I'm installing new double pole thermostats for my baseboard heaters and am stumped on how to wire them properly. The two thermostats I've removed so far have either been wired wrong or single pole.

It looks to me like I have an extra set of wires and I'm not sure how to work them in. In the electrical box, I have a total of three groups of wires:
  • upper left hand - both white and black are hot
  • upper right hand - neither are hot
  • bottom - out to heater

All of the diagrams I've been able to find, have just one incoming set of wires and one outgoing set, so I'm not sure what to do with the extra ones. They were used in the previous wiring scheme.

It's about 10 degrees out, so I'm hesitant to take another thermostat apart until I get things sorted out.

Thanks in advance for any suggestions.