Conduit Fill
Definition
The number of conductors installed in a raceway, which affects ampacity derating. More conductors mean less heat dissipation per wire. NEC Table 310.15(C)(1) specifies adjustment factors based on conductor count.
Practical Note
1-3 conductors: no derating. 4-6 conductors: 80% of table ampacity. 7-9 conductors: 70%. Neutral conductors carrying only unbalanced current are not counted in some cases.