RCD (Residual Current Device)

Why does my RCD trip when I turn on my electric shower?

The shower unit has a fault — usually a failed heating element or moisture ingress. Turn it off at the isolator switch and call an electrician.

Why does my RCD trip when I use my dishwasher?

Your dishwasher has a fault — usually a failing heating element or pump motor. Stop using it and have it checked by an appliance engineer.

Why does my washing machine keep tripping the RCD?

Your washing machine has developed an electrical fault — usually a failing heating element or motor. Stop using it and have it tested or repaired.

What does it mean when only half my house loses power?

You have a split-load consumer unit with two RCDs — one has tripped. Reset the tripped RCD and investigate which appliance or circuit caused it.

How do I reset my RCD after it trips?

Switch the tripped RCD lever firmly upward to reset it. If it will not reset or trips again immediately, do not force it — the fault is still present.

Can I replace my RCD myself?

No. Replacing an RCD requires working inside the consumer unit, which contains live parts that cannot be made safe without isolating the meter — that requires a qualified electrician.

My RCD will not reset — what should I do?

The fault causing it to trip is still present. Switch off all circuits under it, try resetting, then switch circuits back on one at a time to find the problem.

How do I find which appliance is tripping my RCD?

Unplug everything, reset the RCD, then plug appliances back in one at a time. The one that causes the trip is the faulty appliance.

Can I add an RCD to an old fuse board?

In most cases, yes — a plug-in or inline RCD adaptor can add protection to specific circuits, but the proper solution is a full consumer unit upgrade.

Does my RCD need to be tested and how often?

Yes — press the test button every 6 months. The RCD should trip immediately. If it does not, call an electrician.

Why does my RCD trip when it rains?

Rain-triggered RCD tripping usually means water is getting into an outdoor socket, light fitting, or underground cable, creating a leakage path to earth.

Why does my outdoor socket keep tripping the RCD?

Moisture has entered the socket or its supply cable. Outdoor sockets must be IP66 rated. Do not use it until an electrician has checked it.

Why does my RCD trip when I switch on a light?

The light fitting or its wiring has a fault — usually a damaged cable, failed lamp, or moisture in an outdoor fitting. Switch the light off at the wall and call an electrician.

Why does my RCD trip in the middle of the night?

Usually caused by a fridge, freezer, or immersion heater switching on automatically. The element may be developing a fault that only appears under load.

Why does my RCD trip with nothing plugged in?

The fault is in the fixed wiring itself, not an appliance. Do not keep resetting it — you need an electrician to test the cables and find the fault.

Why does my RCD trip when it rains?

Rainwater is getting into an outdoor light, socket, or cable connection, causing earth leakage. An electrician needs to find and seal the entry point.

Why does my RCD keep tripping?

Usually caused by a faulty appliance or moisture in a circuit. Unplug appliances one by one to isolate the fault.

What is the difference between Type AC and Type A RCDs?

Type AC only detects sinusoidal AC faults. Type A also detects pulsating DC faults — required for modern appliances like washing machines, EV chargers, and solar inverters.

What is the difference between an RCD and an RCBO?

An RCD protects multiple circuits together. An RCBO combines RCD and circuit breaker protection in one device for a single circuit.

Can I have an RCD on just one circuit?

Yes — an RCBO combines an MCB and RCD in one device and protects a single circuit. This is the best solution for problem circuits.

Does my garage need RCD protection?

Yes — any socket circuit that could be used to supply equipment outdoors must have 30mA RCD protection. This includes garage sockets.

Is it dangerous to keep resetting my RCD?

Yes. The RCD is tripping for a reason — it is detecting a fault. Repeatedly resetting it without finding the cause is dangerous.

How long should an RCD take to trip?

A 30mA RCD must trip within 300ms at its rated current, and within 40ms at five times its rated current (150mA).

How do I test my RCD?

Press the Test button on your RCD — it should trip immediately. Reset it after. Do this every 6 months to confirm it's working.

What is the difference between an RCD and an RCBO?

An RCD protects multiple circuits but trips them all together. An RCBO protects one circuit individually — it combines RCD and MCB in a single device.

What is an RCD and how does it work?

An RCD (Residual Current Device) is a safety switch that cuts power within milliseconds if it detects electricity leaking to earth — protecting you from electric shock.