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Key points

  • Many appliances leak a small, normal current to earth, and their total on one RCD can cause 'unexplained' tripping.
  • BS 7671 guidance: accumulated protective conductor currents downstream of an RCD should not exceed 30% of its rated residual current (under 10 mA for a 30 mA RCD).
  • An RCD may operate at any residual current above 50% of its rating, so subdividing circuits across more than one RCD is the real fix.
  • Surge protective devices (SPDs) protect against transient overvoltages from lightning and switching: Type 1 at the service entrance, Type 2 at the main board, Type 3 near sensitive equipment.
Written for:OwnerContractor
First of all: don't open the consumer unit or take apart live sockets. This guide is for understanding the problem and describing it accurately to the electrician. See when to call a professional.

1) The RCD trips for no obvious reason

A residual current device (RCD) cuts the power when current leaks to earth, and it protects lives. See breakers and RCDs. But repeated tripping is not always "a faulty RCD". The UK Institution of Engineering and Technology (IET) explains1:

  • Unwanted tripping is likely where an RCD protects circuits with high normal protective conductor (leakage) currents, especially socket circuits where it isn't known what will be plugged in.
  • Under regulation 531.3.2 of BS 7671: the accumulation of these currents downstream of the RCD should not exceed 30% of its rated residual operating current — less than 10 mA for a 30 mA RCD.
  • Under product standards, an RCD may operate at any residual current above 50% of its rating — about 15 mA for a 30 mA device.
  • The fundamental fix: divide the installation into several final circuits so leakage doesn't accumulate on one device.

A simple check you can do safely

A common practical method to isolate the cause, without opening any board or socket.

  1. Unplug all appliances.
  2. Reset the RCD.
  3. Plug the appliances back in one at a time, waiting a little after each.
  4. If it trips on one particular appliance every time, the fault is probably in it (especially appliances with heaters and motors: washing machine, oven, water heater).
  5. If it trips with everything unplugged: the problem is in the wiring (moisture in a box, damaged cable); call an electrician.
Never remove the RCD or replace it with an ordinary breaker to stop the tripping. That removes your protection against electric shock.

2) A hot socket or burning smell

Practical danger signs; switch off that circuit's breaker immediately and call an electrician.

  • Common causes: a loose connection in the socket, a poor-quality socket, or overload (a heater or AC on an ordinary socket or multi-way adaptor).
  • Signs: brown discolouration or melting on the socket, a hot plug, crackling.
  • Large loads (ACs, water heaters, ovens) must be on dedicated circuits. See wires and circuits and voltage and plugs in Saudi Arabia.

3) An ordinary breaker trips

  • Trips when a large appliance starts: overload on the circuit; spread the loads or ask for a dedicated circuit.
  • Trips immediately when reset: possible short circuit; don't keep resetting, call an electrician.

4) Protecting appliances from transient overvoltage (SPD)

Surge protective devices divert high surge currents safely to earth and limit transient overvoltages that could damage equipment, whether from lightning or from switching in the network2.

TypeUse and location
Type 1For direct lightning strikes; installed as close as possible to the origin or point of entry of the electrical service2.
Type 2For indirect risks; installed as close as possible to the origin of the installation (main board)2.
Type 3For protecting sensitive equipment; in sub-boards, near equipment, or in socket-outlets2.

Choosing the type, coordinating types and earthing them is a job for a qualified electrician. Cheap "surge-protected" extension leads are no substitute for protection at the board.

5) Flickering lights

  • One lamp: a poor lamp or driver, or incompatibility with a dimmer.
  • The whole house, or when the AC starts: possibly a weak connection or supply problem; ask for an electrician's inspection.

Sources

The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.

  1. 1High Protective Conductor Currents in Electrical Installations (Regulation 531.3.2) — The Institution of Engineering and Technology (IET) — Wiring Matters
  2. 2Types of SPD and their use in electrical installations — NICEIC
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This guide is for general information and planning, based on standards and technical guides. Standards are revised periodically; in Saudi Arabia the binding reference is the Saudi Building Code and the instructions of the competent authorities. For design and execution, use a licensed engineer or technician. Found an error? Tell us.