I want to install two thermostats in my home, I know how to wire one thermostat. My house has two levels and the t-stat is down stairs. And I want to be able to control the unit from upstairs also. If anyone can help me I will appriciated greatly.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

You could instal a second thermostat upstairs. Run white, yellow, and green wires from the W, Y, and G terminals of the original thermostat to the second one. Disconnect the red wire from the old one, and connect it to the common terminal of a double throw switch. Run red wires from each of the other 2 terminals to each of the R terminals on the thermostats. Which ever thermostat has the red wire switched to it, will control the system.

Thermostats should be on inside walls. If you install the second one directly above the first, it may not be too bad of a job to fish the wires through the wall. The hardest part will be the plates at the top of the lower wall and bottom of the lower wall.

Thank you, so much, for your quick response I will start working on it tonight and let you know how it works out. It might take me a couple of days