Equipotential bonding links exposed and extraneous conductive parts, such as water and gas pipes, structural steel and metal ducts, to the main earthing terminal with bonding conductors. During a fault everything bonded rises together, so the voltage between any two metal parts a person could touch stays low even if the whole zone floats above true earth. Main bonding is made at the service entry, and supplementary bonding is added in high-risk areas such as bathrooms, pools and medical rooms.
Main bonding to the gas pipe is missing, the inspector won't sign off until there's a 10 mm2 bond within 600 mm of the meter.
Also heard as
- bonding
- protective equipotential bonding
Do not mix it up with
- Earthing system: Earthing connects metalwork to the ground; bonding connects metal parts to each other.
Related terms
Touch voltage
Voltage a person bridges between a hand on faulted metalwork and their feet or other hand during a fault.
PEN conductor
Single conductor that serves as both the neutral and the protective earth in a TN-C network.
Earthing system
Arrangement describing how a supply's neutral and an installation's exposed metalwork are connected to earth.
Ground loop
Unintended current path formed when connected equipment is earthed at points of different potential.