Setting up fresh-air ventilation on a whole-house ventilating dehumidifier (6 in inlet, damper and ASHRAE 62.2 rate)
Ventilating dehumidifiers have a separate small inlet (6 in on the Ultra-Aire 120H and TrueDRY DR90) for an insulated duct from outdoors. Outdoor air mixes with return air before it is dried and supplied. How much and how often is set by a ventilation control and a damper (manual, or motorized with a digital control). Size the rate from ASHRAE 62.2 as a starting point and set the control's schedule; in humid weather the dehumidifier must run with ventilation or the home will gain moisture.
Before you start
- Unplug the dehumidifier and power off the HVAC system before connecting ducts or damper wiring.
- Keep the outdoor intake well away from vents, exhausts, dryer vents, gas appliance terminations and garages so exhaust gases are not pulled in.
- Low-voltage damper wiring only; never connect the dehumidifier's 24 V terminals to line voltage.
Diagnostic steps
Unlock all 5 steps with expected values
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