Free Sample
The Complete Handbook of Thermostats
For HVAC Professionals, Facility Managers, and System Builders
by Alumigogo Books
Chapter 1: Understanding Thermostats
A thermostat is fundamentally a device that measures temperature and makes a switching decision: when the measured temperature crosses a boundary you set, the thermostat either turns a heating or cooling system on or off. That is its core job. Everything else—displays, schedules, wireless communication, user interfaces—is either a way to set those boundaries or a way to observe what the thermostat is doing.
To understand why this matters, consider a typical residential heating scenario. On a winter morning, the air temperature inside your home is 62°F. You want it to be 70°F. You set your thermostat setpoint to 70°F. The thermostat's temperature sensor continuously reads the current temperature. When it detects that the actual temperature is below 70°F, it closes an electrical switch that energizes your furnace. The furnace burns fuel and moves warm air through your home. After a while, the temperature rises past 70°F. The thermostat detects this change, opens the switch, and the furnace shuts off. The temperature slowly drifts down, and when it falls below 70°F again, the cycle repeats. This on-and-off cycle is what keeps your home near your desired temperature.
This simple feedback loop happens thousands of times a year in most buildings. The thermostat is the link between human comfort preference and machine behavior. Without a thermostat, you would need to manually start and stop your furnace dozens of times a day. With one, the building maintains itself within a narrow temperature band automatically.
The practical importance of