Aprilaire 1750A, 1770A How Does the Dehumidifier Work?, How Does the Optional Ventilation Work?

Optional – Convertible Mode: Whole Home and Spot Dehumidification

The dehumidifier can be installed to dehumidify the whole home and separately dehumidify a spot location such as a basement or crawl space. In this arrangement ductwork connects the dehumidifier to the heating and cooling system and to the spot location. Dampers in the ductwork are opened and closed to direct where air is drawn from and to where it is sent. One example of how this might look is shown to the right (if you are unsure of whether your dehumidifier has been installed for Convertible operation, contact your installing contractor).

If installed in Convertible configuration, the dehumidifier turns on and opens/ closes the dampers to dehumidify the whole home the first time that the blower in your home heating and cooling system turns on within the Cycle Period. If not actively dehumidifying the whole home three minutes before the end of the Cycle Period, the dehumidifier will turn on and open/close dampers to dehumidify the spot location. If your dehumidifier is actively drying the whole home at the end of the Cycle Period, spot dehumidification is put off until the next Cycle Period.

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How Does the Dehumidifier Work?

When the dehumidifier turns on, the blower circulates the air for three (3) minutes before measuring the humidity level of the air. The green status light below the control setting flashes when the dehumidifier is circulating the air. If the humidity of the air is higher than the setting, the compressor turns on and the green Status light is lit continuously. The dehumidifier turns off after the humidity level of the air has dropped below the setting.

Optional – Heating and Cooling System Blower Operation

Your installing contractor may have configured the dehumidifier to turn on the heating and cooling system blower when the dehumidifier turns on to allow for improved circulation of the dry air.

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How Does the Optional Ventilation Work?

With the ventilation option installed (if you are unsure if this option has been installed, contact your installing contractor), the dehumidifier will bring in outside air for the amount of time set on the Cycle Time adjustment during the set Cycle Period.

Your dehumidifier will work with your heating and cooling system blower to satisfy the ventilation requirements that have been set. For example, if the Cycle Time is set for 20 minutes and the Cycle Period for 1 hour, you will get outdoor air introduced to your home for 20 minutes every hour. When your heating and cooling system blower operates the dehumidifier blower will turn on and will open a normally-closed damper in the duct that brings in outdoor air. If it is getting close to the end of the Cycle Period and your heating and cooling system blower has not operated, the dehumidifier will turn on the system blower. Using the 20 minute per hour settings as an example, if the heating or cooling comes on for only 10 minutes, the dehumidifier control will turn on the system blower for the final 10 minutes of the 1-hour cycle period to deliver the required amount of fresh air.

Outdoor air that is brought in will mix with the air circulating through your heating and cooling system. The dehumidifier will continuously monitor the mixed air and if the humidity level gets higher than the setting, it will turn on the compressor to remove the moisture.

An outdoor sensor, if installed with the ventilation option, will monitor the temperature of the outdoor air and if the temperature exceeds 100°F (38°C) or drops below 0°F (-18°C) ventilation will not occur. If the outdoor temperature is between 20°F (-7°C) and 0°F (-18°C), ventilation will only occur when your heating system operates.

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