Four 3/0 AWG THWN conductors, each 0.2679 square inch in area, are pulled into rigid metal conduit. What is the minimum trade size?

解析

Total conductor area is 4 x 0.2679 = 1.0716 square inches, and with more than two conductors only 40 percent of the raceway may be filled. One and one-half inch RMC allows only about 0.81 square inch at 40 percent, which is too little, while 2 inch RMC allows about 1.34 square inches and is adequate. Two and one-half inch is larger than the calculated minimum.