HVAC Procedure and Performance Guide

Check heat-pump cycles (changeover and defrost)

Training for this procedure can be found in these courses:

                         131 – Oil Heat l  and  161 – Boilers l


System must be operated between cycles. Critical operating conditions must be tested to verify that changeover and defrost cycles occur according to manufacturer’s specifications.  System must perform to manufacturer’s specifications in both cycles.  Applicable safety procedures must be followed.


  1. Review manufacturer’s specifications.
  2. Determine operating sequences for heating, cooling and changeover.
  3. Determine critical operating conditions to be measured and where and how to measure them.
  4. Collect tools, equipment and materials.
  5. Put on safety and protective equipment and apparel.
  6. Remove access cover(s).
  7. Connect heat-pump manifold gage set and set up other test instruments.
  8. Start system and allow to stabilize.
  9. Measure critical operating conditions in present cycle.  (Note:  If system is on heating cycle, engage emergency heat and check performance).
  10. Initiate changeover cycle and verify that cycle occurs according to specifications.
  11. Operate system and measure critical conditions.
  12. Check condenser defrost cycle with system on heat and verify that equipment defrosts according to manufacturer’s specifications.  (Note:  Check manufacturer’s instructions and other references for information for special procedures required for testing off-season cycles).
  13. Replace access cover(s).
  14. Leave equipment in required operating status.
  15. Remove safety and protective equipment and apparel.
  1. Gather tools, equipment and leftover materials, and leave work site clean