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.

Is it illegal to have no RCD protection?

It is not automatically illegal for a homeowner to have no RCD protection in an existing installation, but it is a serious safety breach. New installations and significant alterations must comply with BS 7671 18th Edition (Amendment 2), which requires RCD protection for most circuits. An EICR will likely code missing RCD protection as C2 (potentially dangerous). You should have a qualified electrician assess your installation immediately. Landlords have a legal duty under the Electrical Safety Standards Regulations 2020 to ensure tenant properties meet current safety standards.

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.

Why is my RCD tripping but the electrician can't find the fault?

An RCD that trips but leaves electricians baffled usually has an intermittent or low-level earth leakage fault — often from ageing appliances, damp wiring, or cumulative leakage across multiple circuits. Ask your electrician to perform a full insulation resistance test on each circuit individually, check every connected appliance, and consider a time-of-day pattern. If it only trips at night or in wet weather, suspect moisture ingress. Do not ignore repeated tripping — it indicates a genuine fault that could cause electric shock or fire.

Why does my RCD trip intermittently with no pattern?

An intermittent RCD trip with no obvious pattern is most commonly caused by gradual insulation breakdown, nuisance tripping from accumulated earth leakage across multiple circuits, or a failing appliance with a temperature-dependent fault. Start by unplugging all appliances and monitoring the RCD. If it holds, reconnect items one at a time to identify the culprit. Do not repeatedly reset a tripping RCD without investigation — persistent tripping indicates a genuine fault that requires a qualified electrician to test and resolve safely.

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.

Why does my EV charger trip the RCD?

Your EV charger trips the RCD most commonly due to high earth leakage current from the charger's internal EMC filter capacitors — this is normal but can exceed your RCD's trip threshold. First, check whether the dedicated EV circuit uses a Type A or Type B RCD, as many EV chargers require a Type B (or Type A + DC detection device). If a standard Type AC RCD is fitted, it must be upgraded. Call a qualified electrician if the fault persists — do not repeatedly reset and retry.

Why does my outside socket trip the RCD?

Your outside socket trips the RCD most commonly because of moisture ingress causing an earth leakage fault. Water in the socket, damaged cable insulation, or a faulty appliance plugged in are the usual culprits. Start by unplugging everything from the outdoor socket and try resetting the RCD — if it holds, the problem is a connected appliance. If it still trips with nothing plugged in, the wiring or socket itself has a fault and you must call a qualified electrician. Do not bypass or tape up a tripping RCD — it exists to protect you from electrocution.

Why does my washing machine trip the RCD?

Your washing machine is most likely tripping the RCD due to a earth leakage fault — water ingress, a failing heating element, or a faulty motor are the most common causes. Start by unplugging the machine and resetting the RCD. If it holds without the machine plugged in, the fault lies in the appliance itself. Do not continue using it until it has been inspected. If the RCD trips with nothing plugged in, call a qualified electrician immediately, as the fault may be in the wiring.

Why does my RCD trip with nothing plugged in?

An RCD tripping with nothing plugged in usually indicates a wiring fault, moisture ingress, or leakage current within the fixed wiring itself — not your appliances. The most common cause is a damaged cable or faulty light fitting allowing current to leak to earth. Reset the RCD; if it trips immediately or repeatedly, stop using that circuit and call a qualified electrician. Do not tape the RCD open or bypass it — it exists to protect you from electric shock and fire.

Why does my RCD trip at night?

Your RCD most likely trips at night due to a faulty appliance switching on automatically — such as a fridge, freezer, or heating system — creating an earth leakage current above 30mA. Start by unplugging appliances on the affected circuit one at a time and resetting the RCD. If it continues tripping with nothing plugged in, the wiring itself may have a fault. Do not repeatedly reset an RCD that keeps tripping — persistent tripping is a safety protection signal and you should call a qualified electrician.

Why does my RCD trip when it rains?

Your RCD trips in rain most likely because moisture has entered an outdoor socket, light fitting, or cable connection, creating a leakage current to earth that triggers the RCD's protection. Check for visibly wet outdoor fittings and switch off circuits serving garden or external equipment. Do not reset and ignore repeated trips — this indicates a real fault. A registered electrician should inspect and test the installation before the circuit is returned to use.

Why won't my RCD reset?

Your RCD won't reset because there is still a fault present on the circuit it protects. The most common cause is a faulty appliance causing an earth leakage current above 30mA. Unplug everything from every socket on the affected circuit, then try resetting the RCD. If it holds, plug appliances back in one at a time to identify the faulty one. If the RCD still won't reset with nothing plugged in, you have a wiring fault and must call a qualified electrician immediately.

Why does my RCD keep tripping?

Your RCD keeps tripping most commonly because of a faulty appliance with a current leakage to earth. Unplug everything on the affected circuit, reset the RCD, then plug appliances back in one at a time to identify the culprit. If the RCD trips with nothing plugged in, or repeatedly trips without an obvious cause, you have a wiring fault and must call a qualified electrician immediately. Never tape or bypass an RCD — it protects you from electrocution.

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 do I know if my RCD is faulty or leaking?

A faulty or leaking RCD can be identified by testing its built-in test button monthly — if it fails to trip, the device is faulty. Signs of a leaking RCD include nuisance tripping without an obvious fault, or circuit breakers tripping unexpectedly. Press the TEST button: it should trip instantly. If it doesn't, replace the RCD immediately and call a qualified electrician. Never ignore a non-tripping RCD — it may fail to protect you from electric shock or fire. A registered electrician can perform a full RCD trip-time test to confirm performance.

How do I test if my RCD is working properly?

Press the TEST button on your RCD — it should trip immediately, cutting power to that circuit. Reset it by flipping the switch back up. If pressing TEST doesn't trip it, or it won't reset afterwards, the RCD is faulty and must be replaced by a qualified electrician. Test your RCD monthly as recommended by manufacturers and BS 7671. Never ignore a failed test — a faulty RCD cannot protect you from electric shock or fire.

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.