It is usually the evening, and usually mid-something — mid-cooking, mid-shower, mid-film. Everything goes off. You find a torch, you find the cupboard with the board in it, and you are looking at a row of switches wondering which one matters and whether touching it is sensible. This page is for that moment. It sets out what you can safely do yourself, what the board is telling you, and the point at which the right answer is to stop and get an electrician.
The short version: resetting a tripped switch is a normal thing for a householder to do. Working out which appliance is causing it is also fine and genuinely useful. Taking the cover off the board is not, ever. That line is not us being precious — it is where the risk changes from inconvenience to injury.
First question: is it only you?
Before touching anything, look outside your own front door. If the communal landing lights are out too, or the neighbours are also in the dark, or the street lighting has gone, then the problem is not in your flat and nothing you do at your board will fix it. That is a supply matter for the distribution network operator, or a building matter for the freeholder or managing agent — and knowing which of the two it is saves you paying for an electrician to tell you it was never yours.
In a mansion block the picture can be muddier. Sometimes half a building goes off because something has failed in the communal intake or a riser, which is the freeholder's territory rather than yours. If your flat is dark but your board shows nothing tripped at all — everything still up, no switch in the off position — that is a strong hint that the problem is upstream of your board rather than inside it. Check your meter and, if you have a prepayment or smart meter, check it has not simply run out of credit. It happens more often than people admit, and it is an expensive call-out to discover it.
What the board is actually telling you
Look at which device has operated, because each one means something different.
- One small breaker off, everything else on. An overload or a fault confined to that one circuit. The most contained situation.
- A wider switch off, taking several circuits with it. Usually an RCD. It has detected current leaking to earth somewhere in the group it protects. The fault is on one circuit; the effect is on all of them.
- The main switch off. Everything is dead. Something significant has happened, or somebody has knocked it.
- Nothing tripped, but no power. As above — look upstream, at the meter and the supply, not at the board.
Photograph the board before you change anything. It sounds fussy; it is the single most useful thing you can do. It records exactly which device operated, which is information that disappears the moment you start resetting things and which an electrician would otherwise have to reconstruct.
The safe sequence
Assuming there is no smell of burning, nothing is hot, nothing is wet and nobody has had a shock — see the next section if any of that applies — this is the sequence a householder can reasonably follow.
One. Work out what the affected circuit covers, and unplug everything on it. Not switch off at the socket — unplug. If it is the whole flat, unplug generously: kettle, toaster, washing machine, dishwasher, dryer, TV, chargers, that dehumidifier in the spare room.
Two. Reset the device that tripped. Push it firmly to off first, then to on. Some devices will not reset unless they are fully off first, which is why people conclude a board is broken when it is not.
Three. If it holds, plug things back in one at a time, leaving a minute or so between each. When it trips again, you have found your appliance. If it is the tumble dryer or an old kettle, the electrician you need may in fact be an appliance engineer, or a shop.
Four. If it holds with everything back on, the likeliest explanation is a single appliance with a transient fault, or a cumulative-leakage problem — see below. Note the date. If it happens again, you have a pattern, and a pattern is worth money to whoever diagnoses it.
Five. If it will not reset with everything unplugged, stop. The fault is in the fixed wiring, and that is not householder territory. This is where proper fault finding starts.
Stop and call someone now if
Some symptoms are not a puzzle to work through. Stop and get an electrician if you notice a smell of burning or hot plastic anywhere near the board, sockets or switches; if the board or any accessory is warm, discoloured or scorched; if there is any buzzing or crackling; if anyone has felt a shock or a tingle from a tap, an appliance or a switch; if water is getting anywhere near electrical equipment; or if a device trips again immediately every time it is reset. In the last case, resetting repeatedly is not a strategy — the device is doing its job, and forcing it is how a fault becomes a fire.
If there is water involved — a leak from the flat above finding a light fitting is a genuinely common event in mansion blocks — treat it as both a plumbing and an electrical problem. Do not switch things on to test them. Our plumbing service and our electricians work together on exactly that combination, because fixing the leak and not the wiring, or the wiring and not the leak, solves half a problem.
Why it trips at three in the morning
This is the classic, and it drives people to despair. Nothing is on, everybody is asleep, and the RCD trips anyway. The explanations are usually mundane. Something is running that you do not think of as running: an immersion heater on a timer, heating coming on, a fridge or freezer cycling, a dehumidifier, an outside or communal light on a photocell. If the trip happens at the same time every night, look for a timer before looking for a ghost.
The other explanation is cumulative earth leakage. Every appliance leaks a tiny amount of current to earth by design. Add up a dishwasher, a washing machine, a TV, a set of LED drivers and an old immersion and the total may sit just under the RCD's threshold most of the time and just over it when the weather is damp or one more thing switches on. Nothing is faulty. The board is simply arranged so that all the leakage lands on one device — which is a design-generation problem, not a fault, and is one of the situations where a board with individual protection per circuit is the real fix. Our guide to consumer unit upgrades and regulations explains that, and what drives the cost covers the next step.
The older-flat version of the problem
In the period conversions of W2 and W9 and the mansion blocks of NW8, there is a further layer. Older circuits sometimes have degraded insulation that leaks slightly when warm, so the flat behaves perfectly all summer and starts tripping when the heating goes on. Some old lighting circuits borrow a neutral from a neighbouring circuit, which produces trips that appear to make no sense until someone tests properly. And there is rarely a loft or accessible underfloor void to inspect from, so the diagnosis is done from the board outwards rather than by looking. None of this can be resolved by resetting switches, and none of it is your fault.
What an electrician will do that you cannot
Safe isolation and proving dead — the discipline of making certain a circuit is off before touching it — comes first, and it is the part that householders skip. After that: measuring insulation resistance to find degrading cable, measuring leakage to find which circuit or appliance is contributing what, splitting the installation to narrow the search, and checking earthing and bonding, which in older flats is frequently missing or incomplete without anyone noticing. Electrical work in dwellings falls under Building Regulations Part P and installations are tested to BS 7671; the work should be certified.
What you can hand over that shortens the visit: the photo of the board, which device tripped, what was running, whether it is time-related, what you unplugged, and what you have already ruled out. It is not unusual for that information alone to halve the time.
What we do about it
Our electrical work starts from £80 with set prices published on the electrical page. For a tripping fault, we diagnose first and give you a fixed price to fix whatever we find before we fix it, so the repair is not an open-ended meter running. If the finding is that the board's arrangement is the problem rather than a fault, we will say so and explain the options rather than simply selling you the bigger job.
In blocks we deal with porters, booked access and restricted working hours as a matter of course — around Little Venice and Maida Vale particularly, where meters and intakes commonly sit in communal cupboards controlled by the building rather than by you. For landlords and portfolios, repeated tripping is nearly always a deferred-maintenance signal, and it is cheaper to deal with through planned maintenance than through a series of evening call-outs. Our Little Venice electrician page covers local work in W9.
If you are standing at the board now and it will not hold, send us the details — a photo of the board and a line about what happened — and we will tell you what we can see.