Conduit Fill Percent
Conduit Fill Percent
Conduit fill percent is always a comparison of the installed conductors to
the total space in the raceway. Do not make a percent comparison of the
installed conductors to the useful space. This is not correct. But there is more
confusion about this comparison than there needs to be.
Again, to determine the conduit fill percent, use the area of the installed
conductors divided by the total area of the entire raceway.
Fill percentage can not exceed 60% for a nipple of 24 inches or less in
length, and fill can not exceed 40% for a raceway with three or more conductors.
Calculator technique
Find the area of each of the installed conductors in square inches. Add them
together.
Find the total area of the raceway from the table in Chapter 9. Divide the
conductor area by the area of the raceway. The result will be the percent used
by the installed conductors.
