Questions regarding lightning protection

[kingbambina]

Hi,
I have two questions regarding lightning protection arrestors and down conductors:

1. We have a gasoline loading bays and there is a grounding busbar for its instrumentation and lighting that's connected to the grounding grid. The canopies of these have lightning arrestors installed, and the down conductors are connected to the bay's existing busbar. Is this the in vialoations of NEC 250.60 or the NFPA 780?

2. Some of these arrestors have a relatively high resistance (more than 5 ohms). How can I bring it down?

Thanks

 

[petersonra]

Lightning protection systems are generally required to be designed and listed to UL standards and installed by a UL listed contractor. This there would be a drawing that shows the proper installation of this system. Unless you are a listed contractor, you shouldn't be modifying this system.

 

[don_resqcapt19]

The down conductors, in general, must connect to a grounding electrode system that is used only for lightning protection. There is a provision that if the electrical grounding electrode system is a ground ring with rods that meets the requirements for a lightning protection system as found in NFPA 780, it can be used for both the electrical system and the lighting protection system.
In the more common case the down conductors are connected to the lightning protection grounding electrode system and the electrical and lightning grounded electrode systems are bonded together per 250.106.

Note that if you subscribe to LinK for the electronic version of the NEC, you can also access most of the other NFPA standards, including NFPA 780 Standard for the Installation of Lightning Protection Systems

​