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Most daily calculations for conduit fill are nothing more than a look up. This is true when all conductors are the same size and type. But there may be a need to calculate conduit size when conductors of different sizes and types are expected to be installed in the same raceway. This is not uncommon.

Example: How many #10 THWN conductors will fit in a 1" PVC schedule 40 raceway?

Solution: Go to Annex C of the NEC way in the back of the book. Find the appropriate raceway table. PVC schedule 40 is table C-10. Find 15 at the intersection of THWN and 1' trade size. So 15 will fit. This does not mean you have to use a 1" for 15 conductors. Usually there is some intelligent reason to increase conduit size for large numbers of conductors which travel a long distance. But that is not code. There is no requirement to increase conduit size due to length of run.

Find practice problems HERE. MORE

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For More on Conduit Fill, follow these Google links:

1. Designing Conduit Runs -- calculating fill factor, sizing conduits ...
3. Conduit Fill Conduit Type NEC Tables
4. Conduit Fill Capacity Table
6. Conduit Fill Table Western Extralite Company
7. Fill Calculation
8. Conduit Fill Table
9. Calculating Conduit Capacity
10. Conduit Fill E1.1

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