If six 250 kcmil conductors are housed in a pipe at 129°F, what is the maximum current each can carry?

To determine the maximum current each 250 kcmil conductor can carry when housed in a conduit at 129°F, it's essential to use the National Electrical Code (NEC) ampacity tables that provide the maximum allowable current based on conductor size, ambient temperature, and the number of conductors in a raceway.

For 250 kcmil copper conductors, the base ampacity at a standard temperature (typically 86°F) is around 250 amps. However, as the temperature increases, the ampacity of the conductor decreases because higher temperatures can adversely affect the insulation and overall performance.

At 129°F, you must apply a temperature correction factor from the NEC tables. This correction factor accounts for the increased temperature and can be found in section 310.15 of the NEC. For temperatures above 86°F, the correction factor reduces the base ampacity.

When six conductors are in a conduit, derating also comes into play because of the increased heat generated by multiple conductors sharing the same space. The NEC provides a derating factor for this situation as well. In this case, when applying the temperature correction and the derating factor, the maximum current that each of the six 250 kcmil conductors can