeowner having a pool built recently commented that they keep hearing about “equipotential” and “same potential voltage” and “equipotential bonding.” They said they are not an electrician, and they don’t understand what it all means. Also, why do the steel rebar guys and the electricians and even the pool salesman talk about it for their pool?
They were told that all metallic objects close to the water needed to be “bonded” to put everything on “equal potential.” That somewhat frightened them. In addition to not understanding the issue, they said that if everything is bonded, when “excess voltage” hits one component, it will “electrify” the entire pool. Wouldn’t that shock people in the water and on the deck? To them, it seemed that bonding everything would ensure everyone gets shocked or even electrocuted.
I commented that a colleague explained the situation in a way I feel is easy to understand. Think of the entire pool system as one plane or very large solid surface. This surface (the pool system) is floating in the air. It does not matter how high the surface rises in the air, as long as you are standing on the surface, you won’t get hurt, even if it is one hundred feet in the air. However, if it is one hundred feet in the air, when you step off and try to put one foot on the ground and keep one on the surface, you will actually fall and get hurt. The “potential” energy in this instance is your weight multiplied by the height multiplied by the acceleration due to gravity, and it could be fatal.
Bonding all the objects around the water creates this metaphorical plane or solid surface, and the number eight bond wire is run from the pool system typically back to the pump motor. The pump is bonded back to the breaker panel and bonded to the utility system neutral. Therefore, whatever voltage is on the utility system neutral is the voltage on the pool system, but as long as you stay on that “surface” you are fine.
The 2023 National Electrical Code requires a proper equipotential plane around the body of water and the first three feet of the perimeter surface. This is because the first three feet are the wettest. The deck is designed and intended to get wet. Wet concrete or pavers are conductive, so the further out you measure from the pool, the less wet and less conductive the deck becomes. Think of this decreasing degree of wetness, as a ramp from that solid surface floating in the air, to the ground around it. Without proper equipotential bonding, an unbonded object would create a “hole” in this “surface” and result in a potential hazard.
