Home generalFI switch / fuse constantly flies out - solutions

FI switch / fuse constantly flies out - solutions

  • Difference RCD and fuse
  • The fuse trips: Cause
    • shorts
    • overload
  • Fuse triggers: solutions
    • Traces of smoke and odor
    • Damage to the line
  • The FI switch triggers: Cause and remedy
  • No experiments

If the fuse or the FI-switch triggers in an apartment, then the circuit is interrupted in a certain area or in the whole apartment. You are suddenly in the dark. Even if you have found the fuse box quickly, the problem with switching on the fuse or the FI switch is not resolved. A detailed analysis of the damage is necessary in any case.

Difference RCD and fuse

The FI switch usually shuts the whole apartment dead. It is clearly visible in the fuse box, as it is wider and mostly provided with a red mark . The function of the residual current circuit breaker is vital: it detects when the housing of an electrical appliance is energized and switches off before anyone touches it.

A fuse is usually much narrower and has a black switch. In most households, the fuse is labeled with what it is responsible for. Mostly these are the individual rooms. In the kitchen, however, there are usually several fused circuits built in.


From a technical point of view, RCD and fuse are the same in function. However, the residual current circuit breaker is intended for the protection of persons or animals, while the normal fuse should only protect the line.

The fuse trips: Cause

If a single fuse trips, then there is either a short circuit or an overload in the circuit. A short circuit can occur in the line itself, in the connection points such as switches and sockets or in the connected devices.


A typical case of a short circuit in a pipe occurs when it is accidentally drilled when setting a dowel. Otherwise, the line may become embrittled due to aging, be nibbled by an animal or spotted by a thermal overload. However, the damage in the line is very rare.


The light switches and sockets can be contaminated by haze, causing a short circuit. Especially in the kitchen, this happens relatively quickly if no cooker hood is used. The haze forms a lubricating film, which connects the separate poles in light switch or socket together. However, a short circuit in a socket or a light switch is usually accompanied by a clearly visible and smell smearing. Here only the replacement of the switch and the installation of an extractor fan helps. In workshops metal dust can also lead to short circuits of this kind. The installation of flap closable sockets can be an effective protection here.

A short circuit in the device occurs if it has an internal defect. This can have many causes. In the interior of electrical devices, the cables usually break loose when they fall, fall over or are otherwise mechanically damaged. Overaging, overloading or other improper handling may also cause short circuits. And of course, electrical appliances are also sensitive to haze or moisture.


Another typical case of triggering the fuse switch is overload. This occurs when too many high power devices are operated simultaneously in a single circuit. For this reason, the washing machine, refrigerator, clothes dryer, dishwasher and stove are usually connected to separate safety switches.

Overload may also occur if a too long power cord is plugged into a power outlet. With the length of the power line, the resistance in her increases, whereupon she reacts with a warm-up. This is registered by the circuit breaker and it shuts off the line before it can blow. Therefore, the triggering of a fuse switch occasionally does not occur immediately after the connection of an extension lead. The line takes some time to reach the critical temperature at which the circuit breaker triggers.

Extension cable too long

The cause of an overload is usually too low a line cross section or too weak a fuse. Both can be solved by a professional electrician.

Fuse triggers: solutions

The advantage of the triggered circuit breaker is that you can limit the defective circuit very well. Now all you have to do is ask yourself what has been done last: if the circuit breaker trips immediately after turning on a device, the cause will be. Now the only question is whether the fault was due to the device or the fuse. Some security circles are also just too weakly secured. To do this, simply plug the device into the socket of another circuit and turn it on. If it runs smoothly, the previous circuit is probably underfused.

Washing machine

This error occurs, for example, relatively often in radiant heaters, air conditioners or powerful vacuum cleaners . But triggers any safety switch, regardless of which circuit you connect the device, then it is likely to be defective. As a layman one should now undertake no repair attempt on the device, but leave it to a professional service provider. Often these defects are due to a short circuit in the cable, which can be easily exchanged for a few euros.

Traces of smoke and odor

If the error occurs without a device connected, it must be further limited. If traces of smoke and a distinctly smelly odor are detected at one of the connection points of the affected circuit, the fault has usually been found. Replacing a light switch or socket is basically not difficult, but should be done as conscientiously as possible. With the slightest doubt, booking a specialist is always the better advice.

Damage to the line

A clear case for the professional electrician is when the fault occurs in the line itself. No repair attempts should be made here, even if - for example by drilling - you know exactly where the error occurred. A faulty cable in the wall can completely power them up. Then, in the worst case, the slightest touch is enough to get a 220 V electric shock. An error of this kind, for example, often occurs when mounting a new handrail for the shower head. Especially here an electrical damage is particularly critical, which often ends fatally.

The FI switch triggers: Cause and remedy

The FI switch is a special circuit breaker designed to protect the lives of people and possibly even animals. Its tripping behavior is similar to that of the circuit breakers. He usually turns off the whole apartment. To restore the power supply, it is systematic.

Switch off fuses
  1. Turn off all fuses
  2. Disconnect all electrical equipment
  3. Turn off the light switch.
  4. Turn on the RCCB again
  5. Turn on one circuit breaker after the other

If the RCD now triggers, the line is damaged on the affected circuit. Only a professional electrician can help here.

  1. Turn on the light in the whole apartment again
    If the residual current circuit breaker now trips, one of the light switches is damaged. This can now be examined more thoroughly, replaced as a precaution or repaired by an electrician.
  1. Plug in the electrical appliances
    If the residual current circuit breaker triggers, the faulty device has been identified. This will be removed, disposed of or equipped with a warning sign until inspection by an electrician.

With this method, one can safely and reliably identify a source of error in the power supply.

No experiments

It is absolutely forbidden and dangerous for a person to bypass a safety switch or a residual current circuit breaker in any way or to block it from tripping. All that is achieved is a cable fire in the device, the connection points or in the power line itself. This can lead to a fire of the house.

Tips for quick readers

  • learn the flashlight function on the smartphone
  • Know in the dark where to find a flashlight
  • perform systematic troubleshooting
  • no experiments
  • Safety note
  • Dispose of defective devices or have them repaired professionally
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