Bypass vs. Powered Humidifiers
Whole-house evaporative humidifiers fall into two distinct mechanical configurations: bypass humidifiers (which rely on furnace blower pressure differential) and fan-powered humidifiers (which incorporate an independent internal blower fan).
| Feature | Bypass Humidifier (Aprilaire 600) | Fan-Powered Humidifier (Aprilaire 700) |
|---|---|---|
| Operating Mechanism | Diverts air from supply duct through pad to return duct | Draws air directly from supply plenum with internal fan |
| Ductwork Required | Requires 6" round bypass duct connection | Mounts directly onto supply plenum; no bypass duct |
| Evaporative Output | 17 Gallons per day | 18 Gallons per day (delivers warm air across pad) |
| Heat Pump Suitability | Moderate (lower supply air temperatures) | Superior (forced air maximizes low-temp evaporation) |
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Sizing measurements, static pressure curves, and filtration ratings referenced across our educational guides are compiled from published ANSI/ASHRAE Standard 52.2 engineering data, AHAM AC-1 verified ratings, and manufacturer technical documentation. ClariSelect provides objective editorial research and analysis with zero sponsored placements.