What causes a split neutral fault and why is it dangerous?

What Is a Split Neutral Fault? A split neutral fault happens when the neutral wire in your electrical circuit breaks or becomes disconnected, while the live wire stays connected and energised. In a healthy circuit, current flows out through the live wire and returns safely through the neutral. When the neutral is broken, that return path is lost — and electricity can behave in very unexpected and dangerous ways. Why Is It So Dangerous? Unlike a blown fuse or tripped breaker, a split neutral doesn't always cut the power. Instead, it can: Make metal casing on appliances become live at mains voltage (230V) Cause lights to flicker, dim, or burn extremely bright as voltage shifts unpredictably Allow current to return through earth conductors or pipework, creating hidden shock and fire risks Fool you into thinking a circuit is safe when it isn't Common Causes Loose or corroded neutral terminal at the consumer unit, junction box, or socket Rodent damage to cable insulation and conductors in roof spaces or underfloor areas Old wiring with aluminium neutrals that have corroded at terminations Poor workmanship — an undertightened screw terminal that has gradually worked loose Mechanical damage to cables during building works or DIY What You Might Notice Lights flickering or changing brightness for no obvious reason Appliances behaving erratically or failing A mild tingling sensation when touching metal appliances Burning smell near sockets, light fittings, or the consumer unit RCD tripping repeatedly without a clear reason What You Should Do Do not investigate live wiring yourself. A split neutral is one of the most deceptive faults in domestic electrics because circuits may appear dead but still carry dangerous voltages. 1. Switch off the affected circuit at the consumer unit 2. Unplug all appliances on that circuit 3. Call a Part P registered electrician immediately — use the NICEIC or ELECSA online registers to find one 4. If you have any doubt about safety, switch off the main switch at the consumer unit This is a C1 (Danger Present) category fault under EICR classifications — it requires immediate rectification.