I was going to bet that it was a round Honeywell electrical thermostat. The answer is pretty simple. Read the instructions. Number 1, the unit has to be installed level. Number 2, there is an adjustment screw that controls the sensativity of the unit. As I recall, it requires a VOM to set it exactly but you can get it close without one. Actually, these work pretty well if you install and adjust them correctly. They were the standard for a lot of years. If you are in a new house, you might ask the contractor to have the HVAC contractor to come out and adjust it.