Electrical installation for wallboxes: Cable cross-sections

Installer power line

A wallbox cannot be connected to every cable. Cross-sections and insulation: We explain how to choose the right one.

If you want to install a charging station for your electric car at home, there are many things to consider: Charging power, charging cable, plug type. But many people forget that the charging process doesn't just start with the wallbox. The supply cable to the home charging station is also essential to ensure that charging at home not only works well, but is also safe. The decisive factor here is the cross-section of the cable. In the best case, the existing connection can be used without any problems; you may just have to be careful when choosing the right charging station. In the worst case, however, a new cable may have to be laid. The supply cable should therefore always be checked before installation! This also helps to avoid cost traps. In this article, you will find out what you need to know about the supply cable to the wallbox.

Power cable: these are the basics

The function of a power cable is to conduct electricity from A to B. It does this via wires, the so-called cores. The cores are made of a conductive material, usually copper, but aluminum or silver are also used. Each individual core and the core assembly as a whole are in turn surrounded by one or more insulating layers. A final sheath protects the cables and/or provides electromagnetic shielding.

Not every cable is suitable for every application. Especially when it comes to higher currents, factors such as the ambient temperature and the cross-sectional area of the conductors play an important role. They determine the current carrying capacity of the cable. If the cable is too thin for a certain amperage, it may not be able to be used for charging with the desired charging capacity. The environment is also relevant for selecting the right cable, for example whether it is laid in the wall or outdoors.

Adapt the supply cable to the charging power

The minimum diameter of the supply cable can be calculated using the ambient temperature, the cable length and the required charging power. Approximate guide values can be found in the table below. For intermediate values, please always select the next larger size. It may also make sense to opt for the next largest cross-section in order to reduce power losses and to be able to upgrade later. At this point, it should be noted that a longer cable can also be worthwhile. Although a cable that is too long leads to power losses, it is still possible to shorten the cable later - cutting it to length is difficult, however. The electrician can then shorten the cable to a suitable length when installing the wallbox.

The cross-section of a particular cable can usually be found in the product name. This is made up of the following components:

Cable type: NYM-J

Number of cores: 3x

Cable cross-section: 1.5 mm²

The cable type NYM-J 3x1.5mm² mentioned in the example is most commonly used in German households.

You can find out whether your supply cable is sufficient with our video installation check. We will also be happy to help you choose a suitable wallbox and the right electricity tariff.

Conclusion

Before deciding on a wallbox and therefore a specific charging power, the supply cable should be checked. For cost reasons, it may make sense to choose a lower charging power if laying a new cable is too expensive or if very high demands are placed on a cable. In this case, a lower charging power can save money both on the supply cable and on the wallbox itself. The disadvantage, however, is the longer charging time for the electric car. But whatever you decide: It can't hurt to know your options in advance.

Topics: Installation Wallbox

Electrical installation for wallboxes: Cable cross-sections

Power cable: these are the basics

Adapt the supply cable to the charging power

Conclusion

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