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Code Q&A: Conduit Fill Limitations

Test your NEC knowledge.

Q. What is the maximum number of conductors allowed by the Code to be installed in rigid metal conduit (RMC)?

See the answer below.














A. Raceways must be large enough to permit the installation and removal of conductors without damaging the conductor’s insulation. When all conductors within a raceway are the same size and insulation, the number of conductors permitted can be found in Annex C for the raceway type [Sec. 344.22].

Example: How many 8 THHN conductors can be installed in trade size 1½ in. RMC?

Answer: 22 conductors [Annex C, Table C.9]

Cables can be installed in RMC, if the number of cables doesn’t exceed the allowable percentage fill specified in Table 1, Chapter 9.


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