Minneapolis-Honeywell TM850 Chronotherm Thermostat

The Minneapolis-Honeywell Regulator Company of Minneapolis, Minnesota manufactured this Honeywell Comfort TM850 Chronotherm thermostat during the 1950s. The Honeywell Chronotherm brand has been manufactured in different models since 1935. While conventional thermostats allowed for different settings during the day and night, most had to be manually changed by hand. The Chronotherm automatically changed those settings so that the temperature could be lowered at night and then turned up each morning. The TM850 Chronotherm featured a Telechron clock and sold for $34.90 in 1950.
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.
Currently not on view
Object Name
date made
ca 1950
Honeywell Inc.
overall: 4 3/4 in x 2 5/8 in x 2 7/8 in; 12.065 cm x 6.6675 cm x 7.3025 cm
ID Number
accession number
catalog number
Domestic Furnishings
Engineering, Building, and Architecture
See more items in
Work and Industry: Mechanical and Civil Engineering
Data Source
National Museum of American History, Kenneth E. Behring Center

Visitor Comments

3/21/2015 3:47:39 PM
Charles Grace
What is the purpose of the integral heater with this thermostat? Some sort of compensation? The steel around the clock motor is running, maybe 130-140 Deg after stabilizing. Can't keep my fingers on it. The Bi-metal strip/ contact area is considerably cooler, but must get radiated heat from the motor area. Is all of this normal?? It runs fine and the clock is quiet and keeps good time. Synchronous motor I guess. Thanx for any input. Charlie
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