What is the minimum trade size EMT permitted to be installed between two junction boxes that are 5 inches apart, if the run contains thirty-four 8 AWG, twenty 12 AWG, nine 6 AWG, and one 10 AWG THHN/THWN copper conductors?

What is the minimum trade size EMT permitted to be installed between two junction boxes that are 5 inches apart, if the run contains thirty-four 8 AWG, twenty 12 AWG, nine 6 AWG, and one 10 AWG THHN/THWN copper conductors?

• A. 2 in.
• B. 2-1/2 in.
• C. 3 in.
• D. 3-1/2 in.

Answer: (A)

The key idea is how much space the conductors occupy inside a raceway, not the physical distance between boxes. For EMT fill, you count every insulated conductor in the raceway as one unit, and all equipment grounding conductors together count as a single conductor of the largest size present. The size of the largest conductor in this run is 6 AWG, so you convert every other conductor to an equivalent number of 6 AWG conductors using their cross‑sectional area (circular mils). Then you sum these equivalents to get the total number of 6 AWG equivalents that must fit in the EMT. Compare that total to the EMT fill allowances given in NEC tables for different trade sizes. In this case, the 8 AWG and 12 AWG conductors, plus the 10 AWG THHN/THWN, convert to about seventy 6 AWG equivalents when you account for their sizes and quantities, which is within the capacity of a 2 inch EMT. The next larger size would accommodate more, but the minimum size that satisfies the fill is 2 inches.

The key idea is how much space the conductors occupy inside a raceway, not the physical distance between boxes. For EMT fill, you count every insulated conductor in the raceway as one unit, and all equipment grounding conductors together count as a single conductor of the largest size present. The size of the largest conductor in this run is 6 AWG, so you convert every other conductor to an equivalent number of 6 AWG conductors using their cross‑sectional area (circular mils). Then you sum these equivalents to get the total number of 6 AWG equivalents that must fit in the EMT. Compare that total to the EMT fill allowances given in NEC tables for different trade sizes. In this case, the 8 AWG and 12 AWG conductors, plus the 10 AWG THHN/THWN, convert to about seventy 6 AWG equivalents when you account for their sizes and quantities, which is within the capacity of a 2 inch EMT. The next larger size would accommodate more, but the minimum size that satisfies the fill is 2 inches.