The concept of Air-Rotation® was invented and patented by Nelson Johnson, the founder of Johnson Heater Corporation in the 1950’s. Prior to this patent, Nelson also experimented with Air-Rotation with large floor furnaces designed for gravity heat distribution in the 1940’s. Nelson modified the furnaces to provide a single point of introducing heat into a large open space, and then modified the furnace to circulate the heat output with a ductless fan system. The early systems took the form of a brick mason building a firebrick heat chamber and various forms of indirect-fired metal shell and tube air-to-air heat exchangers. The early experimental data indicated the key to properly conditioning a large open space was the air circulation between a high discharge and a floor level return. Heat could be directed, or ducted into a large building by any number of heat producing devices; but if it was not evenly distributed, there would be hot and cold spots, stratification and wasted heating fuel that would fail to satisfy the thermostat control. Nelson gathered vast amounts of data and monitored the heating fuel used in actual buildings. To monitor fuel usage on a fair basis, he used the then newly developed “Degree Day Method”, a system pioneered by fuel oil distributors to predict when fuel oil deliveries would be needed by their customers. Nelson was able to show considerable fuel savings while providing other demonstrable benefits. The patent on the Air-Rotation® concept was merely the beginning. The application of the Air-Rotation® concept has been constantly refined by Nelson’s successors at Johnson Heater Corporation.

The early Air-Rotation® HVAC Systems in the 1950’s and 1960’s used a centrifugal blower to distribute the heat in the large open plan buildings. The early Air-Rotation® HVAC Systems were free standing, ductless floor mounted units and did not require the high static handling capability of centrifugal fans. Johnson engineers developed quiet, high-efficiency axial fans that could adequately move the air through the heating unit and provide the necessary air circulation in the conditioned building. By the mid 1970’s two horizontally mounted axial fans of 7-1/2 Hp. each were doing the job of a previous 40 Hp. centrifugal blower. This, however, was only the beginning!

Johnson engineers have made many improvements in the Air-Rotation HVAC Systems with current models incorporating the best available technology. Today’s Johnson Air-Rotation HVAC Systems have a wide variety of options and are able to heat, cool, circulate, dehumidify air or add humidity and do these things with incredible energy efficiency.

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