Question

Three electric heaters have a line current of 35 amperes each. Each heater is connected to one phase and a grounded conductor. The six conductors are required to be what size THHN?

a. No. 10

b. No. 8

c. No. 6

d. No. 4

Answer 1

The size of the THHN wire required for the three electric heaters is No. 6.

Step-by-step explanation:

The size of the THHN wire required for the three electric heaters can be determined by considering the current-carrying capacity of the wire. The line current for each heater is 35 amperes. Since there are six conductors in total (three heaters each with a phase and grounded conductor), we need to find the wire size that can handle a total current of 35 amperes for six conductors.

Based on the American Wire Gauge (AWG) standards, we can refer to a wire ampacity chart to determine the appropriate wire size. In this case, we need a wire that can handle at least 35 amperes, so we would look for a wire size with a higher ampacity. From the available options, No. 6 THHN wire has an ampacity of 55 amperes, which is sufficient to handle the total current of 35 amperes for the six conductors.

Therefore, the correct answer is Option c. No. 6.