What does the NEC specify regarding the installation of internal cable clamps in a box?

The National Electrical Code (NEC) specifies that internal cable clamps in a box count as one volume allowance. This is important for ensuring that electrical boxes are adequately sized to accommodate the conductors and devices contained within, which can help prevent overheating or other electrical hazards.

When calculating box fill, every conductor, device, and fitting needs to be accounted for so that the box can safely accommodate all components without overcrowding. The inclusion of internal cable clamps is treated as a single volume allowance, which simplifies the box fill calculations and ensures compliance with sizing requirements outlined in the NEC.

Understanding that internal cable clamps count as one volume allowance helps electricians and contractors accurately determine the correct size of electrical boxes needed for their installations, ensuring safety and adherence to code provisions.