Furnace used a Honeywell IQ board that began to fail and stop heating my home in the winter. After a few weeks of studying I came up with this wiring diagram. I decided to replace the IQ board and Honeywell Thermostat with a Nest to continue my home automation set up. This was not an easy task as I needed to pull new wire for the Thermostat, Humidifier, and other components. It was a rewire almost from scratch. I used 8 wire Thermostat wire from Amazon, Purchased the Nest on sale from the power company and the relay from Amazon as well.