Wiring a Honeywell RTH7500

I am not familiar with that honeywell number. Maybe iot is a consumer model. I am familiar with trol a temp and it is a forced air zoning control. if the thermostat you have doesn't power the O constantly in the cool mode it will not work.

I am trying to install 2 Honeywell RTH7500 programmable thermostats to control 2 (out of three) separate zones (1st floor & 2nd floor) within my house.

The old thermostat (TrolAtemp) on the 1st floor had 6 wires, R, W, Y, G, B and O (tan line). The RTH7500 does not have a connection for "O" for a Conventional (non Heat pump) systems.

After installing the 1st floor, everything worked fine on the 1st floor but after installing the 2nd floor we found that the 2nd floor thermostat no longer worked. Also, the thermostat in the basement (not replaced) stopped working.

I think the "O" controls the other 2 zones (the total system can be turned on/off only from the 1st floor) but the RTH7500 installation guide doesn't say what to do.

Can anyone help? Honeywell support is only open M-F 8-5