LIGHTNING PROTECTION DOWNCONDUCTORS IN CONCRETE

[ROMM]

Hello All,
Anyone know of specific requirments for installation of lightning protection downconductors(viz 120sqmm bare copper conductor) in concrete on their way to the buried earthgrid.

Any feedback greatly appreciated.

 

[jghrist]

Per NFPA 780-2000, Standard for the Installation of Lightning Protection Systems:

3.19.13 - "Down conductors coursed on or in reinforced concrete columns...shall be connected to the reinforcing steel...at their upper and lower extremities. In the case of long vertical members, and additional connection shall be made at intervals not exceeding 200 ft (60 m)."

The concern is to avoid side flashes through concrete to reinforcing steel that provides a parallel path for the lightning. Bonding the rebar to the down conductor prevents the lightning current from flowing through the concrete.