What is the effect of device yokes on box fill?

• A. Device yokes have no impact on box fill.
• B. Device yokes add to the box fill count.
• C. Device yokes only count if metal.
• D. Device yokes reduce the required volume.

Answer: (B)

In box fill calculations, anything that mounts to the box and is carrying current counts toward the available space. The device yoke—the strap or mounting part of a switch or receptacle—takes up physical space in the box, so it must be included in the fill. Each device yoke contributes one conductor-equivalent to the box fill. So when you add a switch or receptacle, you’re increasing the required box volume by that one unit, which is why device yokes add to the box fill count. This is true regardless of the device’s material; the important point is that each mounted device increases the total fill you must accommodate.