My two old Lux Pro PSP511LC are dying (LCD going out on both!) so I got two new thermostats from a friend he didn't need we both thought I could use. They are the Orbit Clear Comfort 83521 thermostat. My heating system (no cooling) is simple: Oil burner furnace in the basement and radiation with two thermostats, one on each floor, of the house. There are two zones or circuits (not sure about the terminology), one for each floor, and the current Lux Pro's are wired exactly the same on each floor and works fine. I contacted Orbit and they said that since I have two floors/zones the Orbit won't work. I didn't really understand why but they said it's a "single stage" thermostat, but it looks like my current Lux Pro thermostats are exactly the same in this regard and works totally independent of each other. If someone could clarify this for me it would be great.I could go and get new Lux Pro's, but since I got the Orbits given to me it would be good if I could put them to use.
The Lux Pro Thermostat here: Lux Pro PSP511LC
The Orbit thermostat here: Orbit 83521