Trying to figure out how to wire the T3000 correctly. Here’s a picture of the old Honeywell thermostat my first attempt resulted in the heat kicking on when I selected “cool”
I believe the orange wire going into w1 on old stat needs to go to the o/b terminal. The white wire going into w2 on old stat would go into w1 on the new stat.
That model of Honeywell thermostat causes a lot of confusion for users when rewiring due to how its terminals are double labeled. You need to know if you are using a conventional HVAC or a Heat Pump. I am guessing you have a Heat Pump and used the conventional labels. That is typically what causes issues.
If that is the case, the above post is correct, that Orange is the changeover wire and should go into O. The white wire is the heat stage, into W1