What is the ampacity of two 8 AWG THWN-2 copper conductors installed in rigid metal conduit at an ambient temperature of 86°F?

To determine the ampacity of two 8 AWG THWN-2 copper conductors installed in rigid metal conduit at an ambient temperature of 86°F, it is essential to refer to the National Electrical Code (NEC) ampacity tables, particularly Table 310.16.

For 8 AWG copper conductors rated for THWN-2 insulation, under standard conditions of a maximum ambient temperature of 86°F, the base ampacity is typically 50 amps. Since two conductors are being used, and considering that they are inside rigid metal conduit, you apply the appropriate adjustment factors that may affect the ampacity due to conduit fill and the number of conductors.

In the case of two conductors, the ampacity does not change significantly, and the base amperage as indicated for two conductors remains close to the maximum ampacity stated. The adjustment factors may lead you to consider a slight increase due to the thermal management properties of the rigid metal conduit, as it can assist in dissipating heat better than other types of conduit.

Therefore, for two conductors and at the specified temperature, the most accurate ampacity value that corresponds to the adjustments and conditions described remains at 55 amps. This makes it the most appropriate answer