Inconsistent thermostat

I’d appreciate someone explaining “Differential Temp.” I understand it to be the overall “range” of temps the thermostat will allow above and below the set temp. In other words, if I have the temp set for 68 degrees for heating (I don’t need cooling), and the differential is 3 degrees, once the temperature reaches 65 degrees, the thermostat will turn on the furnace. Once the temperature reaches 71 degrees the thermostat will turn the furnace off.

If I have that right (or if the temp differential is only 1.5 degrees above and below) I really don’t know what goes on with my thermostat. It seems to turn the furnace on when the temp is what the thermostat is set for and runs for just a short period of time. Or, it actually starts the furnace when the temperature is above the set value and runs for a short period of time. The only time the thermostat acts as expected is when the time goes from ‘sleep’ to ‘home.’ The difference between the set values is 5 degrees, and the thermostat takes hardly any time at all getting from the ‘sleep’ temp to the ‘home’ temp. As I would expect.

If I’m mistaken in my description of the “Differential Temp”, I’d really like to see what the explanation is. And, if I’m correct in my description, I’d really like to have an explanation of what my thermostat is doing, since it surely doesn’t fit what “Differential Temp” is.

I’m particularly interested since the price of natural gas is so high right now. I feel like I’m being robbed by my thermostat.