Which of the following is a valid major SPD site entrance?

• A. AC Power
• B. Ground Fault
• C. Lightning Surge
• D. Conduit Raceway

Answer: (A)

The main idea is protecting the entire system by placing the surge protection at the point where utility power enters the building. The major SPD site entrance is the AC power entry, typically the service equipment at the building’s main disconnect. Installing the SPD here intercepts large transients before they can propagate through all downstream circuits, keeping the whole system safer and reducing the number of devices needed downstream.

Ground fault is a fault condition, not a physical entry point for power into the building. A lightning surge refers to the source of a transient and is not the location that serves as the entry point for all equipment. A conduit raceway is simply a path for cables, not the point where the main power and all downstream circuits originate. So the AC power entry is the correct major SPD site entrance.