ICC Residential Electrical Inspectors Practice Exam

For a single gang receptacle box with specific cable types, how is the total calculated free space determined?

1. By volume of conductors

2. By number of circuits

3. By box dimensions

4. By calculating the sum of receptacle and clamp volumes

The correct answer is: By calculating the sum of receptacle and clamp volumes

The total calculated free space for a single gang receptacle box takes into account various factors that contribute to the box's capacity. When evaluating this capacity, it is essential to calculate the volume of the receptacle, clamps, and any other installed equipment. When determining the total free space, calculating the sum of the volumes associated with both the receptacle itself and any clamps that support the wiring is critical. This is because the receptacle and the clamps take up physical space within the box, which reduces the available free space. The National Electrical Code (NEC) specifies that each conductor within an outlet box must have a certain amount of free space allotted per length of wire, and additional space must be considered for any devices or clamps that are installed. While the other options are relevant to box fill calculations, they do not encompass the complete assessment for determining the free space within the box as comprehensively as the summation of receptacle and clamp volumes does. Hence, focusing specifically on the sum of these volumes provides the necessary guidance to ensure compliance with electrical installation standards, promoting both safety and functionality.