A switch in my fuse box has tripped, and won’t go back on.

It is a switch called ‘RCD Protected’, and is separate from the different area-specific socket fuses. In any case, when I switch it back on, it stays on for one second the goes off again.

There is nothing plugged that is not normally plugged in.

Any ideas as to what I can do?

is the entire system going off when it trips?

Unplug everything you can including the washing machine etc then try switching it on. If it still trips call an electrician. If it doesn’t plug things back in until it trips – then you have the guilty party

There is nothing plugged that is not normally plugged in.

I’d start by unplugging everything and seeing if it can then be reset. If it can I’d plug things back in one at a time and see what trips it.

…so what tj said then, but a minute slower.

The above advice is good, but as an extra question, do you have any external power (to a shed/garage or for Christmas lights etc). The RCD protected bit ‘could’ be for those so if the rest of the house is OK, think about what power could have been added after the property was built/wired.

Mine is for a Power Shower so it may not be external

Before you start unplugging absolutely everything, narrow your search by first switchlng off the rcd then all the circuit breakers in the consumer unit / fuse box. Switch the rcd back on then switch on each circuit breaker one at a time. When the rcd trips again, investigate the last circuit you switched on. Might save you a bit of time and effort.

Probably the toaster.

Go to the Pub?

If after everything is in unplugged….. this includes switching off washing machines and dishwashers etc it still won’t set you have an earth neutral fault. This could be anywhere and you will need to start taking neutrals out of the neutral bar in the consumer unit one by one and resetting the rcd until you find the culprit (this is ideally done by a sparks)

First check what circuits (down sockets, up sockets, down lights, up lights, boiler, shower) are live and which ones are dead. That might narrow down your search. If it’s all of them you need to look in a different place than if it’s just one.

Cooker.

RCD stands for Residual Current Device.

It sits across the Live and Neutral wires in your consumer unit (used to be called the “fuse box” and it monitors where the current is flowing too. Under normal conditions, every amp that flows out along the Live wire is expected to come back down the Neutral wire, ie sum to zero. When an earth leakage fault occurs, ie something becoming Live that shouldn’t be, and hence current flows out to Earth, instead of Neutral, then the RCD trips (should be within around 30ms) to try to prevent the risk of electric shock. This device is in-addition to the normal fuses, or these days circuit breakers, that open the circuit is excessive current flows (but flows the right way around the circuit, ie Live to Neutral.

So, if your RCD is tripping immediately then:

1) the RCD is faulty – not that un-common, they have sensitive relays and electrical / mechanical bits inside.

2) Current is leaking out to earth (as little as 10mA possibly to trip a typical 30mA RCD)

I had a friend who’s RCD would trip after heavy rain, and eventually, after much searching, they found a hole in a cable in the shed onto which rain water would drip, but only after very heavy rain, and the current was using that water as an escape route to Earth, hence the RCD tripping

As others have said, it’s a matter of isolating each circuit in turn to find the one that trips the RCD, bearing in mind the RCD itself could be faulty!

I’ll twist on Cooker/oven as well (only cos that’s what it was for me)

what scoob67 says. Start with all of the main breakers off and switch them on one by one to work out which circuit it is. if you have an electric immersion heater, and undersink heater or a clothes iron these are the usual culprits

The amount of leakage to trip an RCD is small 10 or 30MA . Something to do with current and heart attack survival after a lecy shock.
Could be a laptop charger or even a lightbulb . If you have the same weather as down south it may well be water related

Do not ignore it. My mate was nearly killed in a house fire because we ignored a shock from a light swtich, which was water leaking through the roof and finding its way into the lighting circuit.
The cold water tank nearly killed him as it crshed into his bedroom after the fire weakened the joists

Anything that has a heater element for water is normally the culprit in our house. Or a large sultana or raisin in the toaster!

Yesterday I saw an immersion heater that had been in very hard water and had got clogged, overheated and then expanded in places and short-circuited through accumulated calcium to Earth. T’was a mess.

Yes, plenty of things are wired into place and you can’t unplug.

Which switch is it that doesn’t stay on? What doesn’t work in the house when it’s off?

Happened to me last week.

My box has seperate switches for 7 different circuits, then one bigger rcd switchwhich trips if any of them do.

As above, isolate which circuit is tripping the rcd. Then on that circuit unplug and unfuse (the non-switcable wall plates should have a pull out fuse holder) everything.

If it still trips, it’s a wiring issue so electrician.

If not you need to sequentially put things back on till you find the faulty socket/fuse/appliance.

What doesn’t work in the house when it’s off?

Judging by the OP’s lack of response – his wifi router.

Ha ha! No, the OP was out making up for lost riding this morning!

Anyway, I’ll ask Mrs SR what she was able to locate and let you know.

Cooker.

Joe Cooker?

It’s happened on two separate, unrelated occasions in our house. On one occasion it was a kettle. On the other, the cooker. The kettle was a tricky one to pin down because it wouldn’t always trip straight away. No electrician involved – we just used a process of elimination as described by others. Did need a service engineer callout for the cooker though (warranty job).

mine was down to a faulty dishwasher…