• M3 Select-Control Manual Humidistat is included. • GENERALAire’s highest capacity model delivers 23 GPD and is ideal for today’s larger homes. • Replacement pad part number 1099-20. • A portion of the heated air from the furnace passes through a water-soaked pad where it absorbs additional moisture and then returns for distribution throughout your home. • Water is metered into a patented trough and dispersed uniformly across the pad. Unevaporated water drains from the bottom of the unit to eliminate mineral build-up.