Domestic
Fuse box keeps tripping? Seven common causes and when to call an electrician
14 August 2026 · 6 min read
From a failing kettle to water in an outside light, here are the seven things that most often trip an RCD, and how to narrow it down yourself.
A tripping fuse box is not a fault in itself. It is your protection working. The question is what is triggering it, and whether the answer is a £30 appliance or a circuit that needs attention.
1. A faulty appliance
By far the most common cause. Kettles, washing machines, dishwashers, immersion heaters and older fridges develop insulation faults as their heating elements age. Unplug everything on the affected circuit, reset, then plug items back in one at a time until it trips.
2. Water ingress
Rain in an outside socket, a leaking shower tray, a roof leak above a ceiling rose or a flooded external light. Water tracking across terminals causes exactly the small earth leakage an RCD is designed to catch. Faults that appear only after rain are almost always this.
3. Cumulative earth leakage
Every appliance leaks a tiny current to earth. Individually harmless, collectively enough to nudge a 30 mA RCD over its threshold, especially where one RCD protects half the house. The fix is usually splitting circuits across individual RCBOs rather than replacing appliances.
4. Overloaded circuits
A breaker that trips when several high demand appliances run together is telling you the circuit is at capacity. Kitchens in older houses are the usual culprit. Adding a dedicated circuit is the correct answer, not fitting a larger breaker.
5. Damaged cabling
A screw or a nail through a cable during shelving, flooring or loft work, or rodent damage in a roof space. These faults are often intermittent and need proper testing to locate.
6. Failing light fittings and dimmers
Cheap LED lamps and incompatible dimmers cause switch on surges that trip breakers, particularly on circuits with a lot of downlights. The tell is that it trips at the moment a light is switched on and never otherwise.
7. A faulty RCD or breaker
Protective devices wear out. Where testing shows no fault on the circuit, the device itself may be dropping out below its rated threshold and should be replaced.
When to stop and call
- It trips with everything unplugged
- There is a burning smell, buzzing or scorching
- It trips repeatedly with no obvious pattern
- The board has rewireable fuses or no RCD protection at all
- Resetting has become part of your weekly routine
We find the actual fault with test instruments rather than swapping parts and hoping. Call 01634 944 145 and we will get to the bottom of it.
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