The table, not the nameplate

You'd think you size a motor circuit from the motor. You don't. You size it from a table — NEC Table 430.250 — and the code is blunt about it: 430.6(A) says use the table values for the conductors, the breaker and the disconnect, even when the nameplate says something else.

Why a table beats the nameplate

The nameplate current changes with every manufacturer, efficiency class and rebuild. The circuit doesn't get rebuilt when the motor does — next year someone swaps in a different 10 HP motor, and the wiring has to already be right. The table is the planning constant: one agreed number per horsepower and voltage, deliberately on the safe side.

Here's the 10 HP row:

One motor, three very different currents — voltage decides how hard the wire works. (That idea gets its own lesson at the end.)

System voltage vs motor voltage

The table's columns are motor nameplate voltages, slightly below the system that feeds them: a 480 V system drives a 460 V motor, 240 V drives 230 V, 208 V drives 208 V. You read the column for the motor, not the panel. The designer handles the mapping for you.

The one exception

The nameplate keeps exactly one job: setting the overload. That's the device protecting this specific motor, so it follows the actual iron bolted to the floor. Everything else follows the book.

Run it

Open the cooling-water pump — a 10 HP motor on 480 V — and tap the motor at the bottom of the one-line. FLA reads 14 A, straight off the table. Now change the system voltage to 208 V and watch every element upstream re-size itself. That chain reaction — one table value driving five decisions — is the whole course.