National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, November 6, 2019

Question:

Thanks for the CQOTD. I've been following it for many years, since Brook was still involved. When a conduit runs consists of two types of conduit, is there anything in the NEC that requires me to use the more restrictive fill table? It seems like common sense, but I was just asked if there is a code reference?

Thank you,

Rich Tomkinson
A

Answer:

Hey Rich thanks for your question and you are welcome, we are pleased to have avid readers. Yes. The raceway fill is based on the type of raceway as indicated by the many different tables in Table 4 and Annex C as stated in Note 1 and Note 6 to Table 1 in Chapter 9. The XXX.22 section for the specific raceway typically refers us to Chapter 9, Table 1. This can result in needing different raceway sizes to not exceed the appropriate percentage of fill of Table 1 in Chapter 9. A simple example is to compare schedule 80 and schedule 40 PVC conduit capacities in Table 4.

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