Lightning Protection - Ground rod Bonding

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anbm

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TX
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Designer
For the lightning protection - down lead conductor from roof will goes down and hit ground rod at ground. Is there a code requirement to bond all ground rods together as a loop? I know the air terminals on roof are bonded together but did not see samething happended with the rods at ground level...
 
The ground terminals (i.e., ground rods attached to the down leads from the air terminals) must be bonded to the buildings grounding electrode system. You don't have to do that with a ring. But it is one convenient way to do it. Reference 250.106.
 
They did bond to building grounding system at one of the rods location but did not bond the rods together as a ring...I guess this may not requires. Thanks!
 
I suggest reading 250.106 again. As I read it, all of the ground terminals have to be bonded to the building's system. If that is not done by bonding each to a ring, and bonding that ring to the building's system, then you must bond each ground terminal one by one, or come up with some other way to meet the requirement.
 
But they have the ring on the rood bond all air terminal and downlead conductors, will it serve the same purpose as the ring at ground?
 
Are you required to meet any lightning protection standards such as NFPA 780, UL 96A or LPI 175?

NFPA 780 and LPI 175 require a ground loop for structures over 60' (18m)
UL 96A does not
 
anbm said:
But they have the ring on the rood bond all air terminal and downlead conductors, will it serve the same purpose as the ring at ground?
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No it is not the same. Lightning tends to head toward planet Earth. You need to bond everything at ground level, to make sure it spreads out evenly (or so I would suppose - I really don't know the physics here). It is not going to head up to the roof, get equalized by that ring, and head back downwards again. In any event, the rule says to bond each of the ground terminals to the building's GES.
 
anbm said:
But they have the ring on the rood bond all air terminal and downlead conductors, will it serve the same purpose as the ring at ground?
Click to expand...
Not according to the NEC; it must be each and every electrode. Having them bonded only by wires atop the building could possibly increase damage from a strike.
 
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