The thermostat uses 1 wire to control each of your hvac system s primary functions such as heating cooling fan etc.
Thermostat wiring heat pump gas furnace.
My paperback and e book.
S indoor and outdoor wired sensors.
The basic heat pump wiring for a heat pump thermostat is illustrated here.
This originates from the transformer.
Terminal r or terminal rh for the red wire.
For example if the red wire is connected to w on the thermostat the furnace should turn on.
Furnace thermostat wiring diagram terminal letters on a thermostat and what they control the hot wire 24 volts usually red from the transformer is the main power wire to turn on or off a furnace components.
Heating only thermostat wiring diagrams if you only have a furnace such as a gas furnace oil furnace electric furnace or a boiler.
When the red wire is disconnected from w the furnace should turn off.
See the diagram below for what each wire controls on your system.
This way you have a reference.
Y compressor stage 1 cooling y2 compressor stage 2 cooling g fan.
Both the furnace control board and the thermostat will usually have the same terminal letters.