The RCD: Understanding its purpose and why it trips

Although its activation is a sign that it’s doing its job, it’s not uncommon for the RCD to trip frequently or without an apparent cause, interrupting the electricity supply —something that can lead to inconvenience, confusion, and risks. That’s why here we’ll explain how to prevent unnecessary trips and what to do if it stops working. We’ll also share tips on how to keep your installation in good condition, how to protect your devices and how to keep your home safe.

What is an RCD and why does it trip?

As mentioned above, the RCD is responsible for detecting differences between the current entering and leaving the circuit. If a leak occurs, the RCD cuts the supply to prevent electrical accidents. The most common reasons are:

• Faulty appliances: Worn-out insulation or incorrectly installed equipment (e.g., washing machines, refrigerators or water heaters) may cause current leakage.
• Moisture-prone areas: Placing sockets, cables or installations in damp environments often leads to leaks.
• Momentary overloads: They occur when you plug in and use several large appliances at once, which can create electrical interference.
• Installation issues: Poor grounding, inadequate connections, or old wiring in appliances can lead to insulation problems.
• Overly sensitive RCD: Older models tend to cut power in response to minor current fluctuations.

RCD vs. circuit breaker: Understanding the difference

Distinctly different, yet equally essential. They may look similar and share space in your electrical panel, but the residual current device (RCD) and the circuit breaker (often simply called the ‘breaker’) play two very different roles within your home’s wiring. Each is designed to protect you from specific electrical risks.

The RCD’s job is to protect you against current leakage —preventing situations where electricity might divert through a person or onto conductive metal surfaces. Essentially, it acts fast whenever it detects an imbalance between the incoming and outgoing current.

The circuit breaker is built to safeguard your home’s installation from overloads and short circuits. Whether you’re running too many appliances at once or a fault occurs, it automatically cuts the power to prevent damage, protect your devices and keep your home safe from fire hazards.

What to do when your breaker trips: A safe, step-by-step guide

An RCD that isn’t working properly is a serious electrical safety hazard. If it can’t be reset or keeps tripping:

Check whether the trip is one-off or recurring

If it happens once, it may be due to a temporary fluctuation. However, if it happens frequently, you’ll need to determine whether it’s related to a specific appliance or device (such as when you switch on the washing machine, electric oven, etc.).

Disconnect everything and test the RCD

Turn off all the switches on the electrical panel and unplug appliances and devices. Then, switch the RCD back on and turn each breaker on one by one. If the RCD trips when you turn on a particular switch, the problem lies in that circuit or a connected device.

Check for moisture or damaged cables

Inspect sockets, connections, and extension cords in damp areas. If you notice a burning smell, sparks, or excessive heat in equipment or wiring, don’t touch them and call a technician.

Don’t bypass it

The RCD is a highly sensitive safety device. Tampering with or bypassing it puts you at risk, which is why it should only be inspected by a certified electrician. Trying to repair it without proper knowledge can leave your home unprotected and increase the risk of accidents.

Replace the RCD if it’s damaged

Like any electrical component, the RCD has a limited lifespan. If it doesn’t react or work properly when pressing the test button, or doesn’t stay on, it needs to be replaced.

Stop the trips: How to prevent your circuit breaker from recurring outages

Test the RCD

Every RCD has a test button, usually marked with the letter ‘T.’ Simply pressing it allows you to verify that the mechanism is working properly. Ideally, you should do this once a month or at regular intervals.

Keep outlets moisture-free

Moisture is one of the electrical system’s main enemies. If you have connections in bathrooms, kitchens, or outdoor areas like terraces, make sure they’re protected with the proper IP-rated outlets. Also, avoid handling electrical devices, sockets, and switches with wet hands.

Check your appliances

Make sure your appliances with motors, heating elements, or electronic components are in good condition, since damage or defects can cause small leaks. If the RCD trips when you turn on an appliance, it likely has a fault. Disconnect it and schedule a technical inspection.

Upgrade your wiring

If you use a lot of electronic devices or smart home systems, conventional RCDs may be too sensitive. There are RCDs that are better protected against small electrical disturbances (type A, AC, or super-immunised).

Super-immunised or selective models are specifically designed to prevent unnecessary trips caused by minor disturbances or current spikes. If you’re unsure which one you need, consult a certified installer for the best option for your home.

Avoid overloading power strips

Try not to plug too many devices into the same power strip. Excessive use of multi-way adapters or power strips can cause overloads. Therefore, it’s best to distribute electrical consumption across different circuits and avoid connecting too many appliances to a single point.

Also, unplug devices you’re not using to reduce the risk of leaks. And if a specific appliance frequently trips the RCD, stop using it until it’s checked by a technician.

Periodic maintenance

Routine maintenance of your electrical installation is essential, as an old installation without scheduled inspections can cause current leakage. It’s recommended that a certified electrician check the condition of cables, sockets, and outlets. If needed, deteriorated or burnt components must be replaced —especially if your home is more than 20 years old.

Prevention and awareness are key

Never ignore frequent RCD trips —they may signal a real current leak. The RCD is an essential ally for home electrical safety.

We recommend installing surge protectors to prevent damage to sensitive equipment such as computers, TVs, or routers. Furthermore, make sure your electrical panel is accessible and clearly labelled. In case of emergency, it’s important to be able to cut the power quickly.

Another way to protect yourself and prevent unexpected RCD trips is to educate household members. Everyone should know how to plug in devices safely, use them responsibly, and avoid mistakes that could compromise the safety of the installation. It’s also crucial that they —especially children and seniors— know exactly what to do if the RCD trips.

With proper maintenance, an adequate installation, and responsible use of electrical appliances, you can minimise interruptions and ensure a safe, efficient environment. This way, you’ll not only reduce unnecessary trips but also extend the lifespan of your appliances and other equipment, keeping your home safe and efficient.

And if you’re ever in doubt or experience recurring issues, it’s always best to contact qualified professionals —like the ones Endesa offers— to safely and reliably diagnose and repair your electrical installation:

FAQs about the RCD

Why your RCD only trips once in a while

This device only triggers when it detects a current leak —an event that, by nature, is rarely constant. That’s why you might experience trips on some days but not on others. Occasional tripping isn't necessarily a cause for alarm, but it should be seen as a signal to inspect your system or check the condition of your appliances.

Is it dangerous when the RCD trips?

Yes. Indeed, it indicates a current leak, which could mean an electrical hazard or contact with water. We recommend checking it immediately.

What happens if I don’t fix it?

You risk fire, electrocution, or damage to your electrical appliances.

What are the most common mistakes in these cases?

Ignoring the problem, failing to identify the affected circuit and resetting it without contacting a specialised technician.

Can home protection be improved?

Yes —by installing super-immunised RCDs and arc-fault detectors, as well as scheduling regular inspections of your installation.

When to call an electrician

We recommend consulting a certified electrician to troubleshoot the root cause of the current leak and ensure your entire system is safe and compliant.