Bonding Equipment Ground Conductor to Lightning Air Terminal

[Electriman]

Dear Friends,

I have recently come to a problem and that is whether or not we are allowed to connect lightning air terminal to equipment ground conductor. The other option of course is to install a separate ground conductor for each air terminal. Please support your responses with Code clause.

Thanks,

 

[augie47]

Assuming we are referencing communications circuits (Art 800) or Broadband communications (Arty 830) you can reference ***.100 in those sections. It appears the preference is the ISBT with the building electrode system as the second choice.

 

[Electriman]

Assuming we are referencing communications circuits (Art 800) or Broadband communications (Arty 830) you can reference ***.100 in those sections. It appears the preference is the ISBT with the building electrode system as the second choice.

Thanks Augie,

My application is actually outdoor lighting. Does it make a difference if it is lighting or communication?

 

[augie47]

Sorry, I misunderstood the question.
I'll defer to someone more knowledgeable, but on first read of Art 280,285 and 250 Part III, I'd say you need to terminate on the grounding electrode system but we will see.

 

[don_resqcapt19]

You need to look at NFPA 780, the Lightning Protection Code. I don't think you are permitted to connect an air terminal to the electrical grounding system, however the electrical grounding system is required to be bonded to the lightning protection grounding system.

 

[winnie]

My (non-professional in the field of lightning protection) understanding is that you are _required_ to all of your grounding electrodes together, which means that your lightning protection system grounding electrodes will be bonded to your electrical system grounding electrodes, and that there will be a metallic path from your lightning air electrode to your EGC, so in a round-about way they will be connected together.

However I don't believe that an electrical system EGC will in general be suitable for use as a lightning down conductor. The requirements for EGCs are in general different from those for lightning conductors, covered by separate codes.

-Jon

 

[Electriman]

My (non-professional in the field of lightning protection) understanding is that you are _required_ to all of your grounding electrodes together, which means that your lightning protection system grounding electrodes will be bonded to your electrical system grounding electrodes, and that there will be a metallic path from your lightning air electrode to your EGC, so in a round-about way they will be connected together.

However I don't believe that an electrical system EGC will in general be suitable for use as a lightning down conductor. The requirements for EGCs are in general different from those for lightning conductors, covered by separate codes.

-Jon

That is what I think so. But I am just confused where I see power transformers use the same EGC for MOV lightning protection and transformer enclosure.

 

[Strathead]

That is what I think so. But I am just confused where I see power transformers use the same EGC for MOV lightning protection and transformer enclosure.

Also not a lightning expert, but you definitely learn a lot from osmosis in Florida. It is a lightning protection system. As such the air terminals are attached to the down conductors on a building. I am assuming you are referring to equipment on a roof. This equipment is either in the zone of protection or it requires an air terminal. I believe there are times that it requires the down conductor bonded to it. Even more odd, you have to look at lightning sort of like water. You can't just route the conductors willy nilly. They must flow downhill. they can go up, say over a parapet, but there are restrictions on the angle. Also, one last thing the lightning conductor is a listed wire Class one or class two it is not a bare grounding wire, or a green insulated conductor. So, no, you can't bond it to the EGC.