Residual current circuit breaker: the function simply explained

The function of a residual current circuit breaker is to protect people from an electric shock. An FI switch also serves as fire protection. In this article we explain how the circuit breaker works.

Function of the RCCB

The circuit breaker should only be installed by a professional. Electronics pose numerous dangers.

• The current in the lines connected to the RCCB magnetises a so-called summation current transformer in the core of the circuit breaker.
• The flowing current demagnetizes it again. As a result, there should be no magnetic field inside the RCCB.
• However, if less current flows away, for example because it has been discharged into the earth, a remainder of the magnetic field remains and the FI switch trips. This is the case, for example, if you come into contact with electricity.
• So if there is a difference between the incoming and outgoing current in the circuit breaker, this immediately interrupts the current flow.
• For this reason, the RCCB is officially called residual current circuit breaker.
• FI switches switch off the current depending on the model at different amperages. Residual current circuit breakers are installed in residential buildings, which switch off the power within a few milliseconds if there is a difference of 30 milliamps.

In our next post we will explain how the electricity gets into the socket.