What happens
A dirty filter or obstructed ventilation path prevents intended outdoor-air or exhaust flow.
Typical symptoms
Reduced ventilation, increased module noise or a complaint that remains despite satisfactory room cooling.
Checks that distinguish this cause
Identify the fitted module, then inspect its filters and outdoor-air/exhaust paths according to its manual. Measure the prescribed ventilation flow rather than judging from the main cooling fan.
What can look similar
A disabled ventilation command can produce low outdoor-air delivery without a blockage.
Repair direction
Clean or renew approved filters and correct the verified ventilation-path restriction.
Verify the repair
Verify the specified outdoor-air and exhaust operation after service.
Equipment-specific limits
Not every all-in-one unit contains an ERV. Cooling airflow and ventilation airflow are different measurements; use the module’s filtration, balancing and maintenance requirements.
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.
- INNOVA (formerly Ephoca): AIO technical resourcesChoose cabinet style, generation and accessories. Installation, maintenance and troubleshooting documents are separate.
Editorial review: 2026-09-29. Verify the current manual for the installed model.