You can use a four-wire thermostat on a two-wire system.
A four-wire thermostat is an outdated model that has been replaced with the latest two-wire model.
The four wires are: G wire, for the fan and is green in color; the R wire, red in color and if used for heating and cooling; Y wire for the compressor and air conditioner, it is yellow in color; and finally W wire for heat, and it is white. The procedure of installing a new two-model thermostat is straightforward and doesn’t need an electrician. You can replace the two by switching off the power supply and then removing the cover from the thermostat by pulling it off or by unscrewing any screws or wiggling one side loose and then wiggling the other side. You can then pull the thermostat out from the wall. Use a flashlight to check the terminals to see which screws are connected to the red and white wires attached to the thermostat. You can then loosen any screws in the terminal block and unwind the four wires from around the screws to remove the thermostat and dispose of it correctly. You can then wind the end of the red wire attached to the replacement thermostat around the screw that held the red wire from the old thermostat. You should then wind the end of the exposed white wire to the white wire attached to the replacement thermostat around the screws used to hold the white wire from the old thermostat. Then tighten the screws on the terminal block. You can then replace your thermostat against the wall and screw the thermostat in place. You can then restore the electricity that powers the thermostat.