NFPA 780 Lightning Protection

Question 1

How far apart can you space air terminals on a pitched roof?

Answer 1

A: 20-ft or 25-ft maximum spacing along the top of the pitch.

B: Within 2-ft of the end of the ridge.

Question 2

How far apart can you space air terminals on a flat roof?

Answer 2

A: 50-ft (15-m) maximum spacing between air terminals

B: 150-ft (45-m) maximum length of cross run conductor permitted without a connection from the cross run conductor to the main perimeter or down conductor

C: 20-ft (6-m) or 25-ft (7.6-m) maximum spacings between air terminals along edge

Question 3

What is the rolling sphere method?

Answer 3

The method to determine the coverage of a lightening protection device by rolling a 150ft radius sphere from that inflection point to find the area it does not protect.