Electric thermostat
This early electric thermostat devised by Warren S. Johnson rang a bell in the plant room of a school so that the janitor could manually control the flow of warm air to that area.
Even the cave man who rubbed two sticks together knew that he needed some control over his fire. He got fed up lugging logs from the forest just for his missus to fling the goatskin door open to cool down! Fire was therefore rationed to conserve energy, which is pretty much what a thermostat now does. Without control, we squander precious resources or use our fabulous machines to exhaustion. Several millennia on the situation is hardly any different — but, thanks to Warren S. Johnson and his electric thermostat, we have a more choice in how we can remain comfortable in an economic way. Sadly, as so often is the case, it was the British who invented the thermostat but failed to sell the brilliance and commercial potential of the idea to a sceptical UK industry. In the 1940s a president of the IHVE (now CIBSE) ‘deprecated in his own practice the elaboration of automatic mechanisms, because in his view, they were not needed, and, in the second place, they were liable to get out of order’. Born in Vermont, Johnson worked as a printer, superintendent of schools and a surveyor of the Plains. In 1876 he was appointed Professor at the State Normal School in Whitewater where he experimented with control of the school’s warm-air heating system. Hand-operated dampers in the furnace room controlled the temperature of air supplied to the various classrooms. The janitor regularly toured the classrooms, noting the room temperature, then returned to the furnace to adjust the settings. In a wheeze very much like an ‘Upstairs, downstairs’ servant call system, Johnson installed electric thermostats in each room, connecting them to annunciators so that thermostat contacts rang an alarm bell and operated an indicator in the furnace room to show ‘warm’ or ‘cold’, leaving the janitor to adjust the dampers as required. Johnson was granted a patent for his electric tele-thermoscope. He went on to develop his well-known system of pneumatic controls. In 1885 he founded the Johnson Electric Service Company, which became a major international controls manufacturer. This in turn was a significant driving force in the eventual world-wide acceptance of automatic controls in the building services engineering industry.
