I just moved into a new house that has dual zone electric heat / ac. The thermostat on the top floor had been removed by the previous owner, and there are two sets of wires coming out of the wall. They both have 5 wires, but one has the green wire wrapped back like it wasn't used.

How do I know which set of wires to use? Do I splice the wires together and connect them to the thermostat, or do I need a special thermostat?

It might be that the thermostat was wired to the thermostat on the first floor for easy access to change the temp and u might need an electronic thermostat and if anything else I would call the person you bought it from

I bought a foreclosure, so contacting the previous owner isn't really an option.

The link to the thermostat on the first floor makes sense. I'm assuming if that is the case I'll have to get a special thermostat for the 2nd floor. Any model suggestions? I'll start searching around.

Thanks!