(ch) External lightning protection consists of all of the devices for capturing and discharging the lightning current to the grounding system:
- Capture devices
A mesh is installed on the roofing with a mesh size of 10 m x 20 m. No point of the roof surface may be more than 5 m from the next capture device. Roof structures made of non-conducting material are considered protected if they do not extent beyond the level of the mesh by more than 0.3 m. If they extend further out, they must be equipped with a capture point, which is connected with the mesh. Roof structures made of metal are not connected to the mesh if they
• protrude no more than 0.3 m above the level of the mesh,
• are at least 0.5 m away from a capture device, and
• have no more than a 1 m² enclosed area or are max. 2 m long. - Dischargers
Dischargers are electrically conductive connections between capture devices andfthe ground. The required number of dischargers is given by the circumference of the outer roof edge. Up to max. 20 m, one discharger is sufficient. For more than 20 m, the roof circumference is divided by 20. This yields the number of dischargers. Decimals are generally rounded up. The dischargers should be placed on the corners and junctions of the mesh. - Grounding system
A grounding system must be installed for lightning protection if, for example, no foundation earth electrode is present. The system must be operative without the use of metallic water pipes, ducts or grounded conductors.
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