What is the maximum number of 12 AWG THWN-2 conductors permitted in a trade size 1/2 RMC conduit, 18 inches in length?

To determine the maximum number of 12 AWG THWN-2 conductors that can fit in a 1/2 inch Rigid Metal Conduit (RMC) with a length of 18 inches, it is necessary to use the NEC (National Electrical Code) guidelines for conduit fill.

The NEC provides tables that specify the allowable fill based on the size of the conduit and the size of the conductors. For a 1/2 inch RMC conduit, the total cross-sectional area available for conductors can be calculated, and the area of one 12 AWG THWN-2 conductor can be referenced from the appropriate NEC table.

The approximate cross-sectional area of a 12 AWG THWN-2 conductor is about 3.31 mm², and the internal cross-sectional area of a trade size 1/2 RMC is about 14.65 mm². This calculation is necessary to ensure that the conductors can be installed without exceeding the fill limits.

By calculating the maximum number of conductors, it becomes apparent that up to 14 conductors are allowed in this conduit size, provided that the conditions for proper installation, such as following de-rating factors and ensuring there is no excessive heat buildup, are