Where should Type 3 surge protective devices be installed?

Type 3 surge protective devices (SPDs) are designed to be installed on the load side of branch circuit overcurrent devices. This positioning protects individual circuits from transient voltage surges, such as those caused by lightning strikes or switching operations in the power grid. By placing the SPD on the load side of these protective devices, it allows the surge protector to effectively intercept and mitigate surges before they can damage sensitive electronic equipment connected on that circuit.

This installation approach aligns with best practices outlined in the National Electrical Code (NEC) and various guidance from the industry, ensuring that surge protection is delivered at a critical juncture—just before the electricity reaches the devices and appliances that need safeguarding.

Installing Type 3 SPDs at this location ensures that they provide the necessary protection, while also complying with regulatory standards for safety and performance in electrical installations. This effectively minimizes potential electrical damage to equipment downstream, enhancing overall system reliability and longevity.