PEN conductor
Protective Earth and Neutral
A single conductor that does two jobs, acting as both neutral and protective earth. You'll meet it in the distributor's cable on a (PME) supply, where it's split into separate neutral and earth at the intake. If it breaks, earthed metalwork can rise to a dangerous , which is why several BS 7671 sections treat PME supplies differently.
Using PEN conductor in context
Reviewed
A distinction worth remembering
Earthing provides a connection used in the fault-protection arrangement. Protective bonding connects relevant conductive parts to reduce dangerous potential differences. The fact that something is metal is not enough to decide whether it is an extraneous-conductive-part.
Questions to take further
- How can I revise PEN conductor beyond the definition?
- Explain what PEN conductor describes, compare it with a related term and use it in a topic question. State any assumptions and what evidence you would need before applying the idea to real work.
Sources
- IET: earthing and bonding FAQs — Protective bonding, earthing arrangements and loop impedance.
Where PEN conductor 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 most common modern UK supply arrangement: the distributor combines neutral and earth in a single conductor (the PEN) up to the service head, where it splits into separate neutral and earth for the installation. Its weakness is a broken PEN conductor, which can put the whole installation's earthed metalwork at a dangerous voltage — the reason special rules apply to EV charging and other outdoor equipment on PME supplies.
TN-C-S
Read the TN-C-S entryCompare related terms
Open a meaning to compare its role with PEN conductor, or follow its full entry.
TN-C-S — Protective Multiple Earthing (PME)
The most common modern UK supply arrangement: the distributor combines neutral and earth in a single conductor (the PEN) up to the service head, where it splits into separate neutral and earth for the installation. Its weakness is a broken PEN conductor, which can put the whole installation's earthed metalwork at a dangerous voltage — the reason special rules apply to EV charging and other outdoor equipment on PME supplies.
Read the TN-C-S entryOpen-PEN fault
A break in the PEN conductor of a TN-C-S (PME) supply, out in the distributor's cable. The building's loads then pull its neutral and earth terminal towards the line conductor's voltage, and everything bonded to them follows, while someone outdoors stands on real earth. An RCD won't catch it, which is why BS 7671 sets out specific options for outdoor EV charge points on PME.
Read the Open-PEN fault entryEarthing
Connecting an installation's exposed metalwork to earth, so that fault current has a deliberate path back to the supply. If the line conductor touches an earthed casing, that current lets a protective device switch the supply off automatically: a fuse or circuit breaker where the current is large, an RCD where it is small, as in a home with its own earth rod. Without earthing, a faulty casing can simply stay live.
Read the Earthing entryMain protective bonding
Conductors connecting extraneous-conductive-parts — incoming metal water, gas and oil services, and exposed structural steel — to the main earthing terminal. Bonding does not clear faults; while a fault lasts it keeps the touchable metalwork of a building much closer to the same potential, so a person touching a pipe and an appliance at the same moment bridges a far smaller voltage. It reduces the shock risk; the fault still has to be disconnected.
Read the Main protective bonding entryA definition is a start. Using it in a real question is where it sticks.