What conductor volume allowance is counted towards the box fill calculation when two internal cable clamps are present in a box?

In box fill calculations, the National Electrical Code (NEC) allows for certain adjustments based on the components that are present inside the box. When two internal cable clamps are used, the volume allowance that is counted towards the box fill calculation is a single volume allowance for the clamps.

Each internal cable clamp serves to secure the conductors and prevent them from pulling out of the box. However, rather than counting each clamp separately as distinct volume allowances, the NEC dictates that only one volume allowance is counted, regardless of how many clamps are present. This is to simplify the calculations and maintain clarity in ensuring that the box is not overcrowded, which can lead to overheating and potential safety hazards.

Therefore, when determining the box fill, it's important to recognize that the presence of two internal cable clamps only necessitates the addition of one volume unit to the overall calculation. This knowledge is critical for adhering to safe electrical practices and ensuring compliance with NEC regulations.