An Introduction to Essential Electrics: Main Protective & Supplementary Bonding

Vocabulary flashcards covering the key bonding and earthing terms from Module 1, Section 1 Part A of the Domestic Electrical Installer course.

BS 7671

The British Standard that sets the requirements for electrical installations, including bonding and earthing in domestic properties.

Extraneous Conductive Part

Metallic items not forming part of the electrical installation (e.g., gas, water, oil pipes, structural steelwork) that could introduce a potential from outside the installation.

Main Protective Bonding

The connection of all extraneous conductive parts to the Main Earthing Terminal (MET) to minimise dangerous potential differences during a fault.

Main Earthing Terminal (MET)

The common earthing point—usually within or near the consumer unit—where main protective bonding conductors are connected.

Equipotential Bonding

The practice of bonding together exposed metalwork in a dwelling so all parts remain at, or close to, the same electrical potential.

Supplementary Bonding

Additional bonding that links sections of metal pipework (e.g., hot and cold water, gas, central-heating pipes) when continuity is broken by plastic fittings, preventing potential differences locally.

Earth Clamp

A purpose-made device used to attach bonding conductors securely to pipework, providing a low-resistance connection and indicating its safety importance.

Bonding Conductor

A protective conductor used to connect extraneous conductive parts to the MET or to each other for equipotential bonding.

Potential Difference (Voltage) Hazard

The dangerous voltage that can exist between metal parts during a fault if adequate bonding is not in place.

Consumer Unit

The domestic distribution board that houses protective devices and typically encloses the MET for bonding connections.