I recently bought a new thermostat from Honeywell, model VisionPro TH8320. I'm replacing the old thermostat MapleChase 9620 (now Robertshaw 9620). The old one was working correctly. It has 7 wires. I believe I figured how to wire 5 of them, but not sure about the remaining two. I tried different combinations, but it always gives me heat instead of cold.

Based on Robertshaw 9620, my configuratioon is a typical heat pump with cool active reversing valve and auxiliary/emergency heat. 7 wires has following code: C (24V common), R (24V hot), Y1 (first stage compressor), E (emergency heat), G (indoor fan), W2 (second stage heat), O (cool active reversing valve).

Based on this wire, I figured my system must be a 2H/2C system (1 transformer), becase only this one has 7 wires based on instruction of TH8320. Is it right?

I found the matching terminor at TH8320 for C (24V common), R (Power, with jumper to RC), G (fan relay), W2 (heat relay 2). I connected Y1 (first stage compressor) from MapleChase to Y (cool relay 1). However, I'm not sure with the remaining two wires. E (emergency heat) and O (cool active reversing valve) in MapleChase. I tried to put E into E (emergency heat relay), and O into W (also O/B for 1st stage heat relay or Changeover valve for heat pumps). But I got hot air instead of cool air, although the thermostat says cooling. This doesn't match any wiring guide in TH8320 user manual.

Please help. Thank you very much.

The "O" terminel needs to be wired to the same color wire as the old thermostat was. You will probably have to go into advanced setup to tell the thermostat that you have a heat pump, it will tell you how to do this in the installers guide. Mike

Thank you very much for your help. It looks it's working now. The problem was that I didn't change the advanced setup for System type to 7 for 2 heat/1 cool heat pump (with aux. heat). It was defaulting to 1 heat/1 cool conventional. I'm still not sure if the wirings are completely correct. I'll keep watching it. Thanks again.