A ground fault circuit interrupter is a safety device that protects you from dangerous electrical shocks by disconnecting the power immediately when it detects a fault. It measures the current balance between phase and neutral, and reacts within milliseconds if current leaks to ground. The ground fault circuit interrupter is required by law in Norwegian homes and serves as your most important protection against electrical accidents in the home.
What is a ground fault circuit interrupter and why is it important?
A ground fault circuit interrupter is a vital safety device that protects you from electrical shock by monitoring the current flowing into and out of your electrical system. If it detects that current is leaking to ground, for example through a person touching a faulty appliance, it will disconnect the power in less than 0.04 seconds.
The RCD is required by law in all Norwegian homes, and it is intended to protect circuits in wet rooms, outdoor sockets and other areas where the risk of electric shock is high. You will usually find it in the fuse box, often as a separate unit with a test button marked "T".
Without a ground fault circuit interrupter, even small electrical faults can become life-threatening. It protects you in situations where regular fuses won't help, because it reacts to current leakage and not just overload. This makes it your most important insurance against electrical accidents in your home.
How does a ground fault circuit interrupter work in practice?
The RCD continuously measures the current flowing in through the phase and out through the neutral. In a normal electrical system, these two should be exactly the same. When you turn on a light or appliance, the current flows in through the phase, powers the appliance, and returns through the neutral.
If current starts to leak to earth, for example through a damaged cable or a faulty appliance, the current that returns will be less than the current that went out. The RCD detects this imbalance in current and disconnects the power supply in 20-40 milliseconds.
This is what distinguishes the RCD from regular fuses. A RCD protects against overload and short circuit by measuring total current, while the RCD protects against current leakage. You need both types of protection in a modern electrical installation.
The RCD usually responds when the current leakage exceeds 30 milliamperes. This is fast enough to prevent serious injury, since dangerous current through the body occurs at higher levels over longer periods of time.
Why does the ground fault circuit interrupter trip and what should you do?
The earth leakage circuit breaker trips when it detects a current leak, and this can have several causes. The most common are damp electrical appliances, defective products with worn cables, or actual faults in the electrical system. If the washing machine is in a damp basement or you use electrical tools outdoors in the rain, moisture can cause current leaks.
When the RCD trips, you should do the following:
- Disconnect all appliances on the circuit in question.
- Check if any devices are damp or have visible damage.
- Press the test button (T) on the RCD to check that it is working.
- Turn the ground fault circuit interrupter back on when the appliances are disconnected.
- Connect one device at a time to determine which one is causing the problem
If the RCD trips immediately after you plug it back in, even without any appliances connected, there is probably a fault in the electrical system . This can be dangerous and you should contact an electrician immediately.
It is safe to reset the RCD if you have identified and removed the faulty appliance. However, if you are unsure of the cause, or if it trips repeatedly for no apparent reason, you should have a professional inspect the system.
What is the difference between a ground fault circuit interrupter and a circuit breaker?
Ground fault circuit interrupters and circuit breakers have completely different functions in the electrical system. A circuit breaker protects against overload and short circuits by measuring how much current flows through the circuit. If you connect too many devices at the same time, or if a short circuit occurs, the circuit breaker trips to prevent overheating and fire.
The earth leakage circuit breaker, on the other hand, protects against current leakage that can be dangerous to people. It does not measure the total current, but the difference between the current flowing in and out. Even a small current leakage of 30 milliamperes causes the earth leakage circuit breaker to trip, while a circuit breaker does not react until the current reaches many amperes.
The two devices complement each other in a modern electrical system. The circuit breaker protects cables and equipment from damage, while the earth leakage circuit breaker protects you from electric shock. When the circuit breaker trips, it is usually because you have connected too much or because an appliance has a short circuit. When the earth leakage circuit breaker trips, it is because current is leaking to ground.
You can tell the difference in the fuse box. Circuit breakers are usually smaller switches marked with amps (10A, 16A, 20A), while the RCD is larger and has a test button marked with a "T".
How we help with ground fault circuit interrupter problems
When your RCD trips and you can't find the cause yourself, we can help you quickly and safely. Our qualified electricians are experienced with all types of electrical problems related to RCDs and safety systems.
We offer:
- 24/7 customer service that answers your call immediately, every day of the year
- Fast response time with an electrician on site within one hour for urgent assignments
- Troubleshooting electrical systems to find the cause of the RCD tripping
- Replacement of defective earth leakage circuit breakers and upgrading of fuse boxes
- Scheduled same-day or next business day assignments for non-urgent issues
Our network of local electricians covers the whole of Norway, and we connect you with the right professional who knows your region's building stock and electrical standards. Many problems can be solved over the phone with advice from our experienced customer service team, and the call is always free.
Call 401 24 700 for emergencies or visit 24center.no for scheduled visits. We ensure that you get professional help when you need it most. Read more about our services and how we can help you with all types of electrical challenges.
Vanlige spørsmål
How often should I test my RCD?
You should test your RCD at least once every three months by pressing the test button marked “T”. If the breaker does not trip when you press the test button, it is not working properly and must be replaced immediately by an electrician. Regular testing ensures that your RCD will protect you when you really need it.
Can I replace the ground fault circuit interrupter myself, or do I need to use an electrician?
In Norway, all work in the fuse box must be carried out by a licensed electrician. This is required by law for safety reasons, as incorrect installation can be life-threatening and lead to fire or electric shock. Although it may seem like a simple job, it requires professional knowledge of electrical systems and proper wiring to ensure that the RCD works correctly.
What should I do if the ground fault circuit interrupter trips in the middle of the night?
If the RCD trips at night, it is safe to reconnect it after you have disconnected all appliances on the circuit. Use a flashlight to safely navigate to the fuse box. If it trips again immediately with no appliances connected, leave it disconnected and call an electrician on duty. This may indicate a serious fault in the system that requires immediate attention.
Can an old electrical system cause the ground fault circuit interrupter to trip frequently?
Yes, older electrical systems with worn insulation on cables can cause frequent trips. Over time, the insulation on cables can break down due to moisture, heat and age, creating small current leaks. If the RCD trips frequently without you finding any faulty appliances, you should have an electrician inspect the system and assess whether it is time to upgrade or replace old cables.
Are there different types of RCDs, and which one do I need?
Yes, the most common types are AC type (standard for most homes), A type (for appliances with electronics such as heat pumps and electric car chargers), and B type (for special industrial applications). For modern homes with heat pumps or electric car chargers, A type RCDs are often recommended. An electrician can assess your installation and recommend the right type based on the appliances you have installed.
Why does the ground fault circuit interrupter trip during a thunderstorm?
Thunderstorms can cause voltage spikes and electromagnetic disturbances in the electrical system, which in some cases can trip the RCD. Nearby lightning strikes can also cause temporary power leaks. This is usually not dangerous, and you can turn the RCD back on after the thunderstorm has passed. For additional protection, consider installing a surge protector.
Does insurance cover damages if I don't have a ground fault circuit interrupter?
Since a ground fault circuit interrupter is required by law in Norwegian homes, a missing or defective ground fault circuit interrupter can negatively affect insurance coverage in the event of electrical damage or accidents. Insurance companies may reject claims if it is found that the home does not meet applicable electrical safety requirements. Therefore, always ensure that the ground fault circuit interrupter is installed, functioning correctly, and tested regularly.
