The minimum height permitted for dimension '?' on the drawing, where conduits are 4 in Schedule 40 PVC and contain four 600 kcmil conductors, is ___ inches.

The minimum height permitted for dimension '?' on the drawing, where conduits are 4 in Schedule 40 PVC and contain four 600 kcmil conductors, is ___ inches.

• A. 10 inches
• B. 6 inches
• C. 8 inches
• D. 3 inches

Answer: (A)

The concept being tested is conduit fill and space planning for large feeders in a raceway. When you run four 600 kcmil conductors through a 4-inch Schedule 40 PVC conduit, the space inside the conduit is severely limited. Four such conductors occupy far more cross-sectional area than the conduit can legally or practically carry under the normal 40% fill rule. A 4-inch PVC conduit has an interior cross-sectional area of about 12.6 square inches; the 40% allowable fill cap translates to roughly 5.0 square inches for all conductors. Each 600 kcmil conductor has a cross-sectional area of about 4.7 square inches, so even two or three would already push or exceed the fill limit, making four impossible in a single 4" run. Because of that, the drawing must reflect enough vertical space to accommodate pulling and feasible routing, or to indicate that a larger conduit or parallel runs are required. In the context of this question, the minimum height shown for the dimension is 10 inches, which represents the practical clearance needed to depict or accommodate such a large-conductor installation. The other smaller height options would not provide adequate room for the required fill and pulling considerations.

The concept being tested is conduit fill and space planning for large feeders in a raceway. When you run four 600 kcmil conductors through a 4-inch Schedule 40 PVC conduit, the space inside the conduit is severely limited. Four such conductors occupy far more cross-sectional area than the conduit can legally or practically carry under the normal 40% fill rule. A 4-inch PVC conduit has an interior cross-sectional area of about 12.6 square inches; the 40% allowable fill cap translates to roughly 5.0 square inches for all conductors. Each 600 kcmil conductor has a cross-sectional area of about 4.7 square inches, so even two or three would already push or exceed the fill limit, making four impossible in a single 4" run. Because of that, the drawing must reflect enough vertical space to accommodate pulling and feasible routing, or to indicate that a larger conduit or parallel runs are required. In the context of this question, the minimum height shown for the dimension is 10 inches, which represents the practical clearance needed to depict or accommodate such a large-conductor installation. The other smaller height options would not provide adequate room for the required fill and pulling considerations.