How do I connect my whole house humidifier to my furnace? How do I connect my whole house humidifier to my furnace? Ask Question Asked 4 years, Connecting Desert spring Humidifier to the furnace: Do I eliminate the 24V transformer that came with it? The furnace Keeprite has the the electronic board says Humidifier W1 and C. Wiring humidifier to furnace fan. 0. wiring - How do I wire a humidifier without a 24 VAC IN The instructions for the humidifier I'm installing says to connect the humidistat wiring to the two terminals "marked 24 VAC IN". My furnace doesn't have terminals marked that. I have R,C,W,Y.G.