Residential · Troubleshooting
Why Your DB, RCCB or ELCB Keeps Tripping (and How to Find the Faulty Circuit)
A tripping breaker is annoying, but it is also your DB doing its job. In Malaysia the Fire and Rescue Department (JBPM) attributes about 60 per cent of house fires to electrical issues, and its Director-General named old wiring and switches that trip frequently as warning signs people tend to ignore (Bernama, 3 August 2025). This guide helps you understand which device tripped, find the cause safely, and decide when to call a registered electrician.
First, which device tripped?
Open your DB and look for the switch that is now down (OFF). Each device trips for a different reason:
| Device that tripped | What it protects against | Most likely causes |
|---|---|---|
| RCCB (the switch with a "T" test button) | Earth leakage: current escaping to earth, which can electrocute a person | Water heater element, damp outdoor light or socket, faulty appliance, wet wiring after rain, old insulation |
| MCB (small single switch for one circuit) | Overload or short circuit on that circuit | Too many appliances on one socket circuit, a shorted cable or appliance, loose connection |
| RCBO (MCB and RCD in one, often for the water heater) | Both, on one circuit | Water heater element leaking, wet heater, faulty heater wiring |
| Main switch | Very large overload | Rare in homes; usually a serious fault or undersized main switch |
"ELCB" or "RCCB"? Most Malaysians call the leakage device an ELCB. Modern boards use an RCCB, which measures current. The ST guideline (section 7.3) states that residual current devices must be current-operated and that voltage-operated ELCBs must not be used. If your DB still has an old voltage-type ELCB, it is due for an upgrade.
What does Malaysian law say about RCCB sensitivity?
Regulation 36 of the Electricity Regulations 1994 sets how sensitive the earth-leakage protection must be. ST's domestic wiring guideline tabulates it for homes (Table 7.2):
| Rated sensitivity | Required for | Legal basis |
|---|---|---|
| Not more than 10 mA | Wet locations: water heater, swimming pool, garden and fence lights | Reg 36(1)–(2) |
| Not more than 30 mA | 13A socket circuits, where hand-held appliances are used | Reg 36(3) |
| Not more than 100 mA | Other final circuits such as lighting, fans and aircond | Reg 36(4) |
The guideline also requires a water heater to be permanently connected through a 20 A or 32 A breaker with a residual current device of not more than 10 mA (section 9.1(h)(ii)). A 10 mA device is very sensitive, so a water heater with a slightly leaky element will trip it long before a 30 mA RCCB notices.
Sumber: Suruhanjaya Tenaga, GP/ST/No.39/2024; Electricity Regulations 1994.
How to find the faulty circuit in 5 minutes
Only do this if your DB cover is intact, your hands are dry and there is no burning smell. If you smell burning or see scorch marks, stop and call an electrician.
- Unplug appliances you suspect, especially anything used just before the trip (kettle, iron, washing machine, water heater).
- Switch every MCB off.
- Reset the RCCB (push it up). If it trips immediately with all MCBs off, the fault is in the DB itself or the incoming wiring. Call an electrician.
- Switch the MCBs on one at a time, waiting a few seconds between each.
- When the RCCB trips again, the last MCB you switched on is the faulty circuit. Leave that MCB off, reset the RCCB and switch the others back on.
- If it was a socket circuit, plug appliances back in one by one to see whether a single appliance is the cause.
Write down which circuit it was. It saves time and money when the electrician arrives.
The 8 most common causes in Malaysian homes
- Water heater element leaking. The single most common cause. Elements corrode over time; the 10 mA RCBO or RCCB trips when you switch the heater on or start showering.
- Rain and moisture. Outdoor lights, porch sockets, garden lights and the DB itself let water in during heavy rain. Trips that only happen when it rains point to this.
- A faulty appliance. Old refrigerators, washing machines, rice cookers and kettles with damaged insulation leak current to earth.
- Ageing insulation. Cable insulation in homes over 25 to 30 years old becomes brittle and leaks. See rewiring an old house.
- Neutral-to-earth faults. A neutral wire touching earth somewhere (often after renovation or a nail through a cable) trips the RCCB unpredictably.
- Overloaded socket circuit. Several high-power appliances (air fryer, microwave, kettle) on one circuit trip the MCB, not the RCCB.
- Lightning and voltage surges. Storms can trip RCCBs. A surge protective device (SPD) in the DB reduces damage to appliances.
- A worn-out RCCB. RCCBs can become oversensitive or fail. ST's testing rules require an RCD not to trip at 50% of its rated current and to trip within 200 ms at 100% (section 11.2.5). An electrician can test this with an RCD tester.
Is it safe to keep resetting it?
Resetting once to find the cause is fine. Repeatedly resetting a breaker that keeps tripping, or taping it up, is dangerous. JBPM's Director-General specifically warned that bypassing a damaged fuse or modifying electrical safety devices can lead to major fires, because the system then fails to cut the supply during a short circuit (RTM, 3 Ogos 2025). He also advised having home wiring inspected by a qualified electrician every 10 to 15 years.
How much does it cost to fix?
| Repair | Luco Group price |
|---|---|
| Replace an MCB | RM85 |
| Replace an RCCB | RM185 |
| Add an RCBO (e.g. for the water heater) | RM145 |
| Replace the whole DB (8-way / 12-way, single phase) | RM880 / RM1,180 |
A visit has a minimum charge of RM650, which covers diagnosis and the repair within that amount. If your board is old, compare the cost of a complete DB replacement or price one in our DB configurator.
When to call a registered electrician immediately
- The RCCB trips even with all MCBs off.
- You see scorch marks, melted plastic or smell burning at a socket or the DB.
- A socket or switch feels hot.
- You get a tingle or shock from an appliance, tap or metal surface.
- The same circuit trips again after you have unplugged everything.
Frequently asked questions
Why does my RCCB trip only when it rains? Water is getting into an outdoor light, socket, junction box or the DB. Switch off the outdoor circuit's MCB during rain and have the fitting resealed or replaced with an outdoor-rated (IP-rated) one.
Why does my water heater keep tripping? Usually the heating element is leaking current to earth, which the 10 mA protection detects. The heater element or the heater itself needs replacing; the RCBO is doing its job.
What is the difference between an RCCB and an ELCB? "ELCB" is the old name. Modern RCCBs detect leakage by measuring current; old voltage-operated ELCBs are no longer allowed under the ST guideline.
Can I just replace the RCCB with a less sensitive one? No. The sensitivity is set by Regulation 36 of the Electricity Regulations 1994: 10 mA for wet areas, 30 mA for sockets and 100 mA for other circuits.
Why does the RCCB trip at night with nothing switched on? Something is always on: the fridge, aircond standby, outdoor lights on a timer, or moisture building up as temperatures drop. The isolation steps above will find the circuit.
Sources
- Suruhanjaya Tenaga, Garis Panduan Pendawaian Elektrik Pepasangan Domestik (GP/ST/No.39/2024): Table 7.2, sections 7.3, 9.1(h), 11.2.5. st.gov.my PDF
- Electricity Regulations 1994, Regulation 36. st.gov.my PDF
- Bernama, JBPM attributes 60 pct of house fires to electrical issues, 3 August 2025. bernama.com
- RTM Berita, Peralatan elektrik, punca 60% kes kebakaran rumah, 3 Ogos 2025. berita.rtm.gov.my
This guide is general information, not a substitute for an inspection by a registered electrical contractor. Regulations and TNB charges change; always check the linked official sources.