Short answer: the most common reason a fuse board (consumer unit) keeps tripping is a faulty appliance leaking current to earth, which the RCD detects. Unplug everything, reset the board, then plug items back in one at a time — when it trips again, you’ve found the culprit. If it trips instantly with nothing plugged in, you have a fixed wiring fault and need an electrician.
Repeated tripping is your electrical system doing its job — cutting power before a fault becomes a fire or a shock. Here are the 12 causes we diagnose most across London, in order of likelihood, and what to do about each.
First — which switch is tripping?
- One small switch (MCB): a single circuit is overloaded or has a fault — note which circuit and what was running.
- The wider RCD switch (covers several circuits): something is leaking current to earth — usually an appliance or damp.
- The main switch / everything at once: rare — could be a supply-side issue or a failing board. Call an electrician.
The 12 most common causes
1. Faulty appliance (the cause in most cases)
Kettles, washing machines, tumble dryers, immersion heaters and old fridge-freezers top the list. Insulation inside degrades and leaks current. Find it by elimination: unplug all, reset, reconnect one at a time.
2. Overloaded circuit
Kettle + toaster + microwave + air fryer on one kitchen ring can exceed its rating. If the MCB trips when several heavy loads run together, spread them across circuits — or the circuit needs upgrading.
3. Water ingress — bathroom, kitchen or outdoor circuits
Damp in an outside socket, garden lighting, or around a shower is a classic RCD trip, especially after rain. Outdoor circuits that trip in wet weather need re-sealing or re-routing.
4. Damaged cable
A nail or screw through a cable, a pinched cable behind furniture, or rodent damage. Trips are often instant on reset. This is a job for an electrician with test equipment.
5. Lighting circuit fault
A failed lamp can trip an MCB at the moment of failure; recurring lighting trips point to a deteriorated fitting or connection.
6. Old electric shower failing
Showers draw the biggest load in most homes. A failing element leaks to earth and trips the RCD mid-shower — a very recognisable pattern.
7. Loose connection in the board
Loose terminals arc, overheat and trip. Warm switches, buzzing or scorch marks at the board mean switch off and call us — this is how consumer-unit fires start.
8. Nuisance tripping from accumulated earth leakage
Many modern electronics each leak a tiny, legal amount. Add enough devices on one RCD and it sits near its threshold, tripping at random. The fix is usually splitting circuits across RCBOs during a fuse board replacement.
9. Failing RCD or MCB itself
Protective devices age. If testing shows the RCD trips well below its rated current, the device — not your wiring — is the fault.
10. EV charger on an unsuitable supply
A 7kW charger added to an older board can cause repeated trips or worse. Chargers need correct RCD types (usually Type A with DC detection) and load management.
11. Surge or storm damage
After a lightning storm or grid switching surge, sensitive devices and even MCBs can be left damaged and trip-happy.
12. Damaged extension leads and outdoor kit
Trailing leads, hedge-trimmer cables and cheap outdoor sockets are frequent culprits — and the easiest fix of all: bin them.
When to stop resetting and call an electrician
Stop resetting and call us if: the board trips instantly every time with nothing plugged in; you smell burning or see scorch marks (see burning smell from a socket); a socket circuit is dead and won’t come back (socket not working?); or the trips are getting more frequent. Repeatedly forcing a tripping board onto a live fault is dangerous.
For out-of-hours faults we run a 24-hour emergency electrician service across North and East London.
Is the fuse board itself the problem?
If your board is an old rewirable-fuse or plastic unit with no RCD protection, recurring trips are often the symptom of a board past its service life. See our guides to consumer unit upgrades and fuse board replacement costs — replacements from £550 labour-only, with modern RCBOs that stop one faulty circuit taking out the whole house. Wondering about doing it yourself? Read do I need an electrician to change a consumer unit?
Frequently asked questions
Why does my fuse board trip at the same time every day?
A pattern points to a scheduled load — immersion heater timer, storage heater, dishwasher cycle. Whatever switches on at that time is your suspect.
Is a tripping fuse board dangerous?
The tripping itself is the safety system working. The danger is the underlying fault — and repeatedly resetting onto a live fault can overheat cables. Find the cause; don’t just keep resetting.
How much does it cost to find a tripping fault in London?
Our minimum charge is £108 (£90 + VAT) labour-only, and most trip faults are diagnosed within the first hour using insulation-resistance testing. You’ll get a clear quote before any remedial work.
Get it diagnosed properly
F & A Electrical is a NICEIC-approved contractor in Tottenham N15, rated 9.32/10 from 242 reviews, covering North and East London usually within 48 hours. Call 07407 627 542 — or read our local guide, fuse box keeps tripping in London, for what to check before we arrive.