What is this?
A dedicated lighting circuit MCB (typically rated at 6A) keeps tripping, turning off all the lights on that circuit. UK homes usually have one or two lighting circuits, so the trip may affect lights throughout the house or on one floor. Lighting circuit faults are often related to light fittings, switches, or wiring in the loft and ceiling voids.
Common causes
- Faulty light fitting with a short circuit or earth fault
- Incorrect bulb type or wattage causing overheating in a fitting
- Loose connection at a ceiling rose, junction box, or light switch
- LED downlight driver failure causing a short circuit
- Water ingress into a ceiling light from a leak above
- Damaged cable in the loft, especially if disturbed during loft boarding or insulation work
Is it dangerous?
A tripping lighting circuit is not an immediate danger, but it does leave you in the dark, which creates trip and fall hazards, especially on stairs. The underlying fault — particularly loose connections in ceiling roses — can cause arcing and overheating, which is a fire risk. Do not ignore persistent tripping.
Can I fix it myself?
Switch off all the light switches in the house (or on the affected floor) and reset the MCB. Turn lights on one at a time. If a particular light causes the trip, the fitting or its connections are faulty. Check if you recently changed any bulbs — incompatible LED bulbs or wrong-wattage bulbs can cause problems. Do not remove or open light fittings unless you have isolated the circuit.
When to call an electrician
Call an electrician if you cannot identify which light is causing the trip, if the circuit trips with all lights off (suggesting a wiring fault), if you have recessed downlights that may have overheated, or if there are any signs of water near a light fitting. Lighting circuit work should be carried out by a qualified electrician.
What will an electrician do?
Test the lighting circuit for short circuits and earth faults
Inspect each light fitting, ceiling rose, and junction box for loose connections
Check LED drivers and transformers for faults
Inspect loft wiring for physical damage or disturbed connections
Replace faulty fittings, drivers, or connections
Test the circuit after repair and verify all lights operate correctly
Typical cost
£80 – £200
Most lighting faults are in fittings or connections and are relatively quick to fix. Costs increase if loft access is difficult or cables need replacing.
