A breaker that keeps tripping is annoying — but it's rarely a faulty breaker. The breaker is doing its job: protecting you from something dangerous. The trick is figuring out what that something is. Below are the seven most common causes I find when I'm called out for nuisance trips across Pinner, Hemel Hempstead, Harrow and the surrounding area.
1) The Circuit Is Genuinely Overloaded
Most likely cause, especially in older homes. A typical 32A ring main can run roughly 7kW of load before tripping. If you're running a kettle, microwave, washing machine and dishwasher all on the same kitchen ring, you'll trip it every time.
Quick test: unplug everything on the affected circuit, reset the breaker, then plug things back in one at a time. If it trips when you reach a specific appliance, that's your problem child. The fix is usually splitting the circuit (adding a new dedicated one for the heavy load) — typically 1-2 hours of work.
2) Earth Leakage (RCD Trips)
If it's an RCD that's tripping rather than a normal MCB, you've got electricity leaking to earth somewhere — even tiny amounts (30mA) will trip an RCD. Most common culprits: water ingress in an outdoor socket, a kettle or iron with damp internals, an immersion heater element going faulty.
These can be intermittent and infuriating to track down. I use an insulation resistance tester to find them in 30 minutes rather than guessing for hours. If you've got an RCD that trips during damp weather only, this is almost certainly it.
3) An Appliance With Failing Insulation
Older heating elements (kettles, ovens, immersion heaters, electric showers) eventually develop tiny insulation breakdowns. The appliance still works but trips the RCD when current leaks across the breakdown.
If unplugging one specific appliance solves the trips, you've found it. Replace the appliance — repair on most modern ones costs more than replacement.
4) Outdoor Circuit Moisture
Garden lights, hot tubs, EV chargers, outdoor sockets — anything outdoors is exposed to weather, and even IP-rated kit lets in moisture eventually. The classic symptom: trips during rain, fine when dry.
I see this a lot in older outdoor setups in Pinner where the original installer used standard indoor cable run outside. The right fix is replacing it with proper SWA cable rated for the environment.
5) A Damaged Cable Behind the Wall
Nail through a cable from a recent shelf install, mouse damage in the loft, screw into a cable behind a kitchen unit. Any of these creates an intermittent fault that trips when the wires touch.
These are tough to find without proper testing equipment — the location of the damage often isn't where you'd guess. An hour with a circuit tracer usually finds it. Then the fix is opening up the wall, cutting out the damage, and joining the cable in a maintenance-free junction box.
6) The Breaker Itself Has Failed
Rare, but happens. After thousands of trips an MCB or RCD can develop a faulty trip mechanism — false-positive trips that aren't responding to a real fault. £15 to swap the breaker, takes 10 minutes, but only worth doing once you've ruled out the other six causes above.
7) Your Consumer Unit Is Too Small for Modern Loads
Consumer units more than 15-20 years old were designed for a different era — no electric showers, no induction hobs, no EV chargers, no heat pumps. If you've added any of these and your board hasn't been upgraded, you're running outside the original design.
A modern 18th edition split-load consumer unit (£500 fitted in most homes) gives every circuit RCD protection, more breaker capacity, and properly distributed loads. If your house has had two or more major appliance upgrades since the board was fitted, this is almost certainly worth doing.
When to Call Me
Try the unplug-and-reset test from cause #1 first. If the trips happen with everything unplugged, or you can't isolate which appliance is doing it, give me a call — 07405 629 940. I cover Pinner, Hemel Hempstead, Harrow, Watford, Northwood, Eastcote and the surrounding area for fault-finding call-outs from £110 (often resolved in the first hour).