What is the maximum number of 10 AWG THW-2 conductors that can be added to a trade size 1 EMT raceway containing eight 12 AWG RHH conductors?

To determine the maximum number of 10 AWG THW-2 conductors that can be added to a trade size 1 EMT raceway already containing eight 12 AWG RHH conductors, it is essential to refer to the conduit fill calculations specified in the National Electrical Code (NEC).

In a trade size 1 EMT, the internal fill capacity is measured in cubic inches. Each conductor type has a specific fill requirement measured in cubic inches based on its size and insulation. For this example, the fill for 12 AWG RHH conductors is approximately 0.244 cubic inches per conductor, while 10 AWG THW-2 conductors require about 0.328 cubic inches each.

First, calculate the fill occupied by the existing eight 12 AWG RHH conductors:

[

\text{Fill for 12 AWG} = 8 \text{ conductors} \times 0.244 \text{ cu in/conductor} = 1.952 \text{ cu in}

]

The volume of a trade size 1 EMT is about 5.24 cubic inches. To determine the remaining capacity, subtract the fill used by the existing conductors from the total volume