Penn Electric Switch Company Thermostat

Albert Penn of the Penn Electric Switch Company in Des Moines, Iowa invented this Type AA thermostat in 1928. His invention was given patent number 1,749,392 on March 4, 1930 and describes a room thermostat in which a switch is controlled by a temperature actuated bellows element to close or break a circuit that would turn on the furnace. While this design was innovative, it was not as sensitive to temperature changes as other thermostats, and the large bellows element would have jutted 4 inches out from the wall. Other thermostats were becoming smaller and more attractive, and Penn soon changed its design seen in object 2008.0011.12. While similarly styled, the thermostatic metal in the Type B worked better than the bellows, and the device protruded a mere 1.5 inches from the wall.
The ubiquity of thermostats in 21st century homes shrouds the decades of innovation, industrial design, and engineering that went into making them an everyday object in almost every home. In the early 20th century, a majority of American households still heated their homes with manually operated furnaces that required a trip down to the basement and stoking the coal fired furnace. Albert Butz’s “damper-flapper” system was patented in 1886 and allowed home owner to set the thermostat to a certain temperature which would open a damper to the furnace, increasing the fire and heating the house. Progressive innovations allowed for the thermostats to use gas lines, incorporate electricity, turn on at a set time, include heating and cooling in one mechanism, and even connect to the internet.
overall: 6 3/4 in x 3 1/4 in x 4 in; 17.145 cm x 8.255 cm x 10.16 cm
ID Number
accession number
catalog number
See more items in
Work and Industry: Mechanical and Civil Engineering
Domestic Furnishings
Engineering, Building, and Architecture
Object Project
Exhibition Location
National Museum of American History
Data Source
National Museum of American History


Add a comment about this object