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Pioneers of refrigeration

The modern world is impossible to imagine without refrigeration. The Internet, food transportation, medical imaging, and vaccine research, such as COVID-19, relies on refrigeration to function. Even the sprawl of cities across the American south in the 1950s was inconceivable without refrigeration and air conditioning. So if you like vacationing in Vegas or taking the family to Disney World, you have refrigeration to thanks.  The history of refrigeration in many ways mirrors the history of America. 

For people who live in warmer climates, refrigeration is considered a life-or-death matter. It’s perhaps poetic, therefore, that among the first uses of refrigeration in America occurred after the assassination of President James A. Garfield. Four months into his first term, Garfield was fatally shot by Charles Guiteau, a madman who despised Garfield for failing to grant him a position in his cabinet

Guiteau shot the President with a revolver at the Baltimore and Potomac Railroad Station on July 2, 1881. Garfield was seriously injured and carried back to the White House, where naval engineers quickly rigged a rudimentary air cooling system using millions of pounds of ice and legions of fans to circulate the cooler air around the weakening president. While the hypothesis behind this treatment, that cooler temperatures decrease infection and contagion, was valid, the President still died 79 days later on September 19, 1881.

The principles informing the decision of Garfield’s doctors, and furthermore the development of modern refrigeration, originated in the work of a humble physician in a little-known hamlet on Florida’s Gulf Coast, Apalachicola. Born on the island of Nevis in 1802 and completing his medical education in New York, John Gorrie moved to Apalachicola because of his passion for treating tropical diseases. While modern science has discovered mosquito-borne bacteria to cause malaria, through the first part of the 19th century the disease was blamed on climate, hence the term “malaria,” Italian for “bad air.” 

Gorrie foresaw the beneficial impact cooler temperatures would have on his patients and invented what he called an “ice machine” by stacking bricks of ice ordered in a basin suspended from the hospital ceiling. This represents an open system of refrigeration as opposed to closed. Unfortunately, the medical community didn’t support his efforts and he died, humiliated, bankrupt, and alone, in 1855. Later recognized for his prescient efforts in modern refrigeration, he was memorialized by Florida in 1914 when sculptor C.A. Pillars created a monument of him located in the National Statuary Hall Collection.

Monument of John Gorrie

Monument of John Gorrie erected in 1914.

Like many American inventors, Gorrie’s work was anticipated by Benjamin Franklin, who discovered that evaporation of alcohol could freeze water, an insight that led to the synthesis of Freon in 1926. Renowned scientists such as William Cullen, Robert Faraday, and Jacob Perkins also contributed to the development of refrigeration and air conditioning, with Perkins, who patented the first “air conditioner” in 1835, celebrated as the “father of the air conditioner.” 

The twentieth century witnessed the transformation of refrigeration and air conditioning experiments from an area of scientific research to a money-making endeavor. In 1902, Willis Carrier of the Buffalo Forge company constructed an “air conditioner”  using cold groundwater, not compression, and began to sell it on the open market a bit later once the amazing comfort ramifications became clear. By the 1950s, air conditioning and refrigeration were a staple of American life, introducing pivotal changes in the way food was preserved, computer servers were cooled, and even playing a role in the creation of “galactic cities” in hotter climates, such as Houston, Las Vegas, Phoenix, Tampa, and Los Angeles. Today refrigeration and air conditioning are central to protocols in quantum mechanics, computer science, the Internet, space exploration, and vaccine development, in addition to our good old domestic air conditioners and refrigerators. Consider this: without refrigeration, you wouldn’t have had any beer to drink during quarantine.

Core principles of modern refrigeration

It’s amazing to think that the principles behind our every day refrigeration and air conditioning practice were there, in utero, hundreds of years ago in the minds of Ben Franklin, John Gorrie, and President Garfield’s doctors. The first and most important of these is the distinction between open and closed refrigeration and the related issue of compression refrigeration and alternate forms of refrigeration. 

Compression refrigeration

Compression refrigeration (also known as “closed-cycle compression refrigeration” and “vapor-compression refrigeration”) is the most common form of refrigeration in modern times. 

Compression refrigeration is an entirely mechanical process. Whereas some open systems exploit flow of air or wind, compression uses piping and circulation of a refrigerant through component parts. This type of refrigeration consists of a compressor, a condenser, a metering device, and an evaporator. Their purpose is to regulate the flow of the refrigerant, changing phase states to create energy. Each component has its own role to play:

  • Compressor: A pump that moves the refrigerant throughout the system by putting pressure on the gas. As the gas is compressed, its temperature increases. 
  • Condenser: A coil that receives gas (or vapor) from the compressor and removes heat from it to some other medium (often air), thus affecting a phase event change from gas to liquid. 
  • Metering Device/Expansion Device: This device can take a number of shapes, including a 1) thermostatic expansion valve; 2) capillary tubes; 3) fixed orifice pistons; and 4) a range of other non-conventional metering devices uses in specialties, for instance, floats or distributors. Regardless of the specific device modality, the purpose is to measure and respond to the refrigerant temperature as it exits the condenser and prepares to efficiently enter the evaporator. 
  • Evaporator: The evaporator is where the actual cooling effect occurs. It accomplishes this by transferring heat from the substance to be cooled (beer, vaccine cultures, computers) to the refrigerant, thus removing heat from the substance. After a phase change, the refrigerant leaves the evaporator in a vapor state to be pressurized again cyclically by the compressor. 

Refrigeration and air conditioning

While refrigeration and air conditioning are related, there are important functions and applications that separate one from the other. Refrigeration denotes the transfer of heat from an undesirable location to a desirable one. Heat always transfers from warm to cold. This means, importantly, that refrigeration consists, not of adding cold to a substance, but of removing heat from it. When you place a lukewarm beer in the refrigerator, you are putting that into a location where heat will be removed from it, thus cooling it. 

Air conditioning refers to the continuous process of regulating temperature, humidity, ventilation, and filtration. Its goal is to increase comfort by moving hot air from inside to outside, thus cooling the inside. In addition to increasing environmental comforts, air conditioning also makes the air safer to breathe and reduces humidity levels to prevent the development of mold and spores in the home. The invention of air conditioning, derived from the concept of refrigeration, was essential to the thriving of southern cities like Houston, New Orleans, and Miami. 

Contemporary applications of refrigeration

Infographic showing the environmental effect of CFCs.

Refrigeration is central to many of the most critical industries and technologies in the 21st century. You wouldn’t be reading this article if data servers weren’t kept cool by computer room air conditioning units (CRACs). In the medical field, imaging technologies, vaccine cultures, and organ transplants would be impossible without refrigeration. Potentially lethal food-borne illnesses such as staphylococcus aureus, botulism, e.coli, and trichinosis have almost been eradicated due to food safety and preservation techniques allowed by refrigeration. Even the Cold War.. if unintentionally,  owes its nickname to the refrigeration required for Kennedy’s New Society, where missiles, space travel, and nuclear storage required the temperature and energy stability provided by refrigeration. 


Since the early 19th century, refrigeration has developed from a scientist’s toy to a moneymaker’s dream to a technological necessity. However, in recent decades climatologists have discovered convincing correlations between the use of certain cooling procedures and refrigerants (CFSs, HCFCS) and climate change. As a result, modern refrigeration companies have began researching solid-state and magnetic-based technologies to reduce environmental impact. Overall, these systems harken back to the more “open” systems pioneered by Gorrie and Carrier, as well as Einstein’s pipe dream of “green” refrigeration and air conditioning.  Modern refrigeration experts encourage us to look back to look forward.

In HVAC and refrigeration the past is interesting and complex and the future is bright.

When you are checking a unit of any kind you should be keeping your eyes open for signs of arcing and melting at all of your wire connections and contact points. We find issues with melting terminals on contactors and in disconnects regularly, but rarely do we think about the relationship between circuit ampacity and wire size and the connections to our equipment.

First, consider the fact that a #10 wire doesn’t always have an ampacity of 30 amps, it has an ampacity of 30 amps with a 60° Celsius rated assembly at 30° Celsius ambient.

Now, look carefully at the wire and the contactor at the start of the article.

The wire (conductor) is rated at 90° and the contactor is rated at 75° when torqued down to 22 in/lbs on screw type terminals and 40 in/lbs on lug type.

So the entire assembly is only as good as the weakest link and the weakest link is the terminals and the terminals are only as good as the contact they are making.

Conclusion: The termination (connection) points are usually the weakest point of the circuit

When sizing conductors don’t forget ANY of the termination points. From the breaker to the disconnect to the unit, every termination point should be properly connected and the rating checked if you intend to use any ampacity other than 60° Celsius.

Check those connections. make sure they are snug and that they are properly suited for the ampacity of the circuit.

For more great info on this go HERE

— Bryan

This article was written by Senior Refrigeration tech Jeremy Smith. Big thanks to Jeremy for his contributions to HVAC School and the tech community.

Having spent many years in the trade and many years reading posts from techs on forums and social media, a big issue that I see is that troubleshooting is something of a lost art.

Troubleshooting is where the rubber meets the road for a service technician. Nobody cares what certifications you have, what union you belong to or anything else. If you can’t find the problem and solve it in a timely fashion, your customer and employer are not going to be happy.

One of the things that I think most guys struggle with is the mental aspect of troubleshooting. I’ll relate this in the form of a recent call I was sent on to “clean up”. It was a no heat call in a small convenience store. Trane RTU on a zone sensor.

The tech called me and related that the unit had a call for heat at the unit but the ignition sequence didn’t start. We talked a little about the problem, he checked some limits and a few other things. He wound up ordering an Ignition board and limit sensors. These were replaced late that night and the unit still didn’t work.
I was sent the next morning. Now, we get into the mental part of troubleshooting.

I met the tech so that he could communicate the basics of what he did. We talked for about 10 minutes and he went on to his job and I went to have a chat with the trouble unit.

20 minutes later, I had the problem solved. I found a failed RTRM board. Now, you guys that do Trane all the time probably aren’t surprised, but let’s analyze what went wrong and how this could have been handled on a “one stop” basis.

What did I do that the first Tech didn’t?

For starters, I took everything that I was told about the unit, what it was and wasn’t doing and what everybody and their brother thought was wrong with it and I threw it all out. Put it in a box in my head, closed the lid and locked it.

I dug out the basic Trane “Service Facts” book and started the troubleshooting procedure from Step 1 and followed it to the end.

Now, I can make these arrogant claims about how I’m a Billy Badass service guy and how I’m more awesome than anyone else, but the simple fact is that I’m not. I do things a little differently and think a little differently than many others  and that sets me apart.

What did the first Tech do wrong? While I’m not in his head, I think that he focused on why the heat didn’t work instead of taking the unit AS A WHOLE and diagnose it as a whole. Kind of like the guy who can’t figure out why the fridge is warm and spends an hour working on it only to find the plug pulled.

So, the the mental aspect of troubleshooting cannot be ignored.
Start at the beginning, work the process and troubleshoot the entire system. Being willing to read the manufacturers troubleshooting info isn’t a newbie move, it shows maturity.

Work on the troubleshooting mindset, don’t be a parts changer.

— Jeremy

(Edited by Bryan Orr, any mistakes are my fault)

I have spent the last few days checking run capacitors on various systems with several different meters and this is what I found.

#1 – Comparing Start wire amps against Run + Common under the clamp together is meaningless as a practical test.

I used this test on 3 different systems with 3 different meters and came to the same conclusion, whether the capacitor is way too large, way too small or the right size, made no repeatable difference in the reading no matter how we read it.
Even if this is a valid test (which I cannot confirm at this time) the difference is within the uncertainty tolerance of the meter so it’s not useful for field testing.

#2 – The under load test does work (If your meter works)

reading the amps at the herm (compressor start wire) terminal multiplying by 2652 and dividing by the start voltage (herm to c) on the capacitor does work consistently on the compressor and the fan motor however some meters are less accurate at lower amperage readings so that may make a slight difference.
#3 – Power Factor works as a test but it’s a small change
I tested several systems with the Testo 770-3 in power factor mode by installing too large and too small capacitors. The power factor did decrease in all cases when the incorrect size was installed but in some cases the difference was very slight (from 1 to .99 with a 15 mfd too small run capacitor in one case). This means that while it is a valid and useful test it may not be sensitive enough to act as verfication that a capacitor is slightly outside of allowable specs.
— Bryan

This is a quick article from the archives that got a big response 4 months ago. I also just did a Facebook Live video this morning baring my soul on the topic of flowing nitrogen in response to an Email.


Why is it called single phase 240 when there are two opposing phases?

I wondered why two 120v opposing phases was called “Single phase 240” for years.

Then someone pointed out to me that a typical “single phase” pole transformer only has one power leg entering and two coming out.

This freaked me out. How can a transformer primary be one phase, a SINGLE sine wave and output two perfectly opposing sine phases?

It’s just two separate winding wraps in OPPOSITE directions on the secondary. Stupid simple, but I just never knew it.

So unlike a three phases services that uses all three power phases from the power supply, the single phase service only uses one. The second phase is “created” in the secondary of the distribution transformer itself and is the same “phase” but opposite.

Pretty cool.

— Bryan

This quiz was written by Benoît Mongeau


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