Lightning Arrestor Systems

[ken44]

Is it against the NEC to connect a lightning arrestor system to the grounding electrode. This was recently done by a contractor at a one story commercial office building which we manage? I am under the impression that this could lead to serious equipment damage within the building if all of the voltage from a lightning strike suddenly dumps its power onto the buildings grounding electrode.

 

[bphgravity]

Surge Arrestors (NEC A280) are for premise wiring systems over 1000V, so I doubt this is what you are referring to. Surge Protection Devices (NEC 285) are for premise wiring systems under 1000V and will typically have a connection to the premise wiring grounding system, but I again doubt this is what you are referring to.

Something tells me you are actually referring to a lightning protection system (which should include a SPD). If this is case, the LPS should positively be connected to the premise wiring grounding system. See Section 250.106 of the NEC and Sections 4.13/4.14 of the NFPA 780.

Damage from potential differences may result if the two grounding systems are not bonded together...

 

[GoldDigger]

Surge Arrestors (NEC A280) are for premise wiring systems over 1000V, so I doubt this is what you are referring to. Surge Protection Devices (NEC 285) are for premise wiring systems under 1000V and will typically have a connection to the premise wiring grounding system, but I again doubt this is what you are referring to.

Something tells me you are actually referring to a lightning protection system (which should include a SPD). If this is case, the LPS should positively be connected to the premise wiring grounding system. See Section 250.106 of the NEC and Sections 4.13/4.14 of the NFPA 780.

Damage from potential differences may result if the two grounding systems are not bonded together...

But where and how that bonding takes place is very important too.
Connecting an air terminal to the nearest EGC would be very bad. Connecting the bottom end of a download directly to a ground electrode which is part of the GES would be better but still might not be right.
OP: Read the whole document rather than collecting bits of advice here and there.