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Fuse box explained - what are which switches?

From myHOMEBOOK | November 17, 2020, 2:20 p.m.

Anyone who has ever connected a lamp knows the fuse box in their home. But why are some switches not assigned to a circuit? And what do all the switches mean?

“The fuse is out!” Does this sentence bring back memories? Did you run into the basement of your parents' house to see which switch was flipped in a different direction than the others? Then you already know the most important and most fundamental function of the circuit distributor, which everyone probably knows by its slang term - fuse box. It is connected directly to the power grid, from here the cables are drawn through the apartment or house, for example to sockets and lamps.

Why does the fuse box have so many switches?

Behind every switch that is assigned to a room there is a separate electrical circuit. This means that a new line has been laid from the main power line into a certain room. Some rooms even have multiple power circuits, for example when devices with high power consumption have to be connected. This can be the case in the kitchen, where you work with stove, oven, refrigerator and other kitchen appliances and, of course, also need electricity for the light. A second circuit is then created here so that the line is not overloaded.

How many backups do you need?

Each room usually has at least one electrical circuit of its own, which can be switched off individually. Anyone who lives in a house has additional fuses, for example for electricity in the garden. The switches can be used to interrupt individual electrical circuits, for example when working on sockets or lamps. But not all switches have such an obvious function.

In addition: the fuse is constantly blown - what can you do about it?

Structure of a fuse box

The fuse box consists of a sturdy cladding, an easy-to-open cover and mounting rails onto which the various fuse elements can be attached. The elements are then in turn connected to the respective electrical circuit. The fuse box must always be easily accessible.


The fuses - or automatic circuit breakers - are the main element of every distribution box and usually the only important element. Behind every switch there is a circuit that supplies a specific room or specific device with power. This detects overloads in the circuit and switches off automatically. A circuit breaker (LS switch) is usually used, in Germany it is mandatory for all circuits that connect sockets or lighting elements.

FI circuit breaker

Life insurance for people and homes: the FI switch. It reacts to the smallest deviations in the power grid. He recognizes, this is also what the abbreviation stands for, error (F) in the current strength (I). Normally the strength of the current flow is constant and constant. If an irregularity occurs - for example if someone reaches into a socket - the switch instantly recognizes the change and switches off the electrical circuit. It happens in less than a second. In newer households, an FI switch is mandatory, in old buildings it is worth retrofitting if there is no FI switch.

Also interesting: How many devices are allowed to be connected to a multiple socket?

Other elements

In a fuse box there are usually many other elements that are used depending on the situation, such as a fuse or a bell transformer. When installing or moving in, an electrician can explain which elements are intended for what.

Always have work on the fuse box carried out by a professional!

Editor's note:
Working on fuses or installing a fuse box requires the expertise of a professional. Under no circumstances should you try to install new circuits or replace switches yourself. Contact an electrician to do this. According to Paragraph 13 of the Low Voltage Connection Ordinance (NAV), electrical installations belong in the hands of a trained expert, for example an electrician. Otherwise, in the event of damage, the insurance may not pay.

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