I installed a honeywell RTH 221 but have found that with my system I get only hot air when on the cold setting and equally hot air on the heat setting. I need a suggestion on what to buy. The system is a Lenox installed when built in 1996. I have been informed by a member here that I bought the wrong thermostat and the wire connected to the O terminal was important! Even though the insallation manual said that some wires may not need be connected with newer thermostat and there was no terminal for the O or the C1 ( I beleive) it was a blue wire. Thank you all!