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error Aprilaire
Error Code Solid red Fill Light
Indicates an obstruction that keeps the humidifier from filling correctly.
? What Causes This
High static pressure in ductwork causing backpressure, or issues with fill hose connection/positioning.
✓ How to Fix It
Ensure steam hoses have stable downward slope; inspect and correct high-pressure discharge situations in dispersion tubes.
Source: page 27 of the official manual
From the manual
This error code appears in:
Aprilaire 800