The smallest conduit size allowed to enclose motor terminals from a junction box is?

• A. 1/2 inch
• B. 3/8 inch
• C. 1 inch
• D. 1 1/2 inch

Answer: (B)

The key idea is that conduit size is limited by what physical space is needed to fit the motor’s terminal hardware and the conductors entering it. When you run leads from a junction box to a motor’s terminal box, the conduit must be large enough to accommodate the terminal screws, lugs, and the insulation of the conductors without crowding. For a typical small motor with compact terminals, 3/8 inch provides just enough inner diameter to pass the conductors and allow proper termination and strain relief. A smaller size would not clear the terminal hardware, making a proper connection impossible. Larger sizes are permissible but unnecessary for this minimal case, though they’re used when more conductors or bigger leads are involved.