NEC Electrical Exam Prep Question # 157 Pipe Fill Calculations Master Journeyman

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[@MosesMalone-s8f]

NEC 2023 applicable articles:
Conduit size: Ch.9, T4, art. 352
Conductor size: Ch.9, T5
Equation solution:
2.5" PVC SCHED 80 (over 2 wires @ 40% column) = 1.647
#4 THWN = 0.0824
Equation states that there is already (10) #4 THWN conductors in the conduit: 10 X 0.0824 = 0.824
Leftover space within the conduit: 1.647 - 0.824 = 0.85
Out of all the possible answers on the table above, only 10 additional conductors within that conduit would meet the appropriate maximum fill:
10 X 0.0824 = 0.824 = 0.824 < 0.85
(✓)
12 X 0.0824 = 0.9888 = 0.9888 > 0.85 (X)
Both 8 and 9 conductors would fit inside the conduit, but the conduit would have not been filled to its maximum capacity, while using 12 conductors would overfill the maximum permitted fill. Therefore, 10 #4 THWN would be the appropriate amount of conductors to put in a 2.5" PVC SCHED 80 that has already been filled with 10 additional #4 THWN conductors.