Insights
Why Your Safety Switch Keeps Tripping and What It's Telling You
A safety switch that keeps tripping is annoying, but it's also doing exactly the job it was installed to do. Before you get frustrated and start hunting for a way to stop it, it helps to understand what it's protecting you from and how to track down the cause.
First, know the difference between the switches on your board. A circuit breaker trips when a circuit draws too much current, protecting the wiring from overheating. An RCD, the safety switch, does something different. It constantly compares the current flowing out against the current flowing back, and if even a small amount is leaking to earth it cuts the power in a fraction of a second. That leakage is what would otherwise flow through a person who touches a fault, which is why an RCD is the thing standing between you and a fatal shock.
So when an RCD trips, it's usually telling you that current is escaping somewhere it shouldn't. The most common cause is a faulty appliance. Worn elements in kettles, toasters, and old heaters are frequent offenders, and so is anything that's let moisture in, like an outdoor tool or a leaky appliance.
The good news is you can often find the culprit yourself. Start by unplugging everything on the affected circuit. Reset the RCD. If it holds, plug your appliances back in one at a time, giving each a moment, until the switch trips again. The last thing you plugged in is very likely your faulty appliance. Stop using it and get it repaired or replaced.
There are times to stop testing and call a registered electrician. If the RCD trips immediately with nothing plugged in, the fault is in the fixed wiring, not an appliance, and that needs a professional to find. If it trips repeatedly even after you've removed the suspect appliance, or trips at random with no pattern, there may be a wiring fault, moisture in a circuit, or a failing RCD itself. And if you ever smell burning or see scorch marks near the board or an outlet, treat it as urgent.
The one thing you should never do is try to defeat the safety switch or keep resetting it over and over to force the power to stay on. The RCD is tripping because it has detected a genuine fault, and bypassing it removes the protection that could save your life. A nuisance trip is far better than the alternative.
In New Zealand this kind of fault-finding in the fixed wiring is work for a registered electrician. If you've done the appliance test and the problem is still there, that's the point to get someone qualified in. They can use proper test gear to locate the fault safely and put it right, rather than leaving you guessing.