For Safety
The RCD
The RCD is a personal protection switch that serves your own safety.
By default, it should be installed as a 40A, 30mA version.
40A is the max current that may flow through the RCD and 30mA is the max fault current at which it must shut off.
An RCD >30mA is not permitted.
One RCD for the entire house is not sufficient, and don't let your electrician tell you otherwise.
A sensible division would be for example:
1 RCD for the sockets
1 RCD for the lighting
1 RCD for the building technology
1 RCD for refrigeration units
1 RCD for the outdoor area including garage/carport
Why all the effort?
If you only have one RCD and a fault occurs, you will be in the dark on your entire property. That is very annoying.
By separating sockets and lighting, at least some light will still work somewhere.
The outdoor area should always be separately protected by an RCD as well, since moisture can cause faults.
RCDs for building technology and refrigeration units are not strictly necessary,
but for example for your frozen goods during summer vacation, it offers a significant advantage if the sockets in the living room fail; the same applies in winter for the heating.
For permanently connected devices (i.e., not via a socket), no RCD is required.
The Fuses
The fuses serve to protect the connected cables so they do not overload and eventually start to burn. They are not sufficient as personal protection (hence the RCD).
In private use, so-called circuit breakers with B-characteristic are used. The B stands for the tripping behavior. In this case 5xIn.
Example 1:
A 16A breaker is installed, a short circuit occurs in the line and a total current of 5x16A = 80A flows, so the breaker trips immediately.
Example 2:
You drilled into the line but only scratched it, causing leakage currents between L and N. The current is still below 5x16A, so the fuse will not trip immediately. However, it will heat up and switch off after a certain time.
This time is specified by the "B" and can be read from diagrams. This time is also the reason why a circuit breaker is not approved as personal protection.
Fuse configuration
The fuses should be at least adapted to the cable cross-section behind them, but better adapted to the application.
For example, I use 16A breakers for the sockets and 6A or 10A breakers for the indoor lighting.
The reason for this diversification is the already mentioned tripping time.
Max 10 sockets per 16A fuse. This is related to the diversity factor.
I learned that on average 300W is drawn per socket. A 16A breaker can handle 3000W, hence 10 sockets.
Each room is protected by a single fuse. A fuse costs around €1.00 wholesale, so don’t let yourself be sold a much higher price, but keep in mind that then each room also gets a separate supply line.
The same applies to lighting. One fuse per room, so usually you don’t have to worry much about the number of fuses. One should be enough unless you plan to install 1000W spotlights.
Large appliances such as washing machines, dryers, refrigerators, dishwashers, ovens, cooktops, fully automatic coffee machines, etc. get their own fuse.
Especially devices with more than 2kW power. For powers from 3kW (instantaneous water heaters), a 16A breaker is no longer sufficient, and the supply line must also be dimensioned larger.
As you can see, quite a lot adds up; accordingly, you should plan your house connection box a bit larger from the start.
An additional empty meter slot can also be advantageous (retrofit heat pump or photovoltaic).