A box with four internal cable clamps adds how many additional conductors to the fill allowance?

When determining fill allowance for a box with internal clamps, it's important to understand how each component affects the total allowable conductors in that box. The National Electrical Code (NEC) specifies that each internal cable clamp within a box counts as one conductor for the purpose of determining the box fill capacity.

In this scenario, the box has four internal cable clamps. Each of these clamps adds one to the fill allowance, meaning that the total contribution to the fill calculation from these clamps is four. However, the fill allowance for conductors is adjusted based on how many actual conductors are being utilized.

Since the question is asking how many additional conductors the clamps add to the fill allowance, the correct interpretation is that the box essentially accounts for each of the clamps as an extra conductor. Therefore, with four clamps, the adjustment made in filling allowance does not equate to four additional conductors but rather just one additional allowance for the entire set of clamps.

So, the correct answer indicates that despite having four clamps, they incrementally contribute just one additional conductor to the overall fill calculation for the box. Understanding this distinction is crucial when performing box fill calculations to ensure compliance with code requirements and safety standards in electrical installations.