In short
A safety switch (RCD) trips when it detects electricity leaking to earth, usually through a faulty appliance, water in an outdoor fitting or damaged wiring. Unplug everything on the tripped circuit, reset the switch once, then plug things back in one at a time to find the culprit. If it trips with nothing plugged in, or will not reset, stop and call a licensed electrician.
If you would rather have it checked, Ambient Electrical offers safety switch installation in Sydney's Eastern Suburbs.
What a safety switch actually does
A safety switch, also called a residual current device or RCD, watches the current going out on the active wire and coming back on the neutral. If some of it is leaking away to earth, which is what happens when current flows through a person, it turns the power off in a fraction of a second.
Household safety switches trip when the leakage reaches a harmful level, typically 30 milliamps or less. A switch that trips is usually doing its job: something on that circuit is leaking.
How to find what is tripping it
Most tripping comes from one appliance. This is the method Peter recommends for narrowing it down safely:
- Unplug the appliances on the circuits the safety switch protects, or switch off their circuit breakers at the switchboard.
- Reset the safety switch once by pushing it back up to on.
- Turn the circuit breakers back on one at a time, then plug appliances back in one at a time.
- When the safety switch trips again, the last circuit or appliance you turned on is the likely cause. Leave it unplugged or switched off and have it checked.
Reset it once per step. Repeatedly resetting a switch that trips the instant you push it up means there is a real fault, and the switch is protecting you from it.
It trips with nothing plugged in
If the safety switch trips with every appliance unplugged, the fault is in something permanently wired: a hot water system, oven, cooktop, pool pump, outdoor or garden lighting, an exhaust fan, or the wiring itself.
That needs an electrician with an insulation resistance tester to find which circuit and which part is leaking. It is not something to chase with the covers off.
It trips at night, or after rain
Tripping after rain almost always means water is getting in somewhere outdoors: a weathered power point, a garden or step light, a shed circuit, pool equipment, or a damaged underground cable. Salt air near the beach speeds up the corrosion that lets it in.
Tripping at night often lines up with something that switches on by itself, such as an off-peak hot water system, a timer, a heater or an appliance on a delayed start. Noting the time it trips is useful information for the electrician.
Nuisance tripping
A safety switch can occasionally trip with less than its rated leakage, from a voltage surge, electrical noise on the installation, or several appliances each leaking a little onto the same switch. Appliances with heating elements, like kettles, heaters, ovens and washing machines, are common contributors.
Newer switchboards spread circuits across several safety switches, so one leaking appliance cannot black out the whole house. If a single old safety switch covers everything, that is worth fixing.
Testing your safety switch
The NSW Government recommends testing safety switches twice a year: press the TEST button on each one and it should switch off straight away. Push it back to on and you are done. If it does not trip, it is not protecting you and needs replacing.
An electrician tests more thoroughly with a multifunction tester, which applies a controlled fault current and measures how quickly the switch operates.
When to call an electrician
- It trips instantly with everything unplugged or switched off
- It will not reset at all
- It trips again and again and you cannot find the appliance
- There is a burning smell, scorch marks, or the switchboard feels warm
- Your home has old ceramic fuses and no safety switches at all
These life-saving devices can be easily retrofitted to all electrical installations. Safety Switches can be installed at the switchboard protecting all light and power circuits or anywhere on a power circuit protecting that point and beyond.
Sources
- NSW Government: Electrical safety in the home
- SafeWork NSW: Managing electrical risks in the workplace, code of practice (PDF)
Ambient Electrical is an electrician in Bronte, Waverley and Bondi, and works across Sydney's Eastern Suburbs.
