A solar contractor is installing a new PV system on a residential property. The inverter output circuit is rated at 25A. The conductors for this circuit will be run in a conduit through an attic space where the ambient temperature can reach 45°C (113°F). The conductors used are copper with 90°C insulation. According to the National Electrical Code (NEC), what is the minimum required ampacity for these conductors after applying temperature correction and continuous load adjustments?

Correct answer: D. 31.25A

First, the continuous load adjustment: PV inverter output is a continuous load, so the circuit's overcurrent protection must be sized at 125% of the continuous current (25A * 1.25 = 31.25A). This means the conductors must have an ampacity of at least 31.25A *before* temperature correction. Next, temperature correction: For 90°C conductors in 45°C ambient, NEC Table 310.15(B)(2)(a) (formerly 310.16) shows a temperature correction factor of 0.82. To achieve a required ampacity of 31.25A after correction, the conductor's ampacity from the table must be 31.25A / 0.82 = 38.11A. Looking at 90°C column in NEC Table 310.16: 10 AWG copper is 40A. So, 31.25A is the minimum required ampacity *after* all adjustments.