Thermostats have multiple issues when you start checking them against thermometers.
1) the built-in thermometer may not match the set temperature because one or both need calibration. Compare the built-in to an external thermometer and see if there is any adjustment to make them match. Record the setting on the thermostat and the temperature when it starts and stops -- there should be a 1-3 degree range which may be adjustable. The set point should be in the middle of the on-off temperature spread. 2) the thermostat has a heat anticipator setting which may be set poorly -- turning off the heat before it reaches the set point - the fan normally runs for 1-2 minutes after the heat source is off. The anticipator is used to stop heating before reaching the set point as there are still a lot of BTUs coming out during the fan run-down -- usually 1-2 minutes.
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Thermostats have multiple issues when you start checking them against thermometers.
1) the built-in thermometer may not match the set temperature because one or both need calibration. Compare the built-in to an external thermometer and see if there is any adjustment to make them match. Record the setting on the thermostat and the temperature when it starts and stops -- there should be a 1-3 degree range which may be adjustable. The set point should be in the middle of the on-off temperature spread.
2) the thermostat has a heat anticipator setting which may be set poorly -- turning off the heat before it reaches the set point - the fan normally runs for 1-2 minutes after the heat source is off. The anticipator is used to stop heating before reaching the set point as there are still a lot of BTUs coming out during the fan run-down -- usually 1-2 minutes.