What is the minimum size allowable for a conductor in a circuit with a continuous load at 30 amperes?

In determining the minimum size allowable for a conductor carrying a continuous load, it’s important to refer to the National Electrical Code (NEC), which establishes guidelines for electrical installations. A continuous load is defined as a load that has a duration of three hours or more.

For a continuous load at 30 amperes, you must consider a derating factor to ensure safe and efficient operation. The NEC requires that conductors carrying continuous loads be sized at 125% of the load current. Therefore, for a 30-ampere load, the calculation is as follows:

30 amperes x 1.25 = 37.5 amperes.

Now, we must refer to the NEC Table for allowable ampacities of various conductor sizes. According to the NEC, a 4 AWG copper conductor typically has an allowable ampacity of 85 amperes, which is more than sufficient for a load of 37.5 amperes. In contrast, larger gauge conductors, such as 6 AWG and 8 AWG, have lower ampacity ratings (likely around 65 and 50 amperes respectively), and would not meet the requirements for this continuous load application.

Thus, since 4 AWG is the minimum size that