User Manual for Aprilaire 1870 and 1870W Dehumidifier

Quick guide from the manual

The Aprilaire 1870 and 1870W are whole-home dehumidifiers designed to control humidity levels. Upon initial installation, set the humidity to 55% RH. Allow the unit to run until it reaches the setting before making adjustments. The unit is not designed to prevent window condensation in winter; use ventilation for that purpose. If you are leaving for an extended period in summer, set the RH to 55% and adjust your thermostat to a comfortable level for your home.

Product overview

The dehumidifier consists of a cabinet containing a blower, a sealed refrigeration system, and a drain pan. Air is drawn into the inlet, filtered, dehumidified, and discharged through the outlet. The control panel features an ON/OFF button, MODE button for ventilation, and UP/DOWN buttons for humidity settings.

Setting the desired humidity level

The on-board control displays the humidity setting when the unit is idle and the measured humidity when running. Use the UP and DOWN buttons to adjust the relative humidity between 40% and 80%. If you prefer drier air, decrease the setting; for less dry air, increase it. Note that the home acts like a sponge, so the unit may run for an extended period when first installed to remove moisture from building materials.

How the dehumidifier works

The unit measures humidity once per hour. If the humidity is higher than the setting, the compressor turns on. The unit continues to dehumidify until the level is 3% RH below the setting. When the unit turns on, the blower circulates air for 3 minutes to sample the humidity before the compressor engages. The display will show AIR SAMPLING or DEHUMIDIFYING accordingly.

External control options

The dehumidifier can be controlled by optional external controls such as the Aprilaire Model 76, 8620, or 8910. The Model 76 acts as a dedicated control and remote, while the 8620 and 8910 integrate dehumidification into the thermostat. Refer to the specific owner's manuals for these controls for operating instructions.

Optional ventilation

If installed, the ventilation feature brings fresh air into the home. To adjust the ventilation time, press the MODE button twice to display the ventilation setting. Use the UP or DOWN buttons to set the minutes per hour (0-60) that ventilation should run. Setting it to zero turns the feature off.

Maintenance

The air filter should be checked and cleaned every 6 months. When the CLEAN FILTER reminder appears, press the UP and DOWN arrows simultaneously for 3 seconds to clear it. To clean the filter: turn the unit OFF, remove the access door, slide out the filter, wash with warm water and mild detergent, dry, and reinstall. The drain system should also be checked annually for blockages.

Troubleshooting

The on-board control displays diagnostic codes if service is required. If E1–E7 or E9 appears, contact your installing contractor. The E8 code indicates that the incoming air is below 50°F or above 104°F, or the dew point is below 40°F. The unit will resume operation automatically once conditions return to the acceptable range.