A circuit breaker or RCD that trips once is usually nothing to worry about. One that trips repeatedly — especially on the same circuit, or for no apparent reason — is telling you something. Ignoring it risks more than inconvenience: an underlying fault left untreated can overheat cables or, in serious cases, cause a fire.
Understanding What's in Your Consumer Unit
Modern consumer units contain two types of protective device. MCBs (Miniature Circuit Breakers) protect individual circuits from overload and short circuit. RCDs (Residual Current Devices) — the wider switches — protect groups of circuits against earth faults and reduce the risk of electrocution. Some boards use RCBOs, which combine both functions on a single circuit. Knowing which device is tripping tells you a great deal about the likely fault.
"An RCD tripping when nothing is obviously wrong may indicate current leaking to earth somewhere in the circuit — possibly from a faulty appliance, damp wiring, or a deteriorating cable. It should not be ignored."— NICEIC — RCD Protection Guidance
The Most Common Causes
Overloaded circuit
Each circuit has a rated maximum load. Plugging too many appliances into one ring or spur — common in kitchens — causes the MCB to trip on overload. The fix: spread the load, or have an additional circuit installed.
Faulty appliance
A damaged cable, failing element, or water ingress in an appliance can cause an earth fault that trips the RCD. Test by unplugging everything on the affected circuit, resetting the RCD, and re-plugging appliances one at a time. If the RCD holds until a specific appliance is plugged in, that appliance is the culprit.
Wiring fault
Damaged insulation, rodent damage, a nail through a cable, or a poorly made joint can create a persistent fault. These rarely self-resolve and require a fault-finding visit from a registered electrician.
Nuisance tripping from LED downlights
Some RCDs trip intermittently with LED transformers, particularly cheap or incompatible units. This is a known issue. An electrician can advise on compatible LED drivers or fit RCBOs to separate circuits.
What You Can Safely Do Yourself
Resetting a tripped MCB or RCD is safe. Unplugging appliances to identify a faulty device is safe. Beyond that — opening accessories, poking at wiring, or attempting to bypass a tripping device — is not. If the RCD continues to trip with everything unplugged, or if it trips immediately on reset, there is a wiring fault that requires professional diagnosis.
When to Call an Electrician Immediately
Call without delay if: the board feels warm or smells of burning; the RCD trips and won't stay reset even with everything unplugged; you see scorch marks or discolouration on sockets or the board itself; or the tripping is accompanied by flickering lights across the house (which may indicate a loose neutral connection — a potentially dangerous fault).
"A loose neutral connection can cause voltage imbalance and overheating across the installation. It is one of the less obvious but more serious faults we see — homeowners sometimes tolerate flickering lights for months before calling us."— NAPIT — Electrical Safety for Homeowners
Fault-Finding: What the Electrician Will Do
A competent fault-finding visit involves: visual inspection of the consumer unit and any accessible wiring; insulation resistance testing on the affected circuit(s); loop impedance testing to check earth continuity; and RCD trip-time testing. The electrician will give you a written report and, if a fault is confirmed in fixed wiring, a Minor Electrical Installation Works Certificate on completion of the repair.
Need a Registered Electrician?
Firquote connects you with NICEIC- and NAPIT-registered electricians in your area — free quotes, no obligation.
Get Free Quotes →