Stop if there is heat, burning, arcing, exposed parts or water near electrics
Do not remove consumer-unit covers, open sockets or test exposed conductors. Leave affected circuits off and call a registered electrician where danger signs or fixed wiring faults are present.
MOST LIKELY CAUSES
Start with these
Symptom variations Match the exact behaviour before testing. ⌄
- Trips immediately when reset
- Trips only when several appliances run together
- Trips when one appliance starts
- Trips after the circuit has been loaded for some time
- Trips with heat, burning smell or buzzing
Quick checks Safe checks using plugs and front-panel switches only. ⌄
- Identify which device has operated.
- Note what was running when the fault happened.
- Unplug portable appliances on the affected circuit or RCD group.
- Check recent rain, leaks, cleaning, building work or newly connected equipment.
- Attempt one controlled reset only.
Fix 1 — Reduce the load Follow this check without opening electrical accessories. ⌄
Process
Switch off and unplug high-power appliances on the circuit, then reset once.
Fix 2 — Identify a faulty appliance Follow this check without opening electrical accessories. ⌄
Process
Reconnect appliances one at a time until the breaker trips.
Fix 3 — Leave the circuit off if it trips immediately Follow this check without opening electrical accessories. ⌄
Process
Do not repeatedly reset an instant-trip breaker.
Common causes explained Why the fault may happen. ⌄
A circuit breaker that repeatedly trips usually indicates overload, short circuit, damaged wiring, a faulty appliance or a failed fixed load.
Protective devices are usually reacting to a real electrical condition rather than causing it. Repeated resetting without finding the cause is not a repair.
Advanced diagnostics Technician-level testing for a competent electrician. ⌄
- Verify breaker rating, type and cable compatibility.
- Measure load current under normal operation.
- Carry out insulation-resistance and continuity testing.
- Inspect accessories and junctions for heat damage.
- Test permanently connected loads and motors.
Tools needed Basic checks versus professional testing. ⌄
For basic checks
- Torch
- Phone or notepad
- Known-good low-power appliance where appropriate
For a competent electrician
- Approved voltage indicator and proving unit
- Multifunction installation tester
- Insulation-resistance tester
- Leakage clamp meter
- Suitable insulated tools and PPE
Parts that may need replacing Common failed components linked to this fault. ⌄
- Faulty appliance
- Damaged socket or switch
- Cable section
- Junction or connection
- Circuit breaker after confirmed failure
When to call an electrician Conditions that should end DIY troubleshooting. ⌄
- The fault remains with portable appliances unplugged.
- There is burning, heat, buzzing, crackling or visible damage.
- Water may have reached fixed electrical equipment.
- The consumer unit is damaged, poorly labelled or has exposed parts.
- The issue affects a shower, cooker, immersion heater, boiler or outdoor circuit.
- The protective device will not reset or operates repeatedly.
Frequently asked questions Common questions about this fault. ⌄
Should I keep resetting it?
No. One controlled reset can help establish whether the fault remains. Repeated resets without diagnosis are unsafe.
Does the protective device itself need replacing?
Not necessarily. The circuit and connected equipment should be tested before the device is replaced.
Can one appliance affect several rooms?
Yes. One protective device may control several circuits or areas.