What is the minimum Size for Single Line SPD?

• A. #8 AWG
• B. #10 AWG
• C. #12 AWG
• D. #14 AWG

Answer: (B)

Understanding why this matters starts with how SPDs are protected: the wire feeding or connected to a Surge Protection Device must be able to carry the surge current long enough for the protection to do its job, without overheating or degrading the installation. That means the conductor’s ampacity matters, not just its voltage rating or physical size.

For a single-line SPD installation, a copper conductor sized to 10 AWG meets the needed balance of safety, reliability, and practicality. It has enough ampacity to handle the surge current and the associated heating that can occur during a transient event, while remaining cost-effective and installable. Smaller gauges, like 14 AWG or 12 AWG, would typically not meet the necessary ampacity for these surges and could overheat or require additional protective measures. Larger gauges, while more robust, aren’t required for this scenario and add unnecessary expense.

So, the minimum acceptable size for a single-line SPD conductor is 10 AWG copper.