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Lesson: Chapter 10 — Power and energy in electrical appliances

Wiring and safety 2 of 3

The protective devices

A household circuit has two basic protective devices: the RCCB, and the MCBs or fuses.

RCCB (trip switch)

Cuts the supply when someone gets a shock or an appliance leaks current.

Switches off the whole house.

Also trips if more than 30 A flows into the house, preventing fires from hot main cables.

MCB or fuse

Stops an overload in its own circuit, and the fire it could start.

Gives no protection from a leak or a shock.

When the supply goes off

  1. Switch the overload circuit breaker OFF.
  2. Put the RCCB or the tripped MCB's lever up (ON).
  3. Switch the overload circuit breaker ON again.
  4. If it cuts out again, have an electrician find the fault.