I recently purchased a Robertshaw Thermostat, it is not battery operated, but it is 24 VAC Powered. Well the wiring that comes out of my wall only has 4 wires, but I heard that I need 5 wires to make that thermostat work. Can you let me know if that is true or not. If it is true is there any way I can just use four wires? Please let me know?

Old thermostat brand and model number?

New thermostat model number?

It is a good possibility you will have to add another wire.