HVAC – Classroom Focus and the Thermostat

Think back to your time in grade school. Not all classrooms were created equal. Some felt like the inside of a refrigerator while others could be stifling hot. It is hard to concentrate on reading, writing, and ‘rithmatic when your teeth are chattering. 

This was School Superintendent Warren Johnson’s concern as he observed the classrooms in Dunn County, Wisconsin. In the late 1800’s, classroom instruction was interrupted hourly by janitors checking thermostats in each room. The janitors would then return to the furnace room where they would open or close dampers connected to a furnace, controlling the release of hot air into each classroom. It would cost valuable class instruction time to regain the students’ attention. To decrease these interruptions and streamline the process of adjusting the heat, Johnson displayed true American ingenuity and decided to solve the problem.  

Patented as the Johnson System of Temperature Regulation in 1883, the “electric tele-thermoscope” was installed in each classroom or “zone.” A fused brass and steel element inside the device was designed to change its shape in response to temperature changes in that zone. The other end of the element was attached to a valve or damper which controlled the release of steam or hot water into the zone’s air vents. As the metal element would expand or contract, the valves or dampers would open or close, keeping the classroom temperature steady and enabling staff to set the temperature to suit their needs.

Today’s thermostats, like KMC’s FlexStat, are also wall mounted and temperature-sensing. But unlike their original predecessors, FlexStat is available with multiple configurations of inputs and outputs, as well as built-in or custom programming, to ensure that a variety of application needs can be met. Temperature sensing is standard, with sensing options available for humidity, CO2, and motion.  

Warren Johnson’s legacy of American ingenuity lives on at KMC, where our American-made products are giving today’s classrooms, homes, and businesses greater temperature control than ever before. 

Join us next time as we explore the life of an immigrant searching for the American dream amid a brutal war and his invention that we still use today.  

For more information on this and other KMC Controls products, please visit https://www.kmccontrols.com/, your one-stop turnkey solution for building control. We specialize in open, secure, and scalable building automations, teaming up with leading technology providers to create innovative products that help customers increase operating efficiency, optimize energy usage, maximize comfort, and improve safety. Let our Building Geniuses® take your facility to the next level.


American Society of Mechanical Engineers 

Electric Tele-Thermoscope

1800’s Classroom

Warren Johnson