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In Technical tips

By Steven Roziers

What is earthing and why is this mandatory?

On 30, May 2018 | No Comments | In Technical tips | By Steven Roziers

Before you may start using a new electrical installation, it has to be inspected. The inspector thoroughly checks if everything lives up to the safety prescriptions. You can find these in the Generel Guidelines for Electric Appliances.

One of the conditions laid out in the Guidelines for Electrical Equipment and Appliances is the earthing. But what exactly is this earthing and what is its use? We will provide you with all the answers in this article.

What is earthing?

The earthing is a metal conductor that connects all the electrical appliances and that taps off leakage current to the earth around the house. It forms an essential part of every installation, since this earthing or grounding prevents electrocutions from happening. When an erroneous isolation occurs, a differentiation switch will automatically turn off the power.

For instance: While you were moving your washing machine, the cable got severely damaged. The power wires are visible and stand in direct contact with the metal casing of the appliance. If you would touch the washing machine, you would be electrocuted. Unless you have a grounding that is. This earthing will send the electric current down to the earth and prevents tragic accidents in this way.


You can recognize the grounding conductor by its yellow-green isolation.

Earthing for new constructions

For a new construction with foundations of at least 60 cm deep, an earth loop is used. This is a copper conductor with a 35mm² diameter on the bottom of the foundation slot. This wire cannot touch the foundation walls under any circumstances and therefore it has to be covered in ground. The ends stay free and open. They are usually joined at the height of the grounding switch.

Earthing for already existing buildings

Some older buildings do not have earthing yet or they have a malfunctioning grounding. It is not possible to place a grounding loop here. Luckily there is another solution: You can provide one or several ground rods (keep them at least at 3 meters from each other). These metal pins are hammered 80 cm into the ground and connected to the electrical installation using earth conductors. The earth conductor connects the earth electrode with the grounding breaker and the main earthing clamp. The section of this conductor is minimum 16 mm², provided it has been equipped with a yellow-green isolator, or 25 mm², if it is not isolated.

Other components

Apart from the grounding loop or earth electrodes, we still need an earthing conductor that connects everything to the main grounding rail. This earthing conductor has a diameter of at least 16 mm². Also make sure to provide an earthing disruptor to test the resistance. The resistance may not exceed 30 Ohm.


Example of a grounding disruptor. Photo source

For which elements do we need earthing?

There are different elements in your house that need a grounding, starting with sockets and light points  You can recognize the protective conductor by its yellow-green isolation. It should have the same diameter as the phase conductor.

Apart from that, certain metal components get a protection against dangerous voltage. Equipotential connections are used for this purpose. We can mainly summarize them in two kinds:

  1. The major equipotential connections: for major lines of gas, water and central heating. Yellow-green wires of at least 6 mm² wide.
  2. Additional equipotential connections: for the metal structures of a bathroom (bath tub, drain etc.). This connection, isolated with yellow-green wire, has a diameter of at least 2,5 mm², if it is placed in a tube. If not, a diameter is 4 mm² is mandatory.

In our web shop you can get clamps to attach the grounding wire on the lines and other elements.

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