Earthing
Connecting an installation's exposed metalwork to earth and back to the supply source. That gives fault a deliberate low- path home, turning a live casing into a large, brief fault current that the protective device can detect and disconnect — without it, the casing simply stays live.
Where Earthing fits in the learning path
The Installation section covers these units:
- Wiring Systems & Enclosures
- Cable Selection & Circuit Design
- Earthing, Bonding & Consumer Units
Curriculum mapping: C&G 2365 Units 203/204/305.
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- Earthing & BondingInstallation
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The earth wire of a circuit. It links the metal parts of the equipment the circuit feeds back to the main earthing terminal. Normally it carries no current; if a fault makes that metalwork live, it carries the fault current so the fuse or breaker switches off. In UK wiring it is green and yellow, or bare inside twin-and-earth cable, with green-and-yellow sleeving wherever it is exposed.
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CPC — Circuit Protective Conductor
The earth wire of a circuit. It links the metal parts of the equipment the circuit feeds back to the main earthing terminal. Normally it carries no current; if a fault makes that metalwork live, it carries the fault current so the fuse or breaker switches off. In UK wiring it is green and yellow, or bare inside twin-and-earth cable, with green-and-yellow sleeving wherever it is exposed.
Read the CPC entryADS — Automatic Disconnection of Supply
The standard protective measure in UK installations: earthing, protective bonding and a protective device working together so that a fault to earth causes disconnection within a prescribed time. If any leg fails — poor earth path, missing bond, wrong device — the fault can sit live on touchable metalwork instead of clearing.
Read the ADS entryMain protective bonding
Conductors connecting incoming metallic services — water, gas, oil, structural steel — to the main earthing terminal. Bonding does not clear faults; it holds the touchable metalwork of a building at roughly the same potential while a fault lasts, so a person touching a pipe and an appliance at the same moment isn't bridging a dangerous voltage difference.
Read the Main protective bonding entryA definition is a start. Using it in a real question is where it sticks.