A circuit breaker that trips now and then is annoying. A circuit breaker that keeps tripping is a warning, and it is worth understanding what is behind it before you reset it for the tenth time.
The good news is that, by tripping, the breaker is doing its job: cutting the current before heat can damage the cabling or start a fire. The breaker is never the problem. The problem is whatever is forcing it to act.
The most common causes
Circuit overload. This is cause number one. Too many appliances drawing power at the same time on the same circuit, for example a microwave, a toaster and a kettle on the same kitchen worktop. The breaker holds for a few seconds and then cuts.
Short circuit. When two conductors touch, the current rises sharply and the cut is immediate. It usually comes with a crack, a burning smell or a dark mark on a socket or plug.
Earth leakage. Here it is normally the RCD that trips, not the ordinary breaker. It means current is escaping along a path it should not: damp in a junction box, a water heater with a damaged element, a faulty washing machine.
A faulty appliance. Often the culprit is a single device. Fridges, washing machines and water heaters are the usual suspects, especially when the trip always happens at the same time of day or whenever that appliance starts up.
An undersized or ageing installation. Homes with old wiring were designed for a fraction of today's consumption. If you have added air conditioning, an induction hob or an electric car charger without reviewing the consumer unit, tripping is the natural consequence.
The breaker reaching the end of its life. It happens: a breaker with many years and many trips behind it can become sensitive and start acting with no real cause. It is the least common cause, and the one to assume only after ruling out all the others.
What you can safely check
There are three things you can do without any risk.
- Notice the pattern. Does it trip at the same time every day? Whenever you switch on a particular appliance? Only when it rains? That information is gold for the electrician and shortens the repair.
- Ease the load. Switch off the appliances on that circuit, reset the breaker and switch them back on one by one, with pauses between them. If the trip always returns with the same appliance, you have found the culprit.
- Test the RCD. RCDs have a test button, usually marked "T". When you press it, they should trip. If they do not, the protection for people is not working, and that is a reason to call a professional without delay.
This article is for information only and does not replace assessment by an electrician. Do not open the consumer unit or work on wiring.
What you should not do
Never force the repeated reset of a breaker that trips again immediately: you are pushing against a protection that has detected a real problem. And under no circumstances replace a breaker with a higher amperage one "to stop it tripping". That is the equivalent of ripping out the smoke detector because it is beeping. The breaker is sized to the cable cross section of that circuit; a bigger breaker lets the cables heat up unprotected.
Opening the consumer unit and working on connections is also not a DIY job. In Portugal, work on electrical installations must be carried out by qualified, registered technicians and companies, and current legislation defines who may carry out the work and the safety rules that apply.
When to call an electrician
Ask for a professional assessment if:
- the tripping repeats with no obvious cause
- there is a burning smell or hot sockets
- the RCD does not trip when tested
- the consumer unit still has old fuses instead of breakers
- you have added higher consumption equipment since the installation was last reviewed
A good electrician can measure the real consumption of each circuit, isolate leakage with proper equipment and tell you whether the problem is solved with a one off repair or whether the consumer unit needs to be rethought, with no blind swaps.
Need help?
At LumineLab we handle electrical faults in Lisbon, Cascais and Estoril, with on site diagnosis and a no obligation quote. If your circuit breaker keeps tripping, talk to us on WhatsApp or fill in the form on the site. We usually reply within 24 hours.