RCD keeps tripping at night or every few hours

You wake up and the clocks are flashing. The freezer has been off for hours. You reset the RCD and everything seems fine until it happens again. A trip that comes and goes like this is harder to track than one that happens every time you switch something on, but there is nearly always a pattern.

What an RCD is reacting to

An RCD (residual current device) compares the current going out on the live wire with the current coming back on the neutral. If some goes missing, it has leaked somewhere, usually to earth. When the leak reaches the trip level, the RCD cuts the power.

It does not need a big fault. Small leaks from several sources can add up. That is why an RCD can trip at random. It might be sitting just under its limit all day, and then one more appliance starts up and pushes it over.

Start a trip log

Before you do anything else, keep a simple record for a few days. Write down:

• the time you found it tripped, and the time it last worked
• the weather (dry, wet, cold)
• what was running or on a timer
• which RCD or switch was down

Patterns show up fast.

Pattern	Likely suspects
Trips in the early hours	Immersion heater on a timer, storage heaters, fridge freezer defrost, washing machine on a delay timer
Trips every few hours, day and night	Fridge freezer defrost cycle, heating pump, dehumidifier
Trips at dusk	Outside lights on a sensor or timer
Trips when it rains or after a cold night	Water or condensation in outside fittings, garden sockets, a garage supply
Trips in the morning when showers start	Electric shower, bathroom extractor fan, wet room fittings
No pattern at all	Several small leaks adding up, or a faulty RCD

Check the timed loads

Immersion heaters. Many London homes with older hot water cylinders have an immersion heater on a timer. When the element ages, its outer sheath can let water reach the heating wire inside, and current leaks to earth. It trips when the timer switches it on, often overnight. Switch the immersion off at its own switch for a few nights and see if the trips stop.

Fridge freezers. Frost free models have a small heater that runs every few hours to melt ice off the cooling coil. If that heater or its wiring has a fault, the RCD trips during defrost. To test it, move the food to a cool box or a neighbour’s freezer and leave the fridge freezer unplugged for a night or two. If the trips stop, you have found the cause.

Heating. Boilers, pumps and controls usually run from a fused spur. Water leaks from radiators or pipes onto wiring can cause trips when the heating comes on.

Outside lights. A light that switches on at dusk and trips the RCD soon after is a strong clue. See our guide to electrics that trip when it rains.

Hounslow and west London homes

Hounslow has a mix of housing that brings its own causes. According to the VOA council tax stock of properties, 28.5% of homes in the borough were built between 1919 and 1939, and 20.3% from 2000 onwards. Almost half, 49.2%, are flats.

In the 1930s semis of Hounslow, Isleworth and Feltham, you often find an older immersion cylinder in the airing cupboard, extensions wired at different times and garden outbuildings fed by long cables. In Chiswick’s Victorian and Edwardian houses, kitchens and bathrooms have often been redone several times, each adding more appliances to the same RCD. In the newer Brentford flats, the consumer units are modern but crowded, with many appliances on few circuits.

Remember that Hounslow, like Ealing, is served by SSEN rather than UK Power Networks, according to the Mayor’s answer to the London Assembly. If your whole street loses power overnight, that is a network fault, not your RCD. Call 105. Our guide to power cuts in Ealing and Hounslow explains more.

Why a new consumer unit can seem to trip more

If you have recently had a new consumer unit fitted and the trips started afterwards, the new board is not necessarily faulty. Older fuse boxes often had no RCD protection at all, or only on some circuits. When modern RCD protection goes on, it detects leaks that were always there. The trips are real faults showing up for the first time.

Current wiring rules are set out in BS 7671:2018+A4:2026, which since 15 October 2026 is the only current version of the standard. Modern designs often use RCBOs, which combine a breaker and an RCD for each circuit. With RCBOs, one leaky appliance only takes out its own circuit, not half the house.

What an electrician does

When we visit for an RCD tripping problem, the work usually runs like this:

1. Look at your trip log and the consumer unit layout.
2. Test the RCD itself for correct operation.
3. Measure insulation resistance on each circuit, which shows how much each one leaks.
4. Measure leakage from fixed appliances such as immersion heaters and showers.
5. Isolate the faulty circuit or appliance so the rest of your home stays on.
6. Explain what was found and quote for the repair.

Intermittent faults can take more than one visit to pin down, especially if they are linked to weather. A clear trip log shortens that a lot.

Keep safe in the meantime

• Do not tape or wedge the RCD on.
• Move frozen food to a neighbour’s freezer if the trips are frequent.
• Keep a torch by the bed.
• If you smell burning or hear crackling from the consumer unit, switch off at the main switch if safe and call an electrician.

If you are in Hounslow or Chiswick, start the log tonight. Three nights of times will tell an electrician more than an hour of guessing.