What happens
Zone requests conflict with the system’s permitted heating/cooling selection and priority rules.
Typical symptoms
A head remains in standby while another zone runs, without a proven component failure.
Checks that distinguish this cause
Record every zone’s actual mode, including Auto, and compare the model’s priority and changeover logic. Distinguish intentionally inhibited heads from a lost communication node.
What can look similar
A fault or addressing problem can also stop only one head.
Repair direction
Correct the supported operating settings or design expectation rather than replacing components for normal priority behavior.
Verify the repair
Verify all zones under a permitted shared mode and check the documented changeover process.
Equipment-specific limits
Ordinary heat-pump multi-splits may not heat and cool different zones simultaneously. Heat-recovery VRF has a different architecture. Minimum head counts, capacity ratios and port rules vary.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
References and applicability
Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.
- Senville: R-454B model documentationSeparate installation and service documents for indoor styles and multi-zone generations.
- GREE: GREE communication-fault diagnostic guidanceA GREE-specific example of wiring and board fault isolation; E6 is not a universal code.
Editorial review: 2026-09-29. Verify the current manual for the installed model.