What is the maximum conduit fill percentage?
NEC Chapter 9, Table 1 sets the limits: 53% for a single conductor, 31% for exactly two conductors, and 40% for three or more conductors. The two-wire case is the strictest because of how conductors pack. These percentages keep pulling tension and heat dissipation reasonable; exceed them and you risk damaging insulation during the pull.
Answers
- How many wires can I put in a 1/2-inch conduit?
- Does the ground wire count in conduit fill?
- Does conduit fill include insulation thickness or just copper?
- What if my conduit fill is over 40 percent?
- Does a short conduit nipple really allow 60 percent fill?
- Do spare conductors count toward conduit fill?