What is the maximum annular space allowed between a listed electrical box and a two-hour rated wall without requiring penetration protection?

The maximum annular space allowed between a listed electrical box and a two-hour rated wall is 1/4 inch. In many codes and standards, including the National Electrical Code (NEC), this requirement is based on fire safety considerations. The purpose of limiting the annular space is to minimize the potential for fire and smoke to spread through gaps around electrical boxes. When the gap is kept within the specified maximum dimension, the box maintains the fire-resistance rating of the wall, meaning it can continue to provide an effective barrier against fire for the designated time period.

If the annular space exceeds the limit, additional firestop protection would be necessary to maintain compliance with safety standards. It's essential to adhere to these specifications to ensure both safety and code compliance in electrical installations.