I bought a universal digital thermostat that has a 2-wire section. I want to piggy back this T-stat off my existing T-Stat in my living room for my 20+ year old Carrier Central heat/cool system. It will simply turn on the fan only and not the heat from the Central furnace. The fan wire on the furnace is also hooked to the pump on the outside wood furnace so it comes on when the fan comes on. Can I hook/add a wire from the G terminal (fan) and the R terminal (24 volt) on my existing T-Stat to the G terminal and Rh terminal on the new T-Stat to run the fan only? Do I need to disconnect any wires from the existing thermostat to do this and can the existing thermostat stay in the off mode? Or does the existing T-stat need to be on the fan only mode? Any other info would be appreciated.