What is the ampacity for each of eight No. 2 THWN copper conductors in a single conduit?

The ampacity of conductors refers to the maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration. When dealing with multiple conductors in a single conduit, the ampacity must be adjusted based on the National Electrical Code (NEC) guidelines, which take into account factors such as the number of conductors, the insulation type, and the conduit fill.

For No. 2 THWN copper conductors, the base ampacity is typically determined by referencing the NEC tables. The standard ampacity for a single No. 2 THWN copper conductor in free air may be around 115 amperes, but it must be adjusted when there are multiple conductors in the same conduit.

With eight conductors bundled together, derating factors come into play. The NEC provides a derating table indicating the reduction in ampacity based on the number of conductors in a raceway. For eight conductors, the adjustment might reduce the ampacity significantly.

After applying the relevant derating factor to the base ampacity of the No. 2 THWN conductors, arriving at 80.5 amperes reflects the correct adjustment accounting for conduit fill and thermal dissipation among the conductors.

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