When you set a thermostat to a specific temperature, such as 70 degrees Fahrenheit, its primary function is to maintain the temperature in the vicinity of the set point. The thermostat is equipped with sensors that detect the current temperature and compare it to the desired set point.
When the temperature nears the set point, the thermostat's control system will activate the appropriate heating or cooling equipment to either raise or lower the temperature accordingly. Once the temperature reaches the set point, the thermostat will typically turn off the heating or cooling system to prevent overshooting the desired temperature.
However, it's important to note that thermostats can have a small margin of error, usually within a degree or two, due to variations in sensor accuracy and the response time of the heating or cooling equipment. This margin is to avoid frequent cycling of the system and ensure a comfortable temperature range.
Additionally, some thermostats may have specific settings or features that allow you to customize the temperature differentials or other parameters related to the system's operation. Therefore, the exact behavior of a thermostat can depend on its specific model and settings.