In a 4-inch by 4-inch metal wireway, how many 1 AWG THHN conductors can be added if there are twelve 8 AWG THW conductors already present?

To determine how many 1 AWG THHN conductors can fit in a 4-inch by 4-inch metal wireway that currently has twelve 8 AWG THW conductors, we need to analyze the fill capacities based on the NEC (National Electrical Code) guidelines.

First, each wire size has a specific area associated with its cross-section, which is used to calculate conduit fill based on the maximum allowable fill factors. The NEC tables provide the conduit filling capacity for different conductor sizes.

For the THW conductors:

• The area for one 8 AWG THW conductor is approximately 0.628 square inches.

• Therefore, twelve 8 AWG conductors occupy about 12 x 0.628 = 7.536 square inches of the wireway.

Next, we calculate the total area available in the 4-inch by 4-inch wireway. The total cross-sectional area is:

Area = width x height = 4 inches x 4 inches = 16 square inches.

Now, we need to consider the fill capacity. According to NEC guidelines, the maximum allowable fill for conductors in a conduit or wireway is typically limited to 40% of the total cross-sectional area when there are