Thermostat Wiring Diagram B. This depends greatly on who installed it as well as who manufactured your heating pump. Use the wiring diagram you got from the compatibility checker in step 4 to connect your system wires to the nest thermostat.
One is for cool and the other is for heat hence the abbreviation rh and rc. The rc terminal is the 24 volt cooling power supply. S1 and s2 wires connects to s1s2 terminals and is for outdoor temperature sensor.
S1 and s2 wires connects to s1s2 terminals and is for outdoor temperature sensor.
Positioning numbered wiring diagrams provided in the honeywell wiring guide. If you have an r rc or rh wire you can put it into the r connector on the nest thermostat. Thermostat wire color code chart. These two connections will ensure that there is power to the thermostat that you are.