How much ampacity is allowed for four 14-2 conductor nonmetallic cables (Type NM) passing through an opening in wood framing filled with caulk?

When determining the ampacity allowed for four 14-2 nonmetallic (NM) conductors, it's important to consider the National Electrical Code (NEC) guidelines and how many conductors are grouped together. Under normal circumstances, a single 14-gauge wire typically has an ampacity of 15 amps.

However, when multiple conductors are bundled together as they are here, adjustments need to be made due to derating requirements. Specifically, when conductors are installed in raceways or cables and are bundled together without sufficient airflow, they can overheat. For cables that are passing through openings that are filled with caulk, this can further limit their capacity to dissipate heat.

According to NEC, for cables containing three or more conductors, derating factors apply. In the case of four conductors, there would typically be a 70% derating from the original ampacity. Therefore, if we take the standard 15 amps for the 14-gauge cable and apply the 70% derating factor, the calculation would yield:

15 amps x 0.7 = 10.5 amps

Since there needs to be an adjustment applied for high-temperature environments or certain installations, the most conservative answer that maintains compliance