MCB keeps tripping when I turn on the water heater
Every time the water heater (geyser) kicks in, the breaker trips and cuts power to that circuit. If I reset it and don't use hot water, it's fine. Is this something I can reset and ignore, or a real problem?
3 answers
Do not just keep resetting it — that trip is doing its job.
A breaker that trips specifically when the heater energises almost always means the heating element has failed and is leaking current to earth (element ruptured, water got in). If it's an RCD/ELCB tripping, that's an earth-leakage fault — i.e. current is finding a path it shouldn't, which is a genuine shock risk in a wet area.
What to do: switch that heater's isolator off and leave it off. Get a licensed electrician to test the element and its insulation resistance; a failed element is a cheap, common replacement. The reason it's fine when you don't use hot water is that the faulty element only draws current when heating. Please treat this as a real fault, not a nuisance trip.
Switched the heater isolator off as you said and left the rest of the flat on. Electrician confirmed a failed element today. Replaced, no more tripping. Scary how I nearly just kept resetting it 😅
Worth adding for anyone landing here: if it's the RCD/earth-leakage breaker tripping (not just the MCB overloading), there's a fuller thread on why an RCD keeps tripping and how to find the leaking appliance. A water heater whose element has started leaking to earth is a classic cause — and the key point is to trace and fix it, never bypass the breaker, because it's protecting you from a shock.
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