How many No. 4/0 THW copper conductors may be installed in a 2-1/2-inch EMT conduit nipple six inches long installed between a panel and a wireway?

To determine how many No. 4/0 THW copper conductors can be installed in a 2-1/2-inch EMT conduit nipple that is six inches long, one must refer to the National Electrical Code (NEC) and the allowable conduit fill calculations.

First, you need to find the maximum allowable fill for a 2-1/2-inch EMT conduit. According to NEC tables, the total cross-sectional area that can be occupied by conductors in a conduit can be calculated. Each No. 4/0 THW copper conductor has a specific area, which can be found in NEC tables.

For No. 4/0 THW, the diameter is approximately 0.46 inches, which gives a cross-sectional area of about 0.167 square inches per conductor. The total cross-sectional area of a 2-1/2-inch EMT conduit is roughly 4.257 square inches. When calculating for conductor fill, according to NEC guidelines, you cannot exceed 40% of the conduit’s cross-sectional area for more than 2 conductors.

By applying this percentage, the fill calculation shows that you can fit approximately 9 conductors (4.257 sq. in. * 0.