1902, willis carrier, an American, designed the first air conditioning system. 1906 applied for the American patent in the name of "air handling device". Carrier's invention originated in a printing workshop. Due to the change of air temperature and humidity, the printing machine makes the paper stretch, the oil colors are not arranged correctly, and the printed things are blurred. For this reason, Carrier has opened the door to the commercialization of air conditioners. In the next 20 years, Carrier's air conditioners were gradually used to adjust the temperature and humidity in the production process. And enter many industries, such as chemical, pharmaceutical, food, arms and other industries.

The development of household air conditioners began in the mid-1920s.

The first generation thermostat is mainly electrical products. The temperature sensor adopts bimetal or pneumatic temperature bag, and the temperature is set by adjusting the pre-tightening force through the "given temperature dial". Fan three-speed switch and season switch are mechanical switches. There are many problems in this kind of products, such as "the temperature setting division value is too thick", "the time constant is too large" and "the mechanical switch is easy to be damaged".

The second-generation thermostat is an electronic product, and the temperature sensor adopts thermistor or thermal resistor. The temperature setting and wind speed switch of some products realize the man-machine interaction interface by touching the key and LCD screen, the hot and cold switching is automatically completed, and the operational amplifier circuit and the switch circuit realize two-position adjustment. This kind of products improve the man-machine interface and solve the problems such as "the temperature setting division value is too thick", but there are still some problems such as "low control accuracy", "large time constant" and "complicated operation".

At present, domestic and foreign manufacturers are developing the third generation intelligent room temperature controller, and applying new control model and numerical control chip to realize intelligent control. At present, domestic manufacturers have produced intelligent room temperature controllers, which have been applied in practical projects.