Who invented the thermostat?
Thermostat
Warren S. Johnson (1847–1911) of Wisconsin patented a bi-metal room thermostat in 1883, and two years later filed a patent for the first multi-zone thermostatic control system.
Albert Butz (1849–1905) invented the electric thermostat and patented it in 1886.
Wax thermostatic element
The first thermostats used a sealed capsule of an organic liquid with a boiling point just below the desired opening temperature. These capsules were made in the form of a cylindrical bellows. As the liquid boiled inside the capsule, the capsule bellows expanded, opening a sheet brass plug valve within the thermostat. As these thermostats could fail in service, they were designed for easy replacement during servicing, usually by being mounted under the water outlet fitting at the top of the cylinder block. Conveniently this was also the hottest accessible part of the cooling circuit, giving a fast response when warming up.