I currently live in NW Florida, in an open plan 1 story house with a vaulted ceiling. My thermostat is located in the middle of the large living room/kitchen area, which takes up the majority of the space under the vaulted ceiling. The bedrooms all have standard 8' ceilings and sit at the corners of the house. I'm wondering if there is a problem with my thermostat because no matter what temp I set it to, it manages to heat my house to the temp just below the temp I've programmed, but nothing more. For instance, if I set my temp to 68 degrees, the temp in the room (or at least by the thermostat) will reach 67 degrees after which my vents begin spewing "cool" air. If I set it to 69, it gets to 68 and does the same thing. This defeats the purpose of a thermostat, because I have a system which never shuts off since it never reads the set temp. I've even tried setting the thermostat to a temp already reached and it still continues to run. It's winter time and with temps outside as low as the mid 30's my house never gets warmer than 69 degrees no matter how long I run the system.

My system configuration is as follows: Large return on the ceiling about 7 feet directly above the thermostat. One 12x12x1 return on the bottom part of a wall in the master bedroom. Vents on ceilings throughout the house. One vent is just above the thermostat next to the return on the ceiling . Is my return sucking up all the heat coming from this vent? Is the ceiling a logical place for a large HVAC return? Am I an idiot for buying this house? Am I doing something wrong? Is it because I have tile floors in the kitchen and living room? The system is only 5 years old. Need some answers, please.