A path to the earth versus equalizing

The difference between bonding and grounding is one of the misunderstood topics in electrical wiring, and it doesn’t help that the two words are often used interchangeably, only increasing the confusion. But from a safety perspective, it’s important for pool service techs to know the difference and to be sure that both elements are present on the pools serviced. It saves lives.

Grounding

Grounding an electrical wiring system provides a low resistance path to the earth in case the electricity escapes the wiring system by accident.

In a standard electric wiring system, one wire is charged, or hot, while the other is neutral. This difference in charge provides power to devices, as the flow of negative electrons is “pulled” or attracted toward the neutral wire. However, if the wire becomes broken or if a piece of electronic equipment malfunctions, it can create a short circuit, where the electrical current flows through a shorter, and unintended pathway, instead of following the circuit. It does this because, as is the case with so many things, electricity will follow the path of least resistance.

A long path for electricity to flow back to ground is provided by a circuit. When a shorter path is provided, electricity naturally seeks this route, immediately changing its course by an easier, shorter path.

There are two types of short circuits: A normal short circuit and a ground-fault short circuit.

In a normal short circuit, the hot wire carrying the current touches the neutral wire. Resistance goes down instantly and a large current flows through an unexpected pathway.

In a ground-fault short circuit, the hot wire carrying the current comes into contact with some grounded portion of the system.

Thus, anything that can cause the hot wire to come into contact with the neutral wire or the hot wire to come into contact with a grounded portion of the system can cause a short circuit.

Short circuits are caused by:

• Pests chewing through wires can allow the hot wire to touch the neutral or hot to touch grounded metal surfaces.

• Water or liquids coming into contact with electrical wiring can conduct electricity, allowing it to flow to ground, possibly starting a fire.

• Loose connections in an electrical box.

• Old, damaged outlets, switches, lights, appliances, or other electrical devices.

• Nails or screws piercing through walls and coming into contact with wires.

• Damaged or deteriorated wire.

• Buildup or surges of electricity. Intentionally grounding an electrical system solves the problem of short circuits because it provides the electricity a low resistance path to the earth, usually via a piece of bare copper wire. This allows electricity to dissipate, preventing shocks and keeping people safe.

In a swimming pool electrical system, this involves running a grounding wire from the pool equipment back to the breaker panel. If electricity should escape the system by way of a fault, the current will travel to ground, causing a breaker to trip when the fault is detected.

Another way to ground pool equipment is through the use of Ground Fault Circuit Interrupter (GFCI) outlets. These outlets detect when electrical equipment is drawing too much power during a short or fault, and cut power to the shorting device by providing a safe ground path for the electricity.

The electrical equipment for swimming pools must be grounded and connected by wiring methods in accordance with the NFPA 70 National Electric Code (NEC ). The following must be grounded:

• All electrical equipment associated with the circulation system.

Image credit: Electrictechnology.org • All electrical equipment located within 5 feet of the inside wall of the pool water.

• All through-wall lighting assemblies and underwater luminaires.

• Panelboards that supply electricity to equipment associated with the pool.

• GFCIs.

• Transformer and power supply enclosures.

• Junction boxes.

• Pool motors.

Bonding

Unlike grounding, bonding work is generally done only around water features, like pools and hot tubs. It is essential for keeping bathers safe around water.

Bonding, also known as equipotential bonding, is a process of equalizing the voltage potential across all electrical equipment, metal surfaces, and the water itself.It is not the same concept as grounding.

Bonding is joining metallic parts together to create an electrically conductive path that will result in electrical continuity between components, ensuring that the electrical potential will be the same throughout.

Keeping the electrical potential at the same level reduces the dangers created by stray currents in the pool or in the ground around the pool and provide a low impedance path for fault current back to the source circuit to trip an over-current device. Connecting (or bonding) everything metallic in and around the pool will help eliminate voltage gradients (or differences in electrical potential) from one part of the pool to another and from metallic equipment to the pool water.

Bonding is achieved by connecting components together in a loop by using conductors of at least 8 AWG or larger solid copper.

The following is a general list of the items that require equipotential bonding:

• Conductive pool shells, including poured concrete, sprayed concrete, and concrete block with painted or plastered coatings.

• The pool water itself, which can be bonded with a metal ladder added to the bonding grid.

• Structural reinforcing steel, copper conductor grid, or reinforcement metal (rebar) of the pool, spa, coping, shell, framing, etc.

• Perimeter surfaces that extend 3 feet horizontally beyond the inside walls of the pool, spa, or hot tub. A perimeter surface that extends less than 3 feet and is separated from the pool by a barrier require equipotential bonding on the pool side of the barrier.

Bonding to perimeter surfaces must be provided and be attached to the pool, spa, and hot tub reinforcing steel or copper conductor grid at a minimum of four points around the pool, spa, or hot tub.

• All metallic parts of the pool and spa, all fixed metal parts, metal cables and raceways, metal piping, and shells and mounting brackets of pool lighting.

• Underwater lighting.

• All electrical equipment, electrical devices, and controls.

• Water heaters rated at more than 50 amperes.