Why does my power keep tripping? RCCB and MCB trips explained

Know your DB box

Your distribution board (DB box) usually has:

• A main switch (isolator) for the whole house.
• An RCCB — residual current circuit breaker. Many Malaysians still call it the ELCB. It watches for current leaking to earth, the kind that can give someone a shock, and cuts the power within a fraction of a second.
• A row of MCBs — miniature circuit breakers — one per circuit (lights, sockets, water heater, aircond, kitchen…). Each trips if its circuit draws too much current or short-circuits.

Which one has tripped tells you a lot about the cause.

If the RCCB/ELCB trips: earth leakage

Common causes in KL homes:

• Water getting in — outdoor sockets, porch or garden lights, the aircond outdoor unit or a cracked socket near the sink, especially after heavy rain.
• Water heaters — a failing heating element in an instant or storage heater is one of the most frequent culprits.
• Old or damaged appliances — kettles, rice cookers, washing machines and irons with worn insulation.
• Damp wiring — water seeping into a wall or ceiling from a leak above and reaching a junction box or light fitting.

If an MCB trips: overload or short circuit

• Overload — too many high-power appliances on one circuit (iron + kettle + microwave on the kitchen sockets, or extension cords running everything from one point).
• Short circuit — a damaged cable, a loose connection or a failed appliance. This often trips instantly and may leave a burn mark or smell.

How to find the culprit safely

1. Switch off or unplug everything you can: appliances, the water heater switch, aircond isolators.
2. Switch all MCBs off, then switch the RCCB on.
3. Switch MCBs on one at a time. If the RCCB trips when a particular MCB goes on, the fault is on that circuit.
4. On that circuit, plug appliances back in one by one until it trips again — that appliance is your suspect.
5. If it trips with nothing plugged in, the fault is in the fixed wiring, a socket, a light or the water heater — that needs an electrician.

What not to do

• Don’t hold the switch up or tape it to stop it tripping.
• Don’t replace the RCCB with a less sensitive one to “fix” nuisance trips — it is there to prevent electric shock.
• Don’t open the DB box cover or touch wiring yourself.

When to call an electrician

• The RCCB trips again with all appliances unplugged.
• It trips every time it rains.
• Sockets or switches are warm, cracked or discoloured.
• The house is 25–30+ years old and still has its original DB box and wiring.

An electrician tests each circuit with an insulation tester, finds the faulty point and repairs it. New circuits, DB box replacements and rewiring in Malaysia must be carried out and tested by a registered electrical contractor and competent wireman under Energy Commission (Suruhanjaya Tenaga) rules. See our electrical service.

Typical costs in Kuala Lumpur