I want to install a new Nest Thermostat (07/2021 manufactured) and my system has W, Y, G, Rh & Rc wires (Rh-Rc have a jumper and one red wire connected). How do I know if I need a 'C' wire? When I did the compatibility check, I read that my 4-wire system 'may' work with the Nest thermostat.
