LIGHTNING ROD AND DOWN CONDUCTOR INSTALLATION

The lightning conductor principles of installation are given in two main standards: IEC / NF EN 62305-3 & 4 for the protection of structures against lightning and NF C 17-102 for the protection by ESE Lightning conductor on structures and open areas :

• The lightning conductor is installed on the highest point, fitted on a (or several) mast(s) in galvanized steel or stainless steel 2 meters above any other elements.
  • From the lightning conductor, run one or several down conductors in tined copper tape 30*2 mm fixed in three points per meter.
  • Two down conductors:
  → For simple rod: route of the conductor > 35 m
  → For ESE Lightning conductor: • Height of the building > 28 m
  • Height chimneys or churches > 40 m
  • Horizontal route > vertical route
  • If there are several lightning conductors on the structure, they are connected together, but should not be connected if the connection must clear an obstacle (wall, fire break, parapet wall) with a positive or negative level difference in excess of 1.50 m.
  • The copper down conductors are made of tapes, braids, or round with minimum section of 50 mm2.
  • At the bottom of the down conductor there must be installed a control junction and a 2 meters mechanical protective tube.
  • The exterior metal grounds are connected in equipotential configuration to the lightning conductor circuit according to the safety distances of the NF C 17-100 which also advises the distances to maintain between the down conductors.
  • If a discharge counter is required, it is installed above the control junction.
   

For meshed cages, the 4 previous points are valables but in addition with the strike points which will be installed on the roof at maximum every 15 meters and on all the angles of the building.
Vertical section of 40 cm maximum is allowed for crossing of a parapet wall with a slope lower or equal to 45° :
Route of the down conductor:
→ As direct as possible
→ As short as possible
→ Avoiding sudden right-angle bends
→ Avoiding upward sections
• Avoid the contour of a parapet wall. If it is not possible then :
No danger of electric breakdown if d > l / 20
d = length of the loop
l = width of the loop
• A vertical section of 40 cm maximum is allowed for crossing of a parapet wall with a slope lower or equal to 45°.
• You can use certain metallic elements of the structure to act as the down conductor if they correspond to the standards NF C 17-100 and NF C 17-102 standards.
• For the diverting of down conductors, bends formed edgewise should preferably be used.
• When there is a presence of a radio broadcasting receiver antenna, and in compliance to the NFC 90-120 standard, the antenna support mast should be connected through a surge protection device or a spark gap to the down conductors of the installation.
• The safety distance is defined in the NF C 17-102 and NF C 17-100 standards with the formula :
S(m) = n*(ki / km) * l
n: coefficient governed by the number of down conductors interconnected
ki: depends on the level of protection
km: depends on the material between the two extremities of the loop
l: vertical distance between the point where the proximity is taken into account and the earthing system of the mass or equipotential junction.
• In case of churches equipped with 2 down conductors, if a non metallic cross or a statue is situated at the extremity of the nave, this will be equipped with a capture point.
• In case of open areas, the ESE Lightning conductor will be installed on lightning masts, towers, or other existing structures.

checking of the installaTIONS

The checking of the installation depends on the level of protection ( every 2 years for a level I and every 4 years for a level IV).