What happens
An unapproved head combination, wrong configuration or insufficient shared capacity prevents the intended zone performance.
Typical symptoms
New or replacement head fails commissioning, or several rooms lose capacity when operated together.
Checks that distinguish this cause
Compare all model numbers, combination tables and load requirements with the approved design. Verify configuration, airflow and charge before concluding that the outdoor capacity is insufficient.
What can look similar
A restricted circuit or sensor problem can cause one room to struggle on an otherwise approved combination.
Repair direction
Correct the established compatibility, configuration or design defect with an approved combination.
Verify the repair
Verify each zone and representative simultaneous demand against the selected-system performance data.
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.