What is the ampacity of three 3/0 AWG THHN copper conductors installed in rigid nonmetallic conduit with a 90°C rating?

To determine the ampacity of three 3/0 AWG THHN copper conductors installed in rigid nonmetallic conduit with a 90°C rating, we refer to the National Electrical Code (NEC) table that specifies wire ampacities based on conductor size, material, insulation type, and installation conditions.

For THHN copper conductors, the ampacity is primarily determined by the insulation type and temperature rating. At 90°C, the ampacity for a single 3/0 AWG copper conductor is typically 200 amperes. However, when multiple conductors are installed together, as in this case where we have three conductors, we need to apply the appropriate correction factors.

According to NEC guidelines, when two or more conductors are installed together, the total ampacity has to be adjusted due to the heat buildup associated with multiple conductors. Specifically, for three conductors, there is not an adjustment factor needed for three conductors under normal conditions within a conduit.

Given these considerations, each 3/0 THHN conductor maintains its rated ampacity of 200 A. Since this is a system of three conductors, and we are looking for the ampacity of one conductor and not the combined load, it