HVAC School - For Techs, By Techs
The History of the Thermostat - Short #267
· Summarized
Key takeaways
- The thermostat has been pivotal in shaping comfort and energy use, evolving from manual control to smart technology.
- Warren S. Johnson's invention of the pneumatic thermostat revolutionized temperature control.
- Thermostats have transitioned from mercury systems to digital devices, influencing the design of today's smart home technologies.
- Comfort is more than just temperature; humidity, air quality, and other factors also play critical roles.
- Responsibly recycling old thermostats is essential to prevent mercury pollution.
Summary
Introduction to the Thermostat's Impact
The podcast opens with an introduction to the thermostat's critical role in modern comfort and energy use. Brian humorously contrasts the podcast with the Black Eyed Peas before diving into the episode's core topic.
The Birth of Automatic Temperature Control
Before 1883, temperature control was rudimentary, often relying on manual labor. The introduction of the pneumatic thermostat by Warren S. Johnson marked a significant turning point in HVAC history, transitioning control from janitors to self-regulating systems.
Evolution of Thermostat Technology
The evolution from pneumatic to electrical systems in the 1920s and 30s heralded smaller, more efficient thermostats. Honeywell's T87 round thermostat, designed by Henry Dreyfuss, became an iconic representation of comfort in the home.
The Dark Side of Mercury Thermostats
While mercury thermostats were revolutionary, their environmental impact raised concerns. Listeners are urged to recycle these devices responsibly to mitigate mercury pollution.
The Digital Revolution and Future Outlook
The shift to digital thermostats led to the creation of smart devices, such as the Nest Learning Thermostat. However, true comfort involves factors beyond mere temperature, including humidity and air quality—areas where future thermostat design must improve.
Final Thoughts and Lessons Learned
Brian emphasizes the importance of respecting historical technology while highlighting the necessity of evolving comfort controls that encompass a broader understanding of human comfort and environmental impacts.
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Show notes
In this short podcast, Bryan gives another history lesson and goes over the history of the thermostat.
Before 1883, automatic temperature control simply did not exist; we shoveled fuel into the furnace and opened windows. If a room got too hot in a commercial building, the janitor would go downstairs to choke the draft damper; this person was responsible for manually controlling comfort.
Warren S. Johnson, a Milwaukee-based college professor, sought to do something about his classroom's sweltering heat. He created a pneumatic thermostat that mounted to the wall, sensed temperature, and used air pressure and mechanical systems to control dampers. This invention grew in popularity, and he founded Johnson Controls.
Compressed air ran entire HVAC networks by adjusting dampers and valves before electricity went mainstream. Engineers experimented with bi-metallic strips, which could open or close an electrical circuit based on temperature changes, which made thermostats smaller and cheaper. Honeywell came on the scene by hiring industrial designer Henry Dreyfuss, who invented the mercury thermostat: the T87 round thermostat. When the bimetal coil tilted, mercury rolled from one end to the other to complete or open the circuit. These thermostats had a heat anticipator, which kept them from overshooting the temperature. Unfortunately, when these thermostats were disposed of, the mercury polluted the environment and affected the central nervous system.
The digital thermostat came on the scene to replace the mercury thermostat, which led to the development of the Nest smart thermostat. However, all this time, comfort has been associated with the number on the thermostat; smart comfort controls that learn our routines and monitor dew point, relative humidity, and IAQ are the next step to create true comfort and health.
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