Which option is true about the number of 4 AWG THHN conductors in 11/2" RMC?

Which option is true about the number of 4 AWG THHN conductors in 11/2" RMC?

• A. 8
• B. 9
• C. 10
• D. 11

Answer: (C)

Conduit fill limits how many conductors you can pack into a raceway. For THHN conductors, you add up the cross‑sectional area of all insulated conductors inside the conduit and must keep that total to 40% of the conduit’s interior area. That rule, applied to 11/2 inch rigid metal conduit with 4 AWG THHN, is what the standard fill tables use to determine how many such conductors can fit. The table for this combination shows a maximum of ten 4 AWG THHN conductors in 11/2" RMC. Pushing to eleven would exceed the allowed fill, making it noncompliant. So the best answer is ten. If a grounding or other additional conductor is present, it would count toward fill as well, potentially reducing how many current-carrying conductors can be installed.

Conduit fill limits how many conductors you can pack into a raceway. For THHN conductors, you add up the cross‑sectional area of all insulated conductors inside the conduit and must keep that total to 40% of the conduit’s interior area. That rule, applied to 11/2 inch rigid metal conduit with 4 AWG THHN, is what the standard fill tables use to determine how many such conductors can fit.

The table for this combination shows a maximum of ten 4 AWG THHN conductors in 11/2" RMC. Pushing to eleven would exceed the allowed fill, making it noncompliant. So the best answer is ten. If a grounding or other additional conductor is present, it would count toward fill as well, potentially reducing how many current-carrying conductors can be installed.