What is the ampacity of each 10 AWG copper conductor with 90°C insulation within a 3-conductor Type NM nonmetallic sheathed cable?

The correct answer regarding the ampacity of a 10 AWG copper conductor with 90°C insulation in a 3-conductor Type NM nonmetallic sheathed cable is 30 A.

To understand this, it's important to recognize the factors that determine the ampacity of the conductor. Ampacity is influenced by the size of the conductor, the temperature rating of the insulation, and the number of conductors in a cable.

For copper conductors, the National Electrical Code (NEC) tables provide the ampacity ratings based on the size of the conductor and its insulation type. A 10 AWG copper conductor with 90°C insulation has a base ampacity of 30 amperes according to Table 310.16 in the NEC.

However, when conductors are grouped together, as is the case in a 3-conductor arrangement, adjustments may need to be applied. While this could potentially reduce the ampacity due to factors such as heat dissipation, for three conductors in a nonmetallic sheathed cable, the adjustments are minimal. The 30 A rating remains valid because it does not exceed the adjustment factors applicable for three conductors.

As a result, the 10 AWG copper conductor with 90°C