All of the following copper wires are to be installed in an electrical metallic tubing that is 10 ft long. What is the minimum trade size of EMT required?

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

Answer: (A)

Conduit size is determined by how much space the conductors occupy inside the raceway. The NEC limits how much of the EMT’s interior can be filled with copper conductors and their insulation, plus the grounding conductor and any internal fittings. As you add more or larger conductors, the required cross‑sectional area grows, and smaller EMT sizes can become overfilled, making pulling them through difficult or impossible. For this particular run, the combination of copper conductors would exceed the allowable fill in the smaller EMT options, so you must step up to a larger trade size to fit them with room to spare. The smallest size that meets that requirement is two inches, which is why that choice is the correct minimum. The larger sizes would also work but aren’t needed to satisfy the fill limit, while the smaller options would not physically accommodate the conductors.