What is the maximum number of #10 current carrying conductors allowed in a 1 1/4 inch EMT for general use?

• A. 32
• B. 28
• C. 25
• D. 35

Answer: (B)

Conduit fill limits determine how many conductors can physically fit in a raceway without crowding or overheating. The NEC provides tables that translate a conductor size and insulation type into how much of the conduit’s cross-sectional area they occupy. For a 1-1/4 inch EMT using #10 current-carrying conductors, those tables show you can pack in up to 28 conductors in general-use installations. If you tried to pull more than that, you’d exceed the allowable fill and would need a larger raceway or multiple conduits.

Also remember that when you have more than three current-carrying conductors in a raceway, you must derate the ampacity of those conductors to account for heating. This derating is about how much current the conductors can safely carry, not about how many you can physically fit. Grounding conductors don’t count toward the number of current-carrying conductors for fill calculations, but they still take space and count toward conduit fill.