we have a honeywell programmable thermostat for a water-based heating
system.
it often gets much hotter in the house than I se the thermostat to, and I
always attributed this to the fact that the baseboard heaters are located at
the extremities of the house while the htermostat is in the middle of the
house, with no heater close to it.

today, however, I woke up to a temperature of 73 fahrenheit while the
thermostat is set at 71. I just saw the thermostat turningon the heating
system, even though the temp has been a constant 73 since this morning, it's
not too cold outside and the temp is still set at 71.

what on earth could possibly make this thermostat turn the heating on when
it's set at 71 and the temp reads 73?