Nov. 16, 1888: Early Johnson heat regulating system passes Prussian test

Although it was formed only three years earlier, word of the Johnson Electric Service Company (as Johnson Controls was then known) had begun to spread across the Atlantic. In fact, at the request of a Prussian government representative, a complete outfit of Johnson heat regulating apparatus was sent to the Royal Prussian Ministry of Public Works in Berlin. There, Ministry director Professor Hermann Rietschel began testing it on November 16, 1888.  

That day in Berlin was cold, with an early morning low of 37 degrees Fahrenheit (3 degrees Celsius) and a daytime high of only 45 degrees Fahrenheit (7 degrees Celsius). Yet the room temperature where the system was being tested maintained an even keel, fluctuating no more than one degree Fahrenheit (between 65.3 and 66.2 degrees Fahrenheit).

According to the performance report that followed a test trial of over 100 days, "The apparatus, during the entire test, did not fail a single time [italics in the report]. It always preserved the desired temperature in the room, and it required no special attention, ... ."