Can SPDs be grounded through a down conductor of the lightning protection system?

Grounding surge protective devices (SPDs) through a down conductor of the lightning protection system is not advisable. The primary reason for this is that SPDs are designed to protect electrical systems from transient overvoltages caused by lightning or other electrical surges. When an SPD is connected through a down conductor, it can compromise the integrity and function of the lightning protection system itself.

When SPDs are grounded improperly, there is a risk that the surge currents could return to the lightning protection system rather than being safely dissipated into the ground. This can lead to potential overloads or failures in the lightning protection components, undermining their capacity to safeguard the structure. SPDs should have an independent grounding system that ensures effective operation and does not interfere with the lightning protection system’s grounding.

In summary, SPDs should not be grounded through the down conductor of a lightning protection system to maintain the safety and efficacy of both the surge protection and the lightning protection systems.