Where should surge protection be installed in relation to a feeder entering a building?

Surge protection should be installed at the building's main service entrance because this location serves as a critical point where the electrical service enters the building. By placing surge protection at this point, it effectively guards the entire electrical system and all connected devices from voltage spikes and surge events that can occur due to lightning strikes, utility switching, or other sources.

Installing surge protection here ensures that any overvoltage conditions are intercepted before they can propagate into the electrical distribution system of the building. This proactive measure helps to minimize the risk of damage to sensitive electronic equipment and provides a higher level of safety for the overall electrical infrastructure.

Installing surge protection at the transformer would only protect the downstream side from surges originating upstream, which may not be sufficient for greater protection of the building’s internal systems. Placing it only at the sub-panel is inadequate, as this would not protect the entire electrical system from external surges. Neglecting surge protection altogether can leave the facility vulnerable to damage from power surges, which can result in costly equipment repairs and downtime.