Reply #3: It is simple.

[Wash. state Desk Jet]

old house wiring is too. Pull the old one out -mark the wires so you know which wire goes to which terminal screw .Oh ah, turn off the power to it like it says in the install directions.! Take what you got down to a electrical supply and ask them to set you up with your programmable thermostat. They will show you what you need to know to swap it out.As you know,.some people don't have or know how to use a volt ohm meter. Actually the old twist knob thermostats are not so easily located these days- it has changed to the electronic age.But the wiring is still basic as anyone at a electrical supply will tell you.And they will explain to you why the new type are very cool.

I recently replaced the old twist button style with the same because I did not want somebody to push buttons-I had to go to several different locations to get the old style which means the old style isn't stocked everywhere you can by thermostats.,Actually at ace hardware or true value -is where I located one,a store that still sells those old switches fer the 90 year old houses -stuff like that. If you take the old one with you to the electrical supply-they will fix you up with your new updated one based on the existing wiring and the voltage. Your thermostat has that info. on it although there are only about two types of voltage in the 12 volts 17 volts so on.Unless it's a 110 or 220 volt hard wire such as forced air in wall mount or the base board heat with wall mount thermostat.

Again, it is pretty simple.