RCD Keeps Tripping: Causes and What to Report

What's happening?

An RCD detects an imbalance between the current flowing out and returning, and disconnects the supply when its operating conditions are met. Repeated tripping can involve an appliance, damaged wiring, moisture, accumulated leakage or the protective device itself. The symptom needs investigation; tripping does not prove that every aspect of the protection is working correctly.

What usually causes it?

• Faulty appliance with a breakdown in its internal insulation: the most common cause of RCD tripping in UK homes. Washing machines, tumble dryers, dishwashers, and kettles are frequent culprits as their heating elements degrade over time
• Damaged cable or wiring with degraded insulation, allowing current to leak to earth. This is especially common in older properties with rubber or lead-sheathed wiring that has become brittle with age
• Moisture or condensation in a socket, junction box, light fitting, or outdoor enclosure. Even small amounts of dampness can create an earth leakage path that exceeds the 30mA threshold
• A protective device that needs inspection and testing; replacement depends on its condition and test results
• Accumulated leakage from several connected appliances on the protected circuits
• Outdoor wiring or garden equipment exposed to damp conditions: garden lights, pond pumps, hot tub circuits, and external sockets are particularly vulnerable
• A fault or unsuitable protection involving connected equipment, requiring assessment against the installation and equipment requirements
• Rodent damage to cable insulation inside walls, lofts, or under floors
• Incorrectly wired circuits, particularly where a neutral from one circuit has been connected to another circuit (a crossed neutral)
• Immersion heater or electric shower with a failing heating element that allows current to leak through the water to earth

Is it dangerous?

The underlying fault can be dangerous. Never bypass, disable or hold an RCD on. Keep clear of wet, damaged or overheating equipment and stop repeated resets. If there is smoke or fire, leave and call 999. A competent electrician should investigate repeated tripping.

Can I fix it myself?

Record what was happening when the trip occurred and leave suspect equipment out of use. Do not test by reconnecting appliances one at a time, open the consumer unit or touch wet fittings. If the supply cannot be restored safely using the installation’s instructions, or it trips again, arrange an electrician to investigate.

When should you call an electrician?

Arrange a competent electrician when tripping repeats, the cause is unknown, or the device will not remain on. Describe any wet fitting, burning smell, recent work or appliance in use. Do not repeatedly reset to locate the fault or assume that an empty socket means fixed wiring is the only possible cause.

What will the electrician actually do?

• Perform RCD function tests using a calibrated RCD tester to confirm the device itself is operating within specification: tripping at the correct current and within the required time
• Carry out insulation resistance (IR) testing on each circuit to measure the level of earth leakage and identify which circuit or circuits have degraded insulation
• Perform a loop impedance test to verify the earth fault path is adequate and to rule out issues with the earthing system
• Use a process of elimination to systematically isolate the faulty circuit, then narrow down to the specific cable run, fitting, or accessory
• Inspect wiring, connections, junction boxes, and fittings on the faulty circuit for signs of damage, moisture ingress, overheating, or rodent damage
• Repair or replace the source of the fault: whether that is a section of cable, a damaged socket or light fitting, a faulty appliance connection, or a waterlogged outdoor enclosure
• Test the RCD again after the repair to confirm the fault is fully resolved and the device is holding
• Explain any proposed change to circuit protection from the cause, installation and test results rather than treat a new board as the default repair

Useful observations for a fault finding visit

Write down when power went off, which rooms lost power, which appliance was in use, any rain or leak and recent work. A photo of the closed consumer unit and its labels may help if it is safely accessible. Do not remove covers or repeatedly recreate the trip.

Ask for a fault finding stage with an agreed charge or time limit, a report of the findings and a separate decision on repairs. Explain access and any essential equipment affected. A tripping device alone does not establish that the consumer unit needs replacement.

Understand the fault finding visit and cost scope

Request a quote for the tripping fault

Who fixes this

• Electrical fault finding

What it usually costs

Electrical Fault Finding Cost

Priced on survey

Questions people ask

Sources & References

1. HSE: electrical faults, RCDs and competence
2. BS 7671: IET Wiring Regulations (18th Edition, Amendment 2)
3. IET: BS 7671 Guidance Publications
4. Electrical Safety First: Homebuyer Electrical Safety
5. NICEIC: Householder Guidance
6. HSE: Electrical Safety at Work