Model 600M bypass humidifiers deliver up to 17 gallons of moisture per day. Model 600M humidifiers can be plumbed to hot water to improve efficiency in heat pump applications. A manual humidistat is provided with all 600M models; for applications where an automatic control is not practical. AprilAire introduced the first evaporative humidifier for forced air furnace systems back in 1954. Since that time, AprilAire continues to lead the industry in whole home humidification systems. Our evaporative humidifiers work by piping water into the distribution tray located at the top of the humidifier. The water is uniformly distributed across the width of the tray and through a scientifically designed system of outlets. It flows by gravity over the Water Panel evaporator. Dry, hot air from the HVAC system is moved through the moisture-laden Water Panel evaporator. Natural evaporation takes place, the water is turned to vapor, and the humidified air is circulated throughout your home. INCLUDED IN THE BOX: Installation instructions and template, humidifier with built-in bypass damper, 24 VAC transformer, manual humidifier control with sensor, saddle valve, solenoid valve, and Model # 35 Water Panel