Lighting Circuit Basics

A lighting circuit in a UK home is typically a 6A radial running from the consumer unit to each light fitting and its switch. Unlike socket circuits, lighting circuits do not form a ring.

Basic Structure

Cable

Lighting circuits use 1mm² 2-core + earth T&E. This is appropriate because:

• The 6A MCB limits current to 6A
• Light fittings draw very little current (even a 100W lamp is less than 0.5A)

Switch Wiring

Each light fitting has a switch drop — a cable that runs from the ceiling rose (or junction box) down to the wall switch. Only the live conductors go to the switch; the neutral stays at the rose.

Two Wiring Methods

UK lighting circuits use one of two methods:

• Loop-in (3-plate) — supply looped through each ceiling rose
• Junction box method — supply runs to a junction box; separate cables go to rose and switch

Both are valid under BS 7671. Loop-in is more common in modern installations.