Residential HVAC Installation Practice Exam

A mechanical thermostat utilizes a mercury switch to regulate temperature. This type of thermostat operates based on the physical movement of mercury in a glass vial that responds to temperature changes. When the temperature rises or falls past a certain point, the mercury tilts and completes an electrical circuit, turning the heating or cooling system on or off.

Mechanical thermostats are typically simpler and have been used for many decades. They do not rely on digital components, but rather on mechanical parts that can lead to a slower response time in temperature regulation compared to modern alternatives. The accuracy of a mercury switch can be affected by factors such as position and potential vibration, but it is a straightforward and reliable mechanism for temperature control in a variety of HVAC applications.

The other types of thermostats mentioned, such as digital, programmable, and smart thermostats, operate using electronic sensors and controls, which provide different functionalities and capabilities compared to mechanical thermostats with a mercury switch.