Is it acceptable for two downleads to be spaced closer together than 100 feet?

The principle behind the requirement for downleads to be spaced at least 100 feet apart is grounded in the concept of providing effective lightning protection. When downleads are positioned too closely, they can create a situation where the protection system's effectiveness is compromised. Closer spacing can lead to issues with electromagnetic interference and promote the risk of ground potential rise or the formation of step voltage within the protective system.

By maintaining a distance of at least 100 feet between downleads, the system ensures that the electrical energy from a lightning strike is effectively dissipated into the ground without creating a concentrated point where energy might travel through unintended paths. This separation helps in maintaining the integrity of the ground potential rise and minimizes the chances of side flashes, which can happen if the downleads are too close to each other.

Understanding the necessity of this spacing is critical for achieving optimal performance from the lightning protection system and ensuring the safety of the structures and personnel involved.