Protection

Distribution Board

Where the supply splits into final circuits, each with its own protection and its own switch.

Photorealistic consumer unit with the cover removed
Real part — tap a marker

Distribution Board

Where the supply splits into final circuits, each with its own protection and its own switch.

Terminals
  • L-in and N-in from the meter and main earthing terminal
  • Circuit protective conductors to the earth bar
  • Neutral bar and earth bar — one way per circuit
  • Main earthing terminal and bonding connections
  • Enclosure — metal on modern boards, with a hinged cover
  • Main switch — a double-pole isolator for the whole board
  • Circuit breakers, RCBOs and RCDs on a DIN rail
  • Busbar — the copper strip feeding the protective devices
  • Neutral bar and earth bar
  • DIN rail and blanking modules
  • Circuit schedule and labels
Cutaway of a distribution board showing the DIN rail, busbar, main switch, protective devices, neutral bar and earth bar
Cutaway — tap a marker
⚡ Meet it in a circuit

Terms used here

Defined in the glossary — each one opens at its own entry.

⚠ Safety note

Live parts inside a consumer unit stay live with every circuit breaker off — only the main switch (or the cut-out fuse before it) makes the board safe. Only a competent person should remove a cover, and the supply must be isolated and proved dead first. Also note that a metal board and its circuits must be earthed and the bonding verified.

More components
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