The Engineer Who Invented Air Conditioning: Willis Carrier

Air conditioning was initially invented to improve the efficiency of paper manufacturing.
Trevor English

Air conditioning is an essential part of the 21st century. We pretty much couldn't live without the thermal space altering device. However, for most of human history, humans have lived without air conditioning. 

Homes used to be built with thicker walls that were much more resistant to exterior thermal changes. In large part, the invention of A/C changed home and infrastructure design.

However, in the late 1800s and early 1900s, after the strong development of the American Industrial Revolution had played out, factories started experiencing temperature-related problems, especially paper factories.

The birth of A/C

Sackett & Wilhelms Lithography and Printing Company were running into issues with their multi-color printing process. Varying humidity was causing the paper to expand and contract ever so slightly, causing deviations in layers of ink, resulting in excess scrap and waste. Humidity was the issue in their plant, and they needed help to solve it.

Sackett & Wilhelms approached consulting engineer Walter Timmis, who then contracted the services of J. Irvine Lyle, the head of a company called Buffalo Forge's New York office. Buffalo Forge was a supplier of forges, fans, and hot blast heaters—and they also employed brilliant engineers who designed custom solutions for clients.

One of those engineers was Willis Carrier.

Lyle tasked Carrier to design a system for Sackett & Wilhelms that would control humidity in their Brooklyn manufacturing plant in 1902.


Carrier went to work and eventually arrived at a solution that laid the foundation for modern air conditioning. He developed a system that replaced steam with cold water flowing through heating coils. This would ultimately balance the temperature on the surface of the coils, in turn, pulling a given air temperature down to the desired dew point. By controlling this temperature, and thus hitting the desired dew point, Carrier could literally pull moisture out of the air.

His design was first installed in the plant that summer along with a system of fans, heaters, ducts, and pipes to move air and control the temperature. Water was drawn in for the cooling system that was designed to maintain the humidity in the plant at 55% year round. In the summer, that meant the system had the equivalent cooling effect of melting over 100,000 pounds of ice each day. Carrier's invention had worked.

Carrier realized the potential this initial machine and invention had, so for the next five years, he continued to develop tools around the concept of controlling humidity and temperatures in factories and buildings.

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Complementing Carrier's initial coil designs, he also devised a counterintuitive method of drying air by passing it through a spray of water, using that spray to condense more water in the air. Soon after that idea, Carrier also realized that by heating that spray of water, he could control the air's dew point and thus guarantee a particular humidity in a building.

The Carrier air conditioning company

By 1907, Carrier had reached the upper echelons of management at Buffalo Forge. The company had successfully implemented its air conditioning equipment in factories across the world at this point, so they moved to create an air conditioning focused company: The Carrier Air Conditioning Company of America. The company was officially incorporated in 1909 and continued to grow in the following years.

The Engineer Who Invented Air Conditioning: Willis Carrier
Source: Wikimedia/Carrier

Carrier's work in the air conditioning field culminated in one of the most prolific documents ever crafted on the subject. Titled "Rational Psychrometric Formulae," Carrier presented the document to the American Society of Mechanical Engineers (ASME) in late 1911. His charts presented in this document were the first to accurately correlate temperature and humidity in the design of A/C systems.

A few more years went by, and Carrier was still leading the world in air conditioning technology. They sold machines to malt houses, candy factories, breweries, meat packaging facilities, shipbuilders, and food suppliers. The list went on forever. Carrier Air conditioning had become the leader in this new industry of air conditioning and the world was changed forever.

However, it was 1914, and WWI had just begun. Economies were in a tailspin, and Buffalo Forge called for the dissolution of Carrier Air Conditioning. Determined to press forward, Lyle and Carrier founded a new company, Carrier Engineering Corporation, in 1915.

This new company started landing contracts for cooling buildings left and right. In 1918 they brought A/C to the Atlas power company's substations resulting in a more stable power grid and a safer working environment. They helped cool ammunition plants crucial to the war effort. Air conditioning was changing the way modern manufacturing took place.

In May 1922, Carrier reinvented the A/C with the centrifugal refrigeration machine or chiller.

Chillers work to remove heat from liquid through a vapor compression cycle. This liquid containing the absorbed heat is then pumped through a heat exchanger to cool equipment or air. It's this system of using a refrigerant liquid, such as water, that is still present in modern A/C systems. This system also made A/C systems safer and meant that they would eventually be shrunk down to sizes that could accommodate domestic and smaller uses like homes and cars.

In 1924, this centrifugal system was mass rolled out into movie theaters across the US. For many at the time, these theaters became the places that people went to relax from the heat and cool off. Movie theaters became a place for comfort, a place to get together in large part because of Carriers A/C technology.

Growth continued, and in 1926, the 21-story Milam Building in San Antonio, Texas, became the first skyscraper air-conditioned from the basement to the roof during its construction. Air conditioning had proliferated into American society and was spreading across the world.

The rest of A/C development is history. Engineering of the machines changed, and more and more buildings across the world became cooled and heated using Carrier's machines. Today, you can pretty much cool anything and everything by using some form of Carrier's A/C machine. And that's the story of how Willis Carrier invented the A/C, founded a company, and went on to change the way that we interact with engineering across the world.

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