Type 3 surge protective devices must be installed at least how far from the main distribution panel?

Type 3 surge protective devices (SPDs) are designed to be installed at the service entrance or, in some cases, near the equipment being protected. These devices are intended to protect against transients from external sources, such as lightning or utility switching, as well as smaller transients from electrical devices within the installation.

The requirement for a minimum distance from the main distribution panel, which is set at 100 feet, is based on practical and safety considerations. This distance helps ensure that the surge protective devices can adequately protect sensitive equipment without significant risk of voltage rise due to impedance in conductors. When SPDs are installed too close to the main panel, they may not be effective in preventing the transmission of electrical surges to downstream devices, which could result in damage.

Installing the Type 3 SPDs at least 100 feet away from the main distribution panel allows for a broader electrical protection zone, ensuring that harmful transients are mitigated before they reach sensitive equipment. It also reduces the risk of back feed issues and enhances the overall effectiveness of the surge protection system.

In summary, the specification that Type 3 surge protective devices must be installed at least 100 feet from the main distribution panel is designed to optimize their functionality and ensure reliable protection against