Where must surge protective devices be installed?

Surge protective devices (SPDs) are essential for safeguarding electrical systems from transients, such as voltage spikes caused by lightning strikes or other electrical disturbances. The optimal location for these devices is at all power service entrances. This positioning allows them to effectively manage and divert excess voltage right at the point where electricity enters a building, offering the first line of defense against surges that could damage both the electrical system and connected equipment.

By installing SPDs at power service entrances, the devices can protect the entire electrical system downstream, including subpanels, circuits, and individual appliances. This comprehensive protection ensures that any potential surge is mitigated before it can propagate through the wiring and into sensitive electronics.

In contrast, installing SPDs only at subpanels or specific locations would leave parts of the electrical system vulnerable to surges originating from various sources. Placing SPDs inside appliances or limiting them to outdoor settings could result in inadequate protection since these setups would not shield the broader electrical infrastructure. Hence, the best practice is to install SPDs at all service entrances to ensure robust protection throughout the electrical system.