60 Fun Facts About HVAC

In 1902 Willis Carrier designed the first modern air-conditioning system for a Brooklyn firm. What did that firm do?

Summer humidity was making the paper swell and the colour inks misalign, so the system was built to control moisture rather than to make anyone comfortable.

Willis Carrier was a research engineer at which firm when he designed that first system?

Carrier had just finished a master's in engineering at Cornell in 1901; the firm's founders later backed him when he struck out on his own.

Who coined 'air conditioning' in a 1906 patent claim while trying to humidify his North Carolina textile mill?

Textile mills were early adopters because the right humidity keeps yarn from snapping, and Carrier happily borrowed the phrase for his own company.

Willis Carrier was granted U.S. patent 808,897 on January 2, 1906. What was the invention titled?

The 'treatment' was spraying air with water to add or remove humidity, which is why early systems were essentially very fancy air washers.

How many young engineers pooled $32,600 in 1915 to found the Carrier Engineering Corporation?

The company later merged with two rivals in 1930 to become the Carrier Corporation and moved to Syracuse, New York, in 1937.

What did Willis Carrier unveil in May 1922, described as his most influential innovation?

Its first big commercial job was three 195-ton units for the J.L. Hudson department store in Detroit in 1924.

In which city did Carrier's 1920s cooling system for the 2,400-seat Rivoli Theatre make headlines?

The Rivoli had opened in 1917 under showman Samuel 'Roxy' Rothafel, and 'cool inside' summer movies became a staple of theatre marketing.

Which automaker was the first to offer an air-conditioning unit in its cars, in 1939?

The unit filled much of the trunk and had no dashboard control; to switch it off you had to stop and remove the compressor belt.

In 1931 H.H. Schultz and J.Q. Sherman developed the most common type of which appliance?

Their unit sat on a window ledge; early models cost between $10,000 and $50,000, several times the price of a house at the time.

What was the profession of John Gorrie, who patented an ice-making machine in 1851 to cool sickrooms?

He died broke and forgotten in 1855, but Florida later placed his statue in the National Statuary Hall of the U.S. Capitol.

James Harrison built the first mechanical ice machine in Geelong in 1851. Which country is Geelong in?

Harrison was a newspaper printer who noticed ether chilled metal type as it evaporated, then scaled the effect up for breweries and meat packers.

Refrigeration pioneer Frederick McKinley Jones co-founded which company with Joseph Numero?

During the Second World War his units kept blood, medicine and food cold for army hospitals and battlefields; he earned 61 patents in all.

In 1991 Frederick McKinley Jones posthumously became the first African American to receive which honour?

Industry colleagues had nicknamed him the 'King of Cool', and he was inducted into the National Inventors Hall of Fame in 2007.

In which refrigeration component does liquid refrigerant boil and absorb heat from indoor air?

Because that coil runs cold enough for moisture in the air to condense on it, an air conditioner also works as a dehumidifier.

Which refrigeration-cycle component is also known as the metering device?

It creates the pressure drop that lets the refrigerant flash into a cold, low-pressure mist just before it enters the indoor coil.

Frigidaire, where Freon was synthesized in the late 1920s, was then a division of which company?

The team was hunting for a non-toxic, non-flammable replacement for the ammonia, sulfur dioxide and methyl chloride that made early fridges dangerous.

Which inventor did J.R. McNeill say 'had more adverse impact on the atmosphere than any other single organism'?

He also developed leaded gasoline, and in 1924 he inhaled its vapour for a minute at a press conference to prove it was safe.

Which agreement, signed in 1987, became the first universally ratified treaty in United Nations history?

Kofi Annan called it 'perhaps the single most successful international agreement to date', and 16 September is now World Ozone Day.

The 2016 Kigali Amendment to the ozone treaty requires cutting which class of refrigerants by at least 85 percent?

These replacements do not harm ozone but are potent greenhouse gases, so the ozone treaty was repurposed as a climate treaty.

Which two chemists predicted in 1974 that CFCs would deplete the ozone layer?

The pair shared the 1995 Nobel Prize in Chemistry with Paul Crutzen for the work, which the chemical industry attacked for over a decade.

When R-22 was restricted in the 2010s, most new US home ACs shifted to which refrigerant?

Sold under trade names such as Puron, it runs at much higher pressures than its predecessor, so the two cannot be swapped in the same equipment; from 2025 it is itself giving way to R-454B and R-32.

Which hydrocarbon refrigerant was in over 70 percent of new EU household refrigerators by 2022?

Coded R-600a, it is flammable but so little is needed in a fridge that the charge is roughly a cigarette lighter's worth.

A 'ton' of cooling capacity is defined as how many BTU per hour?

That is about 3.5 kilowatts; a typical house needs one to five tons, and the unit was set as an industry standard back in 1903.

A ton of refrigeration was originally the heat to melt one short ton of ice over what period?

The unit dates from the 1880s ice trade, giving buyers a familiar yardstick when mechanical plants began replacing harvested lake ice.

A British thermal unit is the heat needed to raise how much water by one degree Fahrenheit?

It works out to about 1,055 joules, and U.S. natural gas is still priced per million BTU.

US residential air conditioners made after 2005 must have a minimum SEER rating of what?

The rating divides a season's cooling output in BTU by the electricity used in watt-hours; from 2023 a revised SEER2 test with regional minimums took over.

In the furnace efficiency rating AFUE, what does the letter A stand for?

A 90 percent unit delivers 90 BTU of heat for every 100 BTU of gas it burns; standard furnaces sit around 78 to 84 percent.

High-efficiency condensing furnaces are vented with PVC pipe rather than metal to prevent what?

A secondary heat exchanger pulls so much heat from the exhaust that water vapour condenses out, and that condensate is acidic.

Which component lets a heat pump switch between heating a home in winter and cooling it in summer?

Most air-source units lose efficiency below about 4 °C, though newer cold-climate models keep heating effectively down to −26 °C.

Who developed and built the first heat pump, in the 1850s?

The Austrian engineer used it to concentrate brine at a salt works, only a few years after Lord Kelvin had described the theory in 1852.

Which London venue opened in 1951 with a reversible water-source heat pump fed by the River Thames?

The gas-powered system was a showpiece of the Festival of Britain, decades before heat pumps became a mainstream heating option.

The first commercial ground-source heat pump was installed in 1948 in the Commonwealth Building in which US city?

The installation is now an ASME National Historic Mechanical Engineering Landmark, and the EPA has called such systems the most energy-efficient available.

Warren S. Johnson patented a bimetal thermostat in 1883 and founded a controls company. Which state was he from?

Johnson was a college professor annoyed that janitors kept interrupting his classes to check the room temperature.

Which industrial designer styled Honeywell's round T87 thermostat, first made in 1953?

The concept came from Honeywell engineer Carl Kronmiller; the round shape was meant to fix the crooked look of rectangular thermostats hung on walls.

Nest Labs founders Tony Fadell and Matt Rogers were both former engineers at which company?

Google bought the company in January 2014 for $3.2 billion in cash, completing the deal the day after announcing it.

A Roman hypocaust heated a room by circulating hot air from a furnace where?

It burned so much wood and needed such constant tending that only large villas and public baths could afford one.

Which improved version of Franklin's 1742 "Pennsylvania fireplace" later fixed its poor draft?

Franklin refused to patent the stove, writing that since we enjoy the inventions of others we should serve others freely with our own; Rittenhouse still lost the naming rights.

Businessman Franz San Galli invented the heating radiator in 1855 while living in which city?

Prussian-born, he called it a 'hot box', and Russian winters proved an ideal test market for the cast-iron design.

What does the air-filter rating MERV stand for?

The scale, created by ASHRAE in 1987, tests how well a filter catches particles between 0.3 and 10 micrometres across.

The standard MERV filter scale runs from 1 up to what top value?

The top-rated filters catch more than 95 percent of particles across the whole test range, while U.S. building codes only require MERV 6 in homes.

ASHRAE began in what year as the American Society of Heating and Ventilating Engineers?

It merged with the American Society of Refrigerating Engineers in 1959 to get its current name and had more than 50,000 members by the 2020s.

The 1976 outbreak that named Legionnaires' disease struck which Philadelphia hotel?

The bacterium was found breeding in the hotel's air-conditioning cooling tower; 182 people fell ill and 29 died before it was identified in January 1977.

Engineers from which country patented the hyperboloid cooling tower shape in 1916?

The first reinforced-concrete version went up at the Dutch State Mine Emma in 1917; the tallest today is about 210 metres in Huaibei, China.

Evaporative 'swamp' coolers are most effective in which kind of climate?

The cooling comes from water absorbing heat as it evaporates, so the drier the air, the bigger the temperature drop, at the cost of adding humidity.

Which company sold the first wall-mounted mini-split air conditioner in Japan in 1968?

It was also the first air conditioner with a cross-flow fan; ductless mini-splits reached the U.S. market the following year.

Which company invented variable refrigerant flow (VRF) technology in 1982?

It trademarked the name VRV, and heat-recovery versions can warm some rooms with the heat pulled out of others at the same time.

Which state prohibited duct tape for ductwork after a 1998 Berkeley lab study found it fails on heating ducts?

The tape began life as waterproof 'duck tape' for sealing WWII ammunition boxes; foil tape and mastic are what technicians actually use on ducts.

What is the term for the temperature at which water vapour in the air begins to condense into liquid?

Willis Carrier plotted these relationships on the first psychrometric chart in 1904, still the working diagram of HVAC engineers.

Under EPA Section 608, a Type I technician certification covers servicing which equipment?

Type II covers high-pressure and Type III low-pressure equipment; passing all three earns a Universal card.

Roughly what share of global electricity did air conditioning consume in 2022?

That was enough to account for 3 percent of greenhouse gas emissions, with an estimated 1.6 billion units in use worldwide as of 2016.

Airtemp, a Detroit automaker's climate-control brand, made its first installation in 1930 in which skyscraper?

Airtemp supplied medical refrigeration units in the Second World War and dominated the 1940s before being sold to Fedders in 1976.

Most modern home thermostats run on low-voltage control circuits of roughly how many volts AC?

The mechanical types inside use a bimetallic strip, and some models add an 'anticipator' that cuts the burner just before the setpoint is reached.

Robert C. Webber built the first ground-source heat pump in the 1940s after experimenting with which appliance?

He noticed the unit's outlet pipe ran hot, and ended up heating his house with copper coils buried in the ground.

What is it called when warm air escapes through high openings and pulls cool air in through low ones?

Cross ventilation is the other big natural strategy, relying on wind pressure differences on opposite sides of a building.

A room is under positive pressure when what is true of its airflow?

Positive pressure is used to keep outside contaminants from seeping in; negative pressure does the reverse for isolation rooms.

What is the term for heating systems that use water as the heat-transfer medium?

Modern hot-water boilers use a circulator pump rather than gravity, and the same water can feed a heat exchanger for bathing water.

At six air changes per hour, a room's full volume of air is replaced roughly how often?

Four air changes per hour is typical for comfort, while a warehouse might manage with two.

In 2023 the CDC set what minimum air changes per hour as a target for all spaces?

Natural ventilation through open doors and windows helps cut the spread of airborne illnesses like flu and COVID-19.

Alfred Wolff designed the first comfort air-conditioning system in 1902 for which building?

The same year Willis Carrier fitted a Brooklyn printing company with a process air-conditioning unit.

In which year did Coyne College become the first school to offer HVAC training?

The first residential air conditioning was installed by 1914, and residential AC became widespread in the 1950s.