Why does the kettle or toaster trip the safety switch?

A kettle or toaster element is a resistance wire packed in insulating material inside a metal sheath or plate. Over time, scale, knocks and heat crack that insulation, or moisture gets into it. Some current then escapes to the metal body and the earth wire instead of returning the way it came. Energy Safe Victoria says a safety switch monitors the flow of electricity through a circuit and turns the power off within 0.03 of a second when it detects a problem that may put someone at risk.

Kettles also trip when water gets into the base or the connector after overfilling or a spill, and toasters when crumbs build up around the elements. These faults can be worse when the appliance is cold or damp and seem to clear once it warms up, which is why the trip can be hard to pin down.

Unplug the appliance and reset the safety switch once. Then plug it into a sound point in a different room, ideally one on a different safety switch, and switch it on. If that safety switch trips too, the appliance is the problem. If it works normally there, and the original point trips with other appliances as well, the point or the wiring on that circuit needs testing. Don't test anything in a point that is warm, marked or loose.

Look at which device dropped. A safety switch has a test button and 30mA printed on it, and it trips for leakage, often the instant the kettle switches on. A circuit breaker has no test button and trips for overload or a short.

A kettle, toaster and microwave running together on one kitchen circuit can draw more than the breaker allows, and it usually trips after a few seconds or minutes rather than instantly. That points to too much on one circuit rather than a faulty appliance. Spread the load, and if it happens every morning, a separate circuit for the bench may be worth adding.