Case study: Cost comparison of power feeder installations

The following hypothetical installation compares the installation costs for the three power distribution feeder methods — wire and conduit, power cable and tray and bus duct. For this example, a 100-foot feeder was considered, with two 90-degree bends to feed an 800 A, 480-volt, 3-phase, four-wire panel from a 480volt switchboard. The feeder was routed indoors at 10 feet above the floor. Costs for each installation method were estimated using an industry standard estimating tool.

• The first feeder used three sets of 4#300 MCM copper wire plus #2 ground. Each set was installed in a 2.5-inch rigid galvanized conduit. With this configuration, the material costs come to approximately $10,800 and the labor costs come to approximately $11,300, for a total installed cost of approximately $22,100.
• The second feeder used three sets of four-conductor armored cable installed in cable tray. The cable was modeled as #300 copper with PVC jacket and terminated at each panel. Twelve-inch-wide galvanized steel cable tray was modeled, with appropriate bends, dropouts and end plates. The material costs for this configuration come to $18,100, with labor costs at $4,900. The total for this installation comes to $23,000, similar to traditional wire and conduit.
• Lastly, bus duct was modeled. The bust duct was aluminum with appropriate panel stubs, elbows and an expansion fitting. The costs for this installation came to approximately $62,000 for material and $7,500 for labor, for a total of $69,500 — considerably more than the first two methods.

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