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Series H:
Determining Amperage

Determining Amperage: - The national electric code suggests the following when determining motor amperage loads:
  1. For one motor, use 100% of motor nameplate full load ampere rating.

  2. For multiple motors on a single crane or hoist, the minimum circuit ampacity of the power supply conductors on a crane or hoist shall be the nameplate full load ampere rating of the largest motor or group of motors for any single crane motion, plus 50% of the nameplate full load ampere rating of the next largest motor or group of motors.

  3. For multiple cranes and/or hoists supplied by a common conductor system, compute the motor minimum ampacity for each crane as in step (2), add them together and multiply the sum by the demand factor from the following table:

    Number of cranes 2 3 4 5 6 7
    Demand factor .95 .91 .87 .84 .81 .78

  4. For constant loads such as magnets, lights and air conditioners, etc., plus high duty cycles, use full load amperage in selecting conductor size.