A circuit breaker that trips is interrupting a circuit for a reason. The useful clues are what lost power, what was running and whether there were signs of heat, damage or moisture. The switch position alone cannot tell you what has failed.
For smoke, fire or immediate danger, leave and call 000. Do not touch damaged equipment or approach a wet, hot or damaged switchboard. A shock or tingle needs urgent attention: keep away and contact emergency services and your electricity distributor.
Breaker, safety switch or both?
Circuit breaker (MCB). Responds to excess current from an overload or short circuit. A trip alone does not identify the appliance or part of the wiring that caused it.
Safety switch (RCD). Responds to a current imbalance that can indicate leakage to earth. A trip does not establish that an overloaded circuit is the cause.
Combined device (RCBO). Provides both overcurrent and earth-leakage protection. Further investigation is needed to establish which protection operated and why.
An RCD or RCBO usually has a test button. Read accessible labels only; do not remove a switchboard cover to identify equipment. Our RCD tripping guide explains that particular problem.
Why a circuit breaker may trip
Too much load on one circuit
Several appliances can share a circuit even when they use different outlets. Running high-load equipment together may exceed its capacity. Adding a power board or another powerpoint does not increase the available capacity.
A short circuit or damaged equipment
An appliance, cable or fixed-wiring fault can cause excess current. A trip as something starts is useful information, but is not proof that the appliance is the only fault.
The protective device or its connections
A breaker or connection can need attention too. Testing is needed before deciding whether replacement is appropriate. Installing a higher-rated breaker without checking the wiring and installation is not a safe solution.
If an RCBO has operated, earth leakage is another possibility. Correctly identifying the device matters.
What you can safely note
From a safe position, note:
- Whether one circuit, several circuits or the whole property lost power.
- What was running when it happened.
- Whether it followed rain, cleaning, a spill or building work.
- Any smell, unusual noise, visible damage or previous trips.
- What the accessible circuit label says.
Do not recreate the fault or touch equipment to see whether it is hot. You do not need to open covers, disconnect wiring or carry out tests before calling.
Should you reset it?
Do not reset a device when there is damage, water, heat, a burning smell, a shock or another sign of danger. Do not approach an unsafe switchboard.
Where there are no warning signs, the board is dry and undamaged, and you can safely follow the device manufacturer's user instructions, a single reset may be appropriate. If it trips again or will not stay on, leave it off and arrange an electrician. Do not keep resetting it to maintain power.
A suspect appliance should stay out of use. Unplug it only if the plug and outlet are safe to touch; otherwise keep clear.
What an electrician checks
The investigation can include the circuit load, wiring condition, connections, connected equipment and operation of the protective device. The repair depends on the findings: it might involve an appliance, a damaged connection, circuit work or a protective-device replacement.
A whole switchboard upgrade is not the automatic answer to one tripping circuit. AB Electrical can explain the fault found and whether a targeted repair or broader work is needed.
When it is urgent and when it can wait
A breaker that trips once with a clear cause, such as a heater and a kettle running together, then resets and stays on is a capacity question to raise at a planned visit. A breaker that trips again, will not reset, or trips with nothing obvious running needs investigation; leave it off in the meantime.
Treat it as urgent when the trip follows a bang, a burning smell, heat or discolouration at the board or an outlet, water reaching equipment, a shock or tingle, or when it removes power from medical equipment, refrigeration or a business that cannot operate. Those calls are taken at any hour.
Common misunderstandings
A bigger breaker will stop the tripping. The breaker is sized to protect the cable behind it. Fitting a larger device leaves the cable unprotected and does not change how much the circuit can safely carry.
A tripped breaker means the appliance is broken. The appliance that was starting is a clue, not a diagnosis. The fault may be in the appliance, the lead, the outlet, the circuit wiring or the device itself.
A whole new switchboard is needed. One tripping circuit is usually a circuit or equipment fault. The board may need attention for other reasons, but the trip alone does not establish that.
Nothing changed, so it cannot be an overload. Equipment is used differently across the seasons, appliances are added over time, and a circuit that has been close to its limit for years can tip over with one small change.
When to call
Call about a repeated trip or a circuit that will not stay on. Explain any hazards and whether essential equipment is affected so attendance can be discussed. For an urgent electrical fault, call from a safe place rather than waiting for a form response.
If you are adding equipment to an otherwise working installation, a planned circuit or powerpoint assessment can establish what it will support.
For immediate electrical hazards, see Ausgrid's emergency guidance (opens in new tab).
For a trip with a burning smell, heat, water or a shock involved, call 0405 343 343 from a safe place. For a circuit that can safely stay off until a planned visit, or for a capacity assessment, send an enquiry with your suburb, a short description of what trips and what was running, and photos of the closed board only if they can be taken safely.
