Do not keep resetting it
If a breaker trips again the instant you push it back up, leave it off. It is tripping because there is a fault on that circuit, and every reset puts current back through the fault. Switch off the circuit, or the main switch if you are not sure which one, and get someone to look at it. That is the same advice on our emergency electrician page, and it is the one rule in this article that matters most.
If it trips now and then, with hours or days in between, you have time to work out why. That is what the rest of this is for.
Which switch is tripping
Open the consumer unit (the fuse box) and look at which switch has dropped. There are two kinds, and they trip for different reasons.
A circuit breaker, or MCB, is one of the row of small switches, each labelled for a circuit: downstairs sockets, upstairs lights, cooker, shower. It trips when too much current flows through that one circuit, either because too many things are plugged in or because something has shorted. An MCB tripping tells you which circuit has the problem.
An RCD is the wider switch, usually with a test button marked T, that protects a group of circuits or the whole board. It trips when current is leaking to earth, which is what happens when a live part touches something it should not, including water or a person. An RCD tripping tells you there is a leak somewhere on everything it covers, which can be half the house.
Newer boards use RCBOs, one per circuit, which do both jobs and take you straight to the circuit at fault. If your board has a single RCD covering everything, a small fault anywhere takes out half the house, and that is one of the reasons boards get replaced.
The checks you can do yourself
Do these with the power off at the tripped switch. Nothing here involves opening anything or touching a wire.
- Unplug everything on the affected circuit. Every socket, including the ones behind furniture, the fridge and the washing machine. Switch off any fixed appliance with its own switch, such as the cooker or the shower.
- Reset the switch. If it holds with everything unplugged, the wiring is probably fine and one of the appliances is the fault.
- Plug things back in one at a time, switching each one on and giving it a minute. When the switch trips again, the last thing you plugged in is your suspect.
- Test the suspect somewhere else. Plug it into a socket on a different circuit. If that trips too, the appliance is the fault, and it goes in the bin or to a repairer. If it does not, the original socket or the cable to it may be the problem, and that is our job.
- If it trips with everything unplugged, the fault is in the wiring, a fixed fitting or the board itself. Leave the circuit off and ring us.
Do not open the consumer unit, do not take the face off a socket, and do not put a bigger fuse or a bit of wire in to stop it tripping.
The usual causes
A faulty appliance. The most common cause by far. Heating elements are the usual offenders: kettles, tumble dryers, ovens, irons, immersion heaters and electric showers all have an element that can crack or get damp and leak current to earth. That is why an oven trips the RCD when it gets to temperature, or a tumble dryer trips it twenty minutes in. Motors and old fridges do it too.
Too much on one circuit. A kitchen circuit running the kettle, the toaster, the microwave and a heater at once can draw more than its breaker allows. This trips the MCB, and it happens at the same time of day. The fix is spreading the load, or in a kitchen that has grown since the house was wired, a new circuit.
Water. Outside lights, garden sockets, a shed supply, a hot tub, or the light in a damp bathroom. Water bridges live to earth and the RCD does its job. If your electrics trip when it rains, the fault is almost always outside or in the loft, and you will not find it by unplugging things indoors.
Something you did not know was on. If the electrics trip when everything is off, something is still drawing current: a fridge freezer, the boiler, an immersion heater on a timer, outside lights on a sensor, the doorbell transformer, or the electric shower’s pull cord left on. One of those has a fault. If every one of those is off and it still trips, the wiring itself is leaking and needs testing.
A damaged cable. A nail or screw through a cable behind a wall, a cable chewed in the loft, or a joint that has come loose over the years. These often show up as a trip that gets more frequent over weeks.
Old wiring or an old board. Rubber or fabric insulated cable from the 1960s and before crumbles and lets current leak. A board with one RCD for the whole house will trip on the sum of lots of small leaks that no single appliance would cause. Both are fixed by replacing what has worn out. Resetting the switch does nothing for either.
A worn out breaker. Rarely, the breaker itself is the fault. An MCB that has tripped many times can weaken and trip below its rating. We test the breaker before we blame the circuit.
When tripping means something bigger
A single faulty kettle is a trip to the shop. These are the patterns that mean the installation needs looking at:
- It trips with everything unplugged. The fault is fixed wiring, a fitting or the board.
- It trips more often each week. A damaged cable or a failing connection is getting worse.
- The board has no RCD at all, or one RCD for the whole house, or wooden back, cast iron switches or wire fuses. It is past its time, and a new consumer unit with RCBOs will stop one small fault taking out half the house and tell you exactly which circuit is at fault next time.
- The house has not been rewired since the 1970s. Tripping is one of the signs on our rewires page, alongside warm sockets, flickering lights and a house running on extension leads.
- You are a landlord and the tenant reports it. Tripping on a rental is an EICR question as much as a repair one, because the report will find the cause and give you the paperwork.
In each of those cases we test the circuit rather than guess. Insulation resistance and earth leakage tests find the fault in a way that unplugging things cannot, and the fix is quoted before we start.
When to ring straight away
Some tripping does not wait until morning. Ring us now if there is a burning smell, scorching or browning around a socket, switch or the board, if the trip happened with a bang or a flash, if water has got into the consumer unit, or if you cannot reset the switch at all. Turn the main switch off if you can do it safely, and send a photo of the board on WhatsApp so we know what we are coming to. Our emergency call out covers Leeds 24 hours a day, and the price is fixed before we set off.
