A little lever near the furnace says Summer on one side and Winter on the other. Before moving it, identify what it belongs to. A whole-home humidifier's bypass damper is different from an HRV control, a fresh-air opening or a damper that serves a room.
The lever and the humidity setting have separate jobs
Source: AprilAire: summer shutdown varies by humidifier and control
A bypass humidifier uses an air path connected to the duct system. Its seasonal damper changes that path. The humidity control decides when the humidifier is being asked to add moisture. Adjusting one is not necessarily the complete seasonal routine.
AprilAire's instructions, for example, call for closing the bypass on its 400, 500 and 600 series during summer shutdown. Its other humidifier types and different automatic or manual controls have different instructions. That example should not be copied onto an unidentified installation.
Read the manual for both the humidifier and the control. Check any installer label against those documents. Some automatic control arrangements need no seasonal dial change; a blanket instruction to turn every control off would miss that distinction.
Make the next change easy to identify
- Record the humidifier model and the control model.
- Photograph the normal winter and summer positions described in the instructions.
- Check whether the water supply, cleaning or other maintenance is part of the seasonal procedure.
- Keep the instructions with the home's equipment record.
Use only the normal accessible controls. Do not force a stiff lever, remove a damper plate or reach into ductwork to confirm its position. A damaged linkage or unclear installation label is a reason to ask the installer to identify the arrangement.
If the manual calls for closing a water valve, identify the correct valve and follow that procedure. A valve that leaks or will not operate needs attention; it is not something to compensate for by turning the humidity dial lower.
Recheck the arrangement before heating season
When humidification is needed again, follow the model's return-to-service steps, including its panel or canister maintenance. Restore the required bypass and control settings, then check normal operation and watch for leaks.
If summer indoor air remains damp, investigate moisture sources, cooling and ventilation. The seasonal lever is one equipment setting, not a diagnosis or a substitute for dehumidification.
