Wiring Nest with 2-stage furnace? - thermostatforums Nov 29, 2017You could run a test at the furnace. Place a temporary jumper between R, W/W1 and W2 to see if the furnace controls react to both heating stages being call for. If the furnace does react to both W/W1 and W2 being called for you should connect them both to the new Nest. You should also connect a C common wire to the Nest. How to Connect the Thermostat to a Two Stage Forced Air A two stage furnace works like this: your thermostat calls for heat and the furnace kicks on low. After a predetermined amount of time, if it has not satisfied the temperature, it kicks up to high until the temperature is satisfied. For this extra stage, you need to connect one additional wire to your furnace and your thermostat.