DESC: The Aprilaire Automatic Humidifier Model 600 takes humidifier innovation to the next level and performs as good as it looks! It offers all of the performance benefits of our other technologically-advanced computer-equipped automatic humidifiers and its easier than ever to have installed because it includes a built-in bypass damper, which means fewer parts to install. Plus, the damper is conveniently labeled for summer and winter settings, allowing you to set it for the entire season with no guesswork involved. Just set it and let your humidifier run automatically and it will deliver up to 50% more humidity, compared to other competitive units on the market. It also can be installed in manual mode if needed. The Model 600 has an evaporative capacity of 0.70 gallons per hour and is ideal for a home with up to 4,000 square feet if its tightly constructed. We believe its the best performing bypass humidifier on the market!