Motor Starter Sizing Guide: Selection Checks

A starter is selected for the motor, switching duty, protection, and control arrangement as a system.

What to confirm

  • Motor nameplate, type, voltage and phase, rated current, starting method, and manufacturer instructions.
  • Starter and contactor ratings for actual load category, operating duty, start frequency, and service conditions.
  • Overload settings, short-circuit and ground-fault protection, disconnecting means, and equipment coordination.
  • Ambient conditions, enclosure, control voltage, interlocks, fault current, and equipment listing.

Selection workflow

  1. Identify required switching, control, and protection functions.
  2. Use manufacturer technical data for the exact model, voltage, load category, duty, and installation conditions.
  3. Check protection separately under locally adopted rules. Ask a qualified professional to review unclear duty, classification, or coordination.

NEMA and IEC ratings

NEMA and IEC are different rating systems. Do not translate size labels between them with a universal horsepower chart. Compare manufacturer data for the exact model and use case. This page provides no starter-size table or protective-device multipliers.

For U.S. installations where adopted, consult the locally adopted edition of NFPA 70, the equipment listing, and manufacturer documentation.