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DEHN FAQ
DEHN protects buildings

FAQ – Earthing

1. According to DIN 18014, is a ring earth electrode or a foundation earth electrode required?

Foundation earth electrode:
For all new buildings since a foundation earth electrode is required by DIN 18015, the latest technical connection conditions of the utility and the future connection rules AR4100.

Ring earth electrode:
When the earth electrode in the foundation (foundation earth electrode) does not have sufficient contact with earth. This is usually the case with building waterproofing, i.e. foundations with increased earth contact resistance, e.g. a white tank, perimeter insulation, foam glass gravel


2. Why do the connection points on the ring earth electrode have to be wrapped with an insulating tape if V4A material is used?
Connection points in the soil are generally a weak point - with regard to corrosion and when high-quality material such as V4A is used. This is why the standard (DIN 18014) requires that these points should be wrapped with insulating tape.


3. Which mesh size has to be used for ring and foundation earth electrodes?
The maximum mesh size for both foundation and ring earth electrodes is 20 m x 20 m.
However, in combination with a lightning protection system, the mesh size for ring earth electrodes must be 10 m x 10 m. It is advisable to use a mesh size of 10 x 10 m for ring earth electrodes to ensure that a lightning protection system can be retrofitted.


4. Is a ring earth electrode always required in combination with a lightning protection system?
No. According to DIN 18014, the earth-termination system for a lightning protection system can either be a ring earth electrode or a foundation earth electrode. The lightning protection system must then be erected according to Part 3 of the EN 62305 lightning protection standard.


5. What are the distances from the ring earth electrode and foundation earth electrode to the edge of the building?
A gap of at least 1 metre is required between the ring earth electrode and the building and the ring earth electrode should be buried at a depth of at least 0.8 m. The foundation earth electrode should be installed as a closed ring in the floor slab at the outer edge of the foundations (covered by at least 5 cm of concrete).


6. What about buildings with individual foundations?
Individual foundations require an earth electrode with a length of at least 2.5 m. The individual foundations must be interconnected using corrosion-resistant earthing materials V4A - preferably in direct contact with earth. If waterproof concrete is used in the individual foundations, a ring earth electrode must be installed.

 

7. Is it always necessary to mount earth rods?
No, earth rods are not required for the standard configuration of foundation or ring earth electrodes. Earth rods should be used as an alternative if it is not possible to install an earth-termination system which complies with DIN 18014.
In this case, earth rods with a length of at least 3 m can be installed around the building as an additional measure to the ring earth electrode. They are preferably installed at the corners of the building. The distance between the earth rods may not exceed 20 m if there is no lightning protection system and 10 m with if there is a lightning protection system. The earth rods must be connected to the ring earth electrode.


8. Why is a functional bonding conductor and a ring earth electrode required?
According to DIN 18014, a functional bonding conductor is required in the concrete foundation in addition to a ring earth electrode since the internal equipotential bonding of the building structure (reinforcements, metal structures, etc.) is established here. The functional bonding conductor should be connected to the reinforcement every 2 m and to the ring earth electrode every 20 m (if a lightning protection system is required, every 10 m).


9. The customer has a mixture, e.g. white tank + individual foundations + floor slab (for example, a warehouse: partly concrete floor slab, partly paved).
How can one comply with the standard here?

As a general rule, the design chosen here is based on waterproof concrete. This means that a ring earth electrode must be installed under the floor slab and also under the white tank. This is connected to the functional bonding conductor of the floor slab and that of the white tank.

10. Semi-detached/terraced house with a "white tank" instead of a strip foundation. What does the earthing look like here?

DIN 18014 describes earth-termination systems for foundations with increased earth contact resistance. In this case, a ring earth electrode with functional bonding conductor in the foundation and the relevant connections are required (see Lightning Protection Guide, page 132). In practice, a ring earth electrode with cross connections around the semi-detached houses has proven effective since the foundation slab is usually cast in one piece. The ring earth electrode should be connected to the functional equipotential bonding at the intersections.

 

A - Connection to the external lightning protection
B - Connection to the MEB
C - Functional equipotential bonding
D - Ring earth electrode
E - Connection of the ring earth electrode with the functional equipotential bonding

11. How often does the ring earth electrode have to be connected to the functional equipotential bonding. How often does a terminal lug need to be led to the surface?
If there is no lightning protection system a connection between the functional equipotential bonding and the ring conductor is required every 20 m (depending on the circumference of the building). If a lightning protection system exists, a connection is made with every down conductor. In our experience, the most favourable design comprises the connection of the functional equipotential bonding with the ring earth electrode and a terminal lug to the surface every 10 m. This makes retrofitting a lightning protection system (up to class of LPS II) a simple matter.

 

12. Waterproof concrete (white tank), what kind of wall bushings are required?
Pressure-tight earthing wall bushings, e.g. DEHN Part No. 478530, tested with an air-pressure of 5 bar in compliance with DIN EN 62561-5. The pressure-tight wall bushing should lead into the service entrance room, to enable simple connection of the installation level.

 

13. Can the ring earth electrode be made of V2A?
No! The standard insists on the use of corrosion-resistant material, e.g. V4A, material number 1.4571 or, alternatively, copper wire for laying in the ground.

 

14. Why connect the ring earth electrode and the functional bonding conductor?
If there is a direct lightning strike nearby, there may be dangerous flashover, step voltages and electromagnetic interference. For this reason, the two systems need to be connected to one another. The reinforcements should be connected to the functional bonding conductor at least every 2 m.

 

15. Are the terminal lugs for external lightning protection systems also made of V4A?
As a basic rule, it is advisable for the terminal lugs in the external lightning protection system to be made of V4A. However, according to DIN EN 62305-3, it is also possible to use other materials like, for example, galvanised material with additional corrosion protection (in the transition are between the soil and a

 

16. From what depth does the soaked, frost-free area start for the ring earth electrode?
Earth electrodes should be laid at a depth of at least 0.8 m to guarantee the necessary soaking and, in winter, the corresponding frost depth.

 

17. How should functional equipotential bonding be established with a fibre concrete slab? 
Fibre concrete is often used for the foundation slabs of industrial buildings. A mesh size of 10 x 10 m should be maintained for the ring earth electrode which is, in this case, in the soil below the fibre concrete floor slab or below the blinding layer. If extensive data and automation technology is employed in the building, the mesh size should be reduced to 5 m x 5 m.

 

18. How should a building with individual foundations, partial basement and foundations with a wooden construction be equipped according to DIN 18014?
Please refer to question no. 9

 

19. From which quality is concrete classified as waterproof?
Although waterproof concrete soaks up water, the water does not penetrate all the way through the concrete even after longer periods of time. This means that there is no damp on the inside of the wall. According to DIN EN 206-1/DIN 1045-2 a water penetration depth of 50 mm may not be exceeded for waterproof concrete. This is usually achieved for waterproof concrete at a minimum compression strength class of C25/30. At the same time, the water/cement ratio must be less than 0.6 and the minimum cement content greater than 280 kg/m³.

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