lightning protection

[AYahya]

What is the recommended ground resistance for a lightning protection system?

i have a system consisting of 3 lightning rods connected to network of 4 earth rods and the earth resistance measured is 1.2 ohm. where is that from the standard?

 

[rbulsara]

Look up IEEE Green book on grounding. Not sure NFPA 780 specifies anything, but worth looking into.

I would think anything less than 5 ohms is good. Anything less then 1 ohm is ideal. Lower the merrier.

More importantly make sure your LP grounding electrode system is connected to building service grounding electrode system. It is Code requirement and recoemmended practice.

 

[opmgr1]

The IEEE green book recommends 1-5 ohms range.