How is volume calculated for multi-gang boxes?

The calculation of volume for multi-gang boxes is based on a standard that specifies how much volume is necessary for accommodating devices and wiring within the box. For each additional device placed in a multi-gang box, a specific volume is added to the total volume calculation. According to the National Electrical Code (NEC), each device is typically assigned an additional volume of 2.0 cubic inches.

This standard ensures that there is sufficient space for the devices and wire connections, which helps prevent overheating and allows for safe and efficient operation of the electrical system. Therefore, when calculating the volume for multi-gang boxes, one must include the base volume of the box itself and then add 2.0 cubic inches for each additional device. This approach is essential for maintaining compliance with electrical safety standards and ensuring proper installation practices.

The other options do not accurately reflect NEC guidelines, as the calculation does require consideration of device volume, and it is incorrect to state that volume calculation is not necessary or that additional devices subtract from total volume. Additionally, while it is permissible to use a single box for multiple devices, each device still contributes positively to the total volume required.