Safety Switches (RCDs) Explained: Do You Have One?

A safety switch — properly called a residual current device, or RCD — is one of the most important pieces of electrical safety in any home. It does something a fuse or circuit breaker can’t: it protects people from electric shock.

What it actually does

An RCD constantly monitors the flow of electricity in a circuit. If it detects even a tiny imbalance — the kind that happens when current leaks through a person to earth — it cuts the power in a fraction of a second. That speed is what makes it life-saving.

How it differs from a fuse or breaker

• A fuse or circuit breaker protects the wiring from overload and short circuits, to prevent fires.
• A safety switch (RCD) protects you from electric shock.

They do different jobs, and a home really needs both. Having fuses doesn’t mean you’re protected against shock.

How to check you have one

Look at your switchboard. A safety switch has a test button (usually marked “T” or “Test”). If you can’t see any test buttons, you may not have RCD protection — or only part of the home is covered. Many older homes have switches on only some circuits, or none at all.

Test them regularly

Safety switches should be tested by pressing the test button every few months — the power to that circuit should cut out instantly. If it doesn’t, the switch isn’t working and needs attention. It only takes a moment and it’s the one bit of electrical maintenance every household should do.

Getting them installed

If your home lacks safety switches, a licensed electrician can fit them at the switchboard. On most homes it’s a straightforward job, and it’s hard to think of better value for the protection it provides — particularly for households with kids.