Reading your consumer unit: RCD, breakers, main switch
In a recent consumer unit, three families of protection work together. The main switch, at the top, cuts the whole home. The residual current device (RCD), rated 30 mA, watches for current leaking to earth: it protects people. The circuit breakers, one per circuit, protect the cables against overload and short circuits: kitchen sockets, lighting, oven, washing machine.
Spotting which one tripped already tells you a lot. A single circuit breaker points to an overloaded circuit or a short circuit. The RCD points to a current leak, often a damp or faulty appliance. The main switch points to a global overload or a fault upstream.
- Lever down or in the middle position: the protection has tripped.
- A “test” button identifies the RCD.
- The labels on the panel are your best ally: if they are missing, note one quiet evening what goes off when you switch each line.
The five-step method
It works for a breaker as for an RCD. Take a torch and write down what you do.
- 1. Switch off all the circuit breakers, then reset the RCD or the main switch. If it holds, the fault is on a circuit.
- 2. Switch the circuit breakers back on one by one. The one that trips again points to the circuit at fault.
- 3. On that circuit, unplug every appliance, then reset. If it holds, an appliance is at fault.
- 4. Plug them back in one by one until it trips: you have found the appliance. Do not plug it in again.
- 5. If it trips with the circuit empty, everything unplugged, the fault is in the installation itself: cable, socket, junction box, damp. That is where the electrician comes in.
The most common causes
The symptom points the way: instant tripping, tripping after a few minutes and tripping in the rain do not have the same cause.
- Overload: too many powerful appliances on one line (kettle, oven, hob, hairdryer). The breaker trips after a few minutes of use.
- Short circuit: instant tripping, sometimes with a bang or a smell. Damaged extension lead, melted power strip, faulty appliance.
- Earth leakage: the RCD trips. Washing machine, dishwasher, water heater, outdoor appliance, wet socket, damp junction box after rain.
- Ageing appliance: water heater element, fridge motor, old oven. The fault appears once the appliance warms up.
- Tired installation: worn breaker that trips too early, loose connections that heat up, failing earth.
When not to keep trying
Resetting once is normal. Resetting three times in a row is not: every trip on a real fault heats the weak point a little more.
- Burning smell, warm socket or panel, black marks, crackling: switch off the main breaker and call.
- The RCD trips and no appliance is at fault: the leak is in the installation, do not keep resetting.
- The main switch trips for no apparent reason, or the whole home flickers: the fault may be at the meter or the service connection. Call before touching anything.
- Old panel without an RCD, or with cartridge fuses: the installation does not protect people as it should. A compliance upgrade matters more than a repair.
- After a water leak or flooding: reset nothing before an inspection.
And if it is not your home?
If no breaker has moved and the neighbourhood is dark too, the outage is on the grid: Creos, the grid operator, publishes the network status and a fault-reporting number on its website, and an electrician cannot help. If you alone are in the dark with an untouched panel, the fault may be at the meter or on your service connection: call.
Stopping it from happening again
Most repeated trips come from an installation that has not kept up with how you live: more appliances, more powerful, on the same lines as twenty years ago.
- Spread heavy appliances over different circuits; a dedicated line for the oven, the hob, the washing machine, the EV charger.
- Replace daisy-chained power strips and permanent extension leads with fixed sockets.
- Test the RCD once a month with its “test” button.
- Label the panel.
- Have an installation over twenty years old inspected, and before adding a charger, a heat pump or air conditioning.
How a call-out with All.Electro works
On the phone, we go through this diagnosis with you in a few minutes; sometimes the power comes back without a visit. Otherwise we come out, day and night. The on-site diagnosis costs €60 to €120 depending on the time, stated before we leave, and no work starts without your agreement.
Before you call, have to hand
- What tripped: circuit breaker, RCD or main switch.
- What you have already tried, and what happened.
- The suspect appliance or circuit.
- The approximate age of the panel, and a photo of it.
- Your exact address and a number you can be reached on.
Frequently asked questions
The breaker trips at night when nothing is plugged in
Look for what starts on its own at night: water heater, heating, pump, fridge, outdoor lighting with a motion sensor. An insulation fault on an appliance that starts in cycles is the usual cause.
Can I replace the breaker with a bigger one?
No. The rating protects the cable, not the appliance: a rating that is too high lets an undersized line heat up. If the line is too small, a line is what needs adding.
The RCD trips when it rains
Look outside: terrace socket, garden lighting, gate, junction box, recessed spotlight. Moisture gets in, the leak trips. Dry it out, then seal or replace.
How much does a call-out cost?
The on-site diagnosis costs €60 to €120 depending on the time, stated before we set off. Any work is priced before it starts.
A socket has melted, what should I do?
Switch off the circuit at the panel and do not use the socket again. A melted socket signals a loose connection or an overload: it gets replaced, and the line gets checked.