HVAC Procedure and Performance Guide

Replace electric-heater sequencer

Training for this procedure can be found in these courses:

                         131 – Oil Heat l  and  161 – Boilers l


Heater sequencer must be installed according to manufacturer’s specifications. Sequencer contacts must be rated for heater voltage and current.  Sequencer coil voltage requirements must be compatible with control system voltage. Sequencer must have auxiliary contacts as required by application. Sequencer must be securely mounted.  Electrical connections must be mechanically secure and electrical continuity must be established. Sequencer must energize heating elements and auxiliary components as specified. Applicable safety procedures must be followed.


  1. Review job order and manufacturer’s specifications.
  2. Determine voltage and current requirements and number of contacts required.
  3. Collect tools, equipment and materials.
  4. Locate heater sequencer to be replaced.
  5. Put on safety and protective equipment and apparel.
  6. Disconnect electrical power to equipment.
  7. Remove access cover(s).
  8. Disconnect electrical wiring and remove old sequencer.
  9. Verify that new sequencer is suitable replacement.
  10. Mount new sequencer and connect wiring according to manufacturer’s specifications.
  11. Test equipment operation.
  12. Establish air flow across system.
  13. Activate heating system.
  14. Verify that all elements respond to control system and that sequencing is correct.
  15. Verify peripheral equipment controlled by auxiliary contacts respond correctly.
  16. Verify over-temperature safety control functions as specified.
  17. Reconnected electrical power to equipment at correct times.
  18. If system does not operate correctly, troubleshoot and make required adjustments and repairs.
  19. Replace access cover(s).
  20. Leave equipment in required operating status.
  21. Remove safety and protective equipment and apparel.
  22. Gather tools, equipment and leftover materials, and leave work site clean materials, and leave work site clean.