HVAC Procedure and Performance Guide

TASK: Connect three-phase motor

Training for this procedure can be found in these courses:

                         131 – Oil Heat l  and  161 – Boilers l


Motor must be connected to specified power source.  Connections must be mechanically secure and electrical continuity must be established.  Motor must operate at specified RPM and must rotate in specified direction.  Equipment must have code-approved ground.  Applicable safety procedures must be followed.


  1. Review manufacturer’s specifications and wiring diagrams.
  2. Determine required voltage, motor current and motor speed from manufacturer’s nameplate.
  3. Collect tools, equipment and materials.
  4. Put on safety and protective equipment and apparel.
  5. Check equipment that motor will operate and establish specified direction of rotation.
  6. Determine if power supply to motor is correct voltage and wire size. (Note: Ensure that electrical power is disconnected from wiring to be handled.)
  7. Test motor windings for shorts, opens and grounds.
  8. Connect three power leads to motor terminals according to manufacturer’s specifications. (Note: Install and test equipment ground.)
  9. Start motor and check direction of rotation. (Note: If rotation is incorrect, stop motor and switch any two leads.
  10. Install motor-terminal box cover(s).
  11. Restart motor.
  12. Measure phase voltage & current and compare to nameplate data.
  13. Check for faulty windings if current readings are too high.
  14. Check starters and breakers if voltage readings do not match specifications. (Note: If there are no faults in switch gear or motor, check with electric power company for assistance.)
  15. Leave equipment in required operating status.
  16. Remove safety and protective equipment and apparel.
  17. Gather tools, equipment and leftover materials and leave work site clean.