Thermostat Wiring For Furnace And Ac

The white wire underneath your thermostat connects to your heating system.

Thermostat wiring for furnace and ac.

Flip the furnace ac breaker to the off position. Check to see if they match the industry standard listed above. The white wire connects to terminal w in industry standard thermostats. That will power the relay contactor or complete the circuit in the circuit board.

Breakdown of colors and terminals thermostat wiring diagram for ac unit. The yellow wires underneath your thermostat connect to your compressor. They control your air conditioning system. This diagram is to be used as reference for the low voltage control wiring of your heating and ac system.

Sometimes depending on the thermostat and the manufacturer the thermostat can be a dual heat pump thermostat. The yellow wires connect to the y terminals on your thermostat. G terminal to the green wire. Always refer to your thermostat or equipment installation guides to verify proper wiring.

The yellow wires terminate at your compressor contactor via an air handler. It terminates at your air handler or furnace. Thermostats use 24 volts ac from a transformer to control a furnace. W terminal to the white wire.

The heating system will likely be a gas or electric furnace. Notesome ac systems will have a blue wire with a pink stripe in place of the yellow or y wire. The two 24 volt wires go to the r terminal and c terminal inside the thermostat. The transformer steps down 120 volts to the 24 volts the thermostat needs and sends out the 24 volts on two wires.

In the most basic system this functionality is provided by use of a fan center relay and the low voltage wiring to the thermostat now will require a minimum of three wires for heat only. Label where the wires are connected on the thermostat. R terminal for the red wire. Or it can be used for an air conditioner and gas furnace system depending on how the thermostat is wired.

Additionally it will require a different thermostat and different wiring than an air conditioner. A thermostat with five wires typically controls an air conditioner with a heating system. The thermostat is likely a digital thermostat that requires the c wire or the common wire to provide power for the thermostat. This function allows you to circulate the air in the house by using the fan in the furnace without heating or cooling the air moving through the system.

Once your c wire is ready follow these steps to install your new thermostat. C terminal to the blue wire. Red wire for air conditioner control power hot 1 the r terminal is the 24 volt hot feed from the control step down transformer.