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A residential circuit is to be wired with 10 AWG THWN-2 copper conductors. The conduit is 1-inch diameter. What is the allowable fill of the conduit?

Texas Master exam practice question · Wiring Methods

A residential circuit is to be wired with 10 AWG THWN-2 copper conductors. The conduit is 1-inch diameter. What is the allowable fill of the conduit?

  • A70% of the conduit area
  • B60% of the conduit area
  • 50% of the conduit area
  • D40% of the conduit area

Exam tip

Remember that conduit fill calculations are based on the size of the conduit and the number of conductors, as specified in NEC Article 318.

Why C is correct

According to 2026 NEC Article 318.8, the allowable fill for 10 AWG conductors in a 1-inch conduit is 50% of the conduit area. The other options are incorrect as they do not meet the requirements specified in the NEC.

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