Lightning Mast Height

[garciasr77]

How high above other metal structures (antennas or other rods) does the lightning rod/Air Terminal have to be? NFPA 780 says that "air terminal height shall not be less than 10 in. above the object or area it is to protect." Does this include antennas or other metal parts?

 

[ghostbuster]

Our general rule of thumb is for the protected element to be 45 degrees or greater below the air terminal.(zone of protection)

 

[brian john]

Not saying ghost is right or wrong, but rule of thumbs can get your hand slammed in the door.

NFPA 780 Standard for the Installation of Lightning Protection Systems, 2000 Edition



http://www.nfpa.org/catalog/product.asp?category_name=&pid=78000&cookie_test=1

 

[bphgravity]

Any type of irregular roof protrusions will likely require a strike termination device. In the case of an antenna, it is possible the antenna structure itself can serve as the strike termination device. (see 4.17 - NFPA 780) In any case, the antenna needs to be bonded to the LPS. Other metal structures such as masts and flagpoles are also treated as strike termination points and should comply with 5.2 of the NFPA 780.