The Untypical Refrigeration System

by Dave Demma

While it might be fair to say that there is no such thing as a typical supermarket refrigeration system, there are commonalities between all systems that employ multiplex compressor racks. It is typical for the evaporator circuits in each supermarket to be combined into common saturated suction temperature (SST) groups, and connected to a multiplex compressor rack designed to operate within that specific temperature range.

It is also typical that there would be several SST groups in a supermarket. For example: medium-temperature (MT) fixtures/boxes at 15˚F and 25˚, and low-temperature (LT) fixtures/boxes at -13˚ and -23˚. It is also typical that there would be a variation of temperatures between the evaporator circuits within each suction group. The circuits connected to the 15˚ MT rack might vary in design from 15˚ for the service deli cases to 25˚ for the bakery walk-in cooler. These variations in design SST require some form of temperature control for each individual evaporator circuit.

But for the last five years, the supermarket industry has undergone a gradual shift in thinking regarding the preferred method for controlling evaporator discharge air temperature. You might call it an untypical … and more modern approach.

Mechanical evaporator pressure regulator (EPR) valves continue to have a strong following, and are still used in the majority of applications. However, the margin over the up-and-coming alternate choice — electric suction line regulators — is shrinking. As the name implies, this is a regulator that is installed in the suction line, and utilizes an electric step motor to drive the piston open or closed. Hence the name electric suction line regulator (Fig. 1).

In this story — the first of a multipart series regarding the changes taking place in supermarket refrigeration — we will look at some of those typical ways of currently doing business and what might be driving the changes that we will look at in future parts of this series.

EVAPORATOR SST

Evaporator SST is the temperature design criteria specified on the supermarket equipment legend. Maintaining a constant evaporator SST can be achieved with a mechanical EPR. It is designed to maintain a constant refrigerant pressure in the evaporator, which then maintains the constant SST. This will provide a fairly constant discharge air temperature, and has been the standard method of circuit temperature control dating back to the 1970s.

There are a few drawbacks to this method of circuit temperature control. There is no perfect correlation between SST and discharge air temperature. As the system conditions and/or the refrigeration load changes, maintaining a constant SST will result in some variation in discharge air temperature (Fig. 2).

This will not be problematic in all applications. Canned beverages and bottled water can certainly tolerate wider temperature swings without the risk of spoilage. In other applications, such as a fresh meat display, precise temperature control is essential for product integrity.

Additionally, more consistent discharge air temperatures may be required to satisfy the requirements of regulations such as HACCP (Hazard Analysis of Critical Control Points) begins with the evaluation of a situation, to assess the possibility of consumer health hazard.

Such an evaluation depends on three factors:

1. Does the product contain contaminant-sensitive ingredients?

2. Does its manufacturing involve a controlled process step such as sufficiently high temperature, pH change, or other process that can eliminate the hazard?

3. Does its distribution chain pose any potential hazard?

In the next step, critical control points (CCPs) are identified with maximum assurance. These are the locations in the processing plant where failure to prevent contamination can be detected through instruments such as recording thermometers.

Multiplex compressor racks are typically controlled by a central processor, commonly referred to as an energy management system (EMS). Amongst its many functions is the ability to control pressure and temperature parameters in the supermarket. It will monitor the evaporator discharge air temperature of each system, and might even have a provision to cycle off a liquid solenoid valve to provide a safety against a low-fixture temperature.

The EMS is capable of providing a control signal in response to a fixture discharge air temperature that has strayed outside of its set-point parameter. While this can be used to generate an alarm for monitoring purposes, the EPR set point cannot be changed with a simple control signal. A setting change of that nature would require an on site technician to make the adjustment.

Herein is the limitation of the mechanical EPR. While it does provide a fairly consistent discharge air temperature by maintaining a constant SST, it cannot be modulated by the EMS when the discharge air temperature strays outside of the design set-point parameter. The inability of the EMS to control the EPR can certainly cause the discharge air temperature to rise above or fall below the design set point.

While the main focus of temperature control is to ensure that the refrigerated product does not suffer a loss of integrity, or prematurely spoil, there is another aspect of display case and/or walk-in box temperature control that should not be overlooked: It is never necessary for the discharge air temperature to fall below the design set point. More importantly, when the discharge air temperature does fall below its set point, it is accomplished by an unnecessary expenditure of energy. 

PULLDOWN AFTER DEFROST

Figure 2. As the system conditions and/or the refrigeration load changes, maintaining a constant SST will result in some variation in discharge air temperature.

Every refrigeration circuit in the supermarket will undergo one or more defrost cycles per day. Regardless of the defrosting method employed (off cycle, electric, gas), the product temperature will be well above its design temperature set point upon termination of the defrost cycle. The evaporator will be under its highest load condition at the very moment the defrost cycle terminates.

EPR will immediately open to 100 percent of its stroke, quickly reducing the evaporator pressure. Once the circuit pressure has been reduced to the EPR set point, the valve will start to throttle in an effort to maintain constant pressure — its design function.

This will happen well before the discharge air temperature has reduced to the design set point. The reason is because the EPR maintains a constant pressure in the evaporator, and only indirectly maintains a relatively constant discharge air temperature. The EPR does not sense discharge air temperature and therefore can do nothing to respond and provide a quicker pull-down after defrost. It can prematurely throttle after the defrost termination in an effort to maintain its control parameter evaporator pressure.

SETTING THE STAGE

All this is setting the stage for increasing use of electric suction line regulators — and that will be the focus of the next installment in this series.

The Basic Refrigeration Cycle

Mechanical refrigeration is accomplished by continuously circulating, evaporating, and condensing a fixed supply of refrigerant in a closed system. Evaporation occurs at a low temperature and low pressure while condensation occurs at a high temperature and high pressure. Thus, it is possible to transfer heat from an area of low temperature (i.e., refrigerator cabinet) to an area of high temperature (i.e., kitchen).

Referring to the illustration below, beginning the cycle at the evaporator inlet (1), the low-pressure liquid expands, absorbs heat, and evaporates, changing to a low-pressure gas at the evaporator outlet (2).

The compressor (4) pumps this gas from the evaporator through the accumulator (3), increases its pressure, and discharges the high-pressure gas to the condenser (5). The accumulator is designed to protect the compressor by preventing slugs of liquid refrigerant from passing directly into the compressor. An accumulator should be included on all systems subjected to varying load conditions or frequent compressor cycling. In the condenser, heat is removed from the gas, which then condenses and becomes a high-pressure liquid. In some systems, this high-pressure liquid drains from the condenser into a liquid storage or receiver tank (6). On other systems, both the receiver and the liquid line valve (7) are omitted.

A heat exchanger (8) between the liquid line and the suction line is also an optional item, which may or may not be included in a given system design.

Illustration of the basic refrigeration cycle.

Between the condenser and the evaporator an expansion device (10) is located. Immediately preceding this device is a liquid line strainer/drier (9), which prevents plugging of the valve or tube by retaining scale, dirt, and moisture. The flow of refrigerant into the evaporator is controlled by the pressure differential across the expansion device or, in the case of a thermal expansion valve, by the degree of superheat of the suction gas. Thus, the thermal expansion valve shown requires a sensor bulb located at the evaporator outlet. In any case, the flow of refrigerant into the evaporator normally increases as the evaporator load increases.

As the high-pressure liquid refrigerant enters the evaporator, it is subjected to a much lower pressure due to the suction of the compressor and the pressure drop across the expansion device. Thus, the refrigerant tends to expand and evaporate. In order to evaporate, the liquid must absorb heat from the air passing over the evaporator.

Eventually, the desired air temperature is reached and the thermostat or cold control (11) will break the electrical circuit to the compressor motor and stop the compressor.

As the temperature of the air through the evaporator rises, the thermostat or cold control remakes the electrical circuit. The compressor starts, and the cycle continues.

In addition to the accumulator, a compressor crankcase heater (12) is included on many systems. This heater prevents accumulation of refrigerant in the compressor crankcase during the non-operating periods and prevents liquid slugging or oil pumpout on startup.

Additional protection to the compressor and system is afforded by a high- and low-pressure cutout (13). This control is set to stop the compressor in the event that the system pressures rise above or fall below the design operating range.

Other controls not indicated on the basic cycle which may be part of a system include: evaporator pressure regulators, hot gas bypass regulators, electric solenoid valves, suction pressure regulators, condenser pressure regulators, low-side or high-side float refrigerant controllers, oil separators, etc.

It is extremely important to analyze completely every system and understand the intended function of each component before attempting to determine the cause of a malfunction or failure.

Air Conditioning and Refrigeration History

But the engineering principle on which it is based, mechanical refrigeration, has had even more far-reaching effects, through both refrigeration itself and its close cousin, air conditioning. Taken together, these cooling technologies have altered some of our most fundamental patterns of living. Our daily chores are different. What we eat and how we prepare food have both changed. The kinds of buildings we live and work in and even where we choose to live across the whole length and breadth of the United States all changed as a result of 20th-century expertise at keeping things cool.

Look back for a moment to the world before the widespread use of refrigeration and air conditioning—a world that was still very much present well into the first decades of the 20th century. Only fresh foods that could be grown locally were available, and they had to be purchased and used on a daily basis. Meat was bought during the daily trip to the butcher's; the milkman made his rounds every morning. If you could afford weekly deliveries of ice blocks—harvested in the winter from frozen northern lakes—you could keep some perishable foods around for 2 or 3 days in an icebox. As for the nonexistence of air conditioning, it made summers in southern cities—and many northern ones—insufferable. The nation's capital was a virtual ghost town in the summer months. As late as the 1940s, the 60-story Woolworth Building and other skyscrapers in New York City were equipped with window awnings on every floor to keep direct sunlight from raising temperatures even higher than they already were. Inside the skyscrapers, ceiling and table fans kept the humid air from open windows at least moving around. Throughout the country, homes were built with natural cooling in mind. Ceilings were high, porches were deep and shaded, and windows were placed to take every possible advantage of cross-ventilation.

By the end of the century all that had changed. Fresh foods of all kinds were available just about anywhere in the country all year round—and what wasn't available fresh could be had in convenient frozen form, ready to pop into the microwave. The milkman was all but gone and forgotten, and the butcher now did his work behind a counter at the supermarket. Indeed, many families concentrated the entire week's food shopping into one trip to the market, stocking the refrigerator with perishables that would last a week or more. And on the air-conditioning side of the equation, just about every form of indoor space—office buildings, factories, hospitals, and homes—was climate-controlled and comfortable throughout the year, come heat wave or humidity. New homes looked quite different, with lower rooflines and ceilings, porches that were more for ornament than practicality, and architectural features such as large plate glass picture windows and sliding glass doors. Office buildings got a new look as well, with literally acres of glass stretching from street level to the skyscraping upper floors. Perhaps most significant of all, as a result of air conditioning, people started moving south, reversing a northward demographic trend that had continued through the first half of the century. Since 1940 the nation's fastest-growing states have been in the Southeast and the Southwest, regions that could not have supported large metropolitan communities before air conditioning made the summers tolerable

Mechanical refrigeration, whether for refrigeration itself or for air conditioning, relies on a closed system in which a refrigerant—basically a compound of elements with a low boiling point—circulates through sets of coils that absorb and dissipate heat as the refrigerant is alternately compressed and allowed to expand. In a refrigerator the circulating refrigerant draws heat from the interior of the refrigerator, leaving it cool; in an air conditioner, coils containing refrigerant perform a similar function by drawing heat and moisture from room air.

This may sound simple, but it took the pioneering genius of a number of engineers and inventors to work out the basic principles of cooling and humidity control. Their efforts resulted in air conditioning systems that not only were a real benefit to the average person by the middle of the 20th century but also made possible technologies in fields ranging from medical and scientific research to space travel.

Prominent among air-conditioning pioneers was Willis Haviland Carrier. In 1902, Carrier, a recent graduate of Cornell University's School of Engineering, was working for the Buffalo Forge Company on heating and cooling systems. According to Carrier, one foggy night while waiting on a train platform in Pittsburgh he had a sudden insight into a problem he had been puzzling over for a while—the complex relationship between air temperature, humidity, and dew point. He realized that air could be dried by saturating it with chilled water to induce condensation. After a number of experimental air conditioning installations, he patented Dew Point Control in 1907, a device that, for the first time, allowed for the precise control of temperature and humidity necessary for sophisticated industrial processes. Carrier's early air conditioner was put to use right away by a Brooklyn printer who could not produce a good color image because fluctuations of heat and humidity in his plant kept altering the paper's dimensions and misaligning the colored inks. Carrier's system, which had the cooling power of 108,000 pounds of ice a day, solved the problem. That same principle today makes possible the billion-dollar facilities required to produce the microcircuits that are the backbone of the computer industry. Air conditioners were soon being used in a variety of industrial venues. The term itself was coined in 1906 by a man named Stuart Cramer, who had applied for a patent for a device that would add humidity to the air in his textile mill, reducing static electricity and making the textile fibers easier to work with. Air-conditioning systems also benefited a host of other businesses, enumerated by Carrier himself: "lithography, the manufacture of candy, bread, high explosives and photographic films, and the drying and preparing of delicate hygroscopic materials such as macaroni and tobacco." At the same time, it did not go unnoticed that workers in these air-conditioned environments were more productive, with significantly lower absentee rates. Comfort cooling, as it became known, might just be a profitable commodity in itself.

Carrier and others set out to explore the potential. In 1915 he and several partners formed the Carrier Engineering Corporation, which they dedicated to improving the technology of air conditioning. Among the key innovations was a more efficient centrifugal (as opposed to piston-driven) compressor, which Carrier used in the air conditioners he installed in Detroit's J. L. Hudson Department Store in 1924, the first department store so equipped. Office buildings soon followed.  


Even as Willis Carrier was pioneering innovations in industrial air conditioners, a number of others were doing the same for comfort cooling. Beginning in 1899, consulting engineer Alfred Wolff designed a number of cooling systems, including prominent installations at the New York Stock Exchange, the Hanover National Bank, and the New York Metropolitan Museum of Art. The public was exposed to air conditioning en masse at the St. Louis World's Fair in 1904, where they enjoyed the air-conditioned Missouri State Building. Dozens of movie theaters were comfort cooled after 1917, the result of innovations in theater air conditioning by Fred Wittenmeier and L. Logan Lewis, with marquees proclaiming "It's 20 degrees cooler inside." Frigidaire engineers introduced a room cooler in 1929, and they, along with other companies such as Kelvinator, General Electric, and York, pioneered fully air-conditioned homes soon after.

Refrigerators did not represent quite as much of a revolution. Many people at the turn of the century were at least familiar with the concept of a cool space for storing food—the icebox. But true mechanical refrigeration—involving that closed system of circulating refrigerant driven by a compressor—didn't come along in any kind of practical form until 1913. In that year a man named Fred Wolf invented a household refrigerator that ran on electricity (some earlier mechanical refrigerators had run on steam-driven compressors that were so bulky they had to be housed in a separate room). He called it the Domelre, for Domestic Electric Refrigerator, and sold it for $900. It was a quick hit but was still basically an adaptation of the existing icebox, designed to be mounted on top of it. Two years later Alfred Mellowes introduced the first self-contained mechanical refrigerator, which was marketed by the Guardian Refrigerator Company. Mellowes had the right idea, but Guardian didn't make what it could of it. In 2 years the company produced a mere 40 machines.

Into the breach stepped one of the giants of the automotive industry, William Durant, president of General Motors. Realizing the potential of Guardian's product, he bought the company in 1918, renamed it Frigidaire, and put some of GM's best engineering and manufacturing minds to work on mass production. A few years later Frigidaire also bought the Domelre patent and began churning out units, introducing improvements with virtually each new production run.

Other companies, chief among them Kelvinator and General Electric, added their own improvements in a quest for a share of this obviously lucrative new market. By 1923 Kelvinator, which had introduced the first refrigerator with automatic temperature control, held 80 percent of market share, but Frigidaire regained the top in part by cutting the price of its units in half—from $1,000 in 1920 to $500 in 1925. General Electric ended up as industry leader for many years with its Monitor Top model—named because its top—mounted compressor resembled the turret of the Civil War ship-and with innovations such as dual temperature control, which enabled the combining of separate refrigerator and freezer compartments into one unit. 


Market forces and other concerns continued to drive innovations. Led by Thomas Midgley, chemical engineers at Frigidaire solved the dangerous problem of toxic, flammable refrigerants—which had been known to leak, with fatal consequences—by synthesizing the world's first chlorofluorocarbon, to which they gave the trademarked name Freon. It was the perfect refrigerant, so safe that at a demonstration before the American Chemical Society in 1930 Midgley inhaled a lungful of the stuff and then used it to blow out a candle. In the late 1980s, however, chlorofluorocarbons were found to be contributing to the destruction of Earth's protective ozone layer. Production of these chemicals was phased out and the search for a replacement began.

At about the same time Frigidaire was introducing Freon it also turned its attention to the other side of the mechanical refrigeration business: air conditioning. Comfort cooling for the home had been hampered by the fact that air conditioners tended to be bulky affairs that had been designed specifically for large-scale applications such as factories, theaters, and the like. In 1928 Carrier introduced the "Weathermaker," the first practical home air conditioner, but because the company's main business was still commercial, it was slow to turn to the smaller-scale designs that residential applications required. Frigidaire, on the other hand, was ready to apply the same expertise in engineering and manufacturing that had allowed it to mass produce—literally by the millions—the low-cost, small-sized refrigerators that were already a fixture in most American homes. In 1929 the company introduced the first commercially successful "room cooler," and a familiar list of challengers—Kelvinator, GE, and this time Carrier—quickly took up the gauntlet. Window units came first, then central whole-house systems. Without leaving home, Americans could now escape everything from the worst humid summers of the Northeast and Midwest to the year-round thermometer-busting highs of the South and desert Southwest.

At about the same time that both refrigeration and air conditioning were becoming significantly more commonplace, both also went mobile. In 1939 Packard introduced the first automobile air conditioner, a rather awkward affair with no independent shut-off mechanism. To turn it off, the driver had to stop the car and the engine and then open the hood and disconnect a belt connected to the air conditioning compressor. Mechanical engineers weren't long in introducing needed improvements, ultimately making air conditioning on wheels so de rigueur that even convertibles had it.

But as wonderful as cool air for summer drives was, it didn't have anywhere near the impact of the contribution of Frederick McKinley Jones, an inventor who was eventually granted more than 40 patents in the field of refrigeration and more than 60 overall. On July 12, 1940, Jones—a mechanic by training but largely self-taught—was issued a patent for a roof-mounted cooling device that would refrigerate the inside of a truck. Jones's device was soon adapted for use on trains and ships. Hand in hand with Clarence Birdseye's invention of flash freezing, Jones's refrigeration system made readily available—no matter what the season—all manner of fresh and frozen foods from every corner of the nation and, indeed, the world.

Small but incrementally significant improvements continued as the century unfolded, making refrigeration and air conditioning systems steadily more efficient and more affordable—and increasingly widespread. The range of applications has grown as well, with mechanical refrigeration playing a role in everything from medical research and computer manufacturing to space travel. Without, for example, the controlled, air-conditioned environment in spacecraft and spacesuits, humans would never have made it into space—or walked on the Moon—-even with all the other engineering hurdles overcome. But most of us don't have to go quite so far to appreciate the benefits of keeping cool. They're right there for us, each time we open the refrigerator door and reach for something cold to drink.

Air Conditioning and Refrigeration

Which of the appliances in your home would be the hardest to live without? The most frequent answer to that question in a recent survey was the refrigerator. Over the course of the 20th century, this onetime luxury became an indispensable feature of the American home, a mainstay in more than 99.5 percent of the nation's family kitchens by century's end. 

  
Air Conditioning and Refrigeration Timeline
  
Keeping cool has been a human preoccupation for millennia, but until the 20th century most efforts were ineffective. People tried everything from draping saturated mats in doorways to the installation of water-powered fans. Even Leonardo da Vinci designed and built a mechanical ventilating fan, the first of its kind. The modern system—involving the exchange of hot, moist air for cool, dry air by way of a circulating refrigerant—was first used in industrial settings. Indeed, a North Carolina textile engineer named Stuart Cramer, impressed with how the latest system of controlling the heat and humidity in his plant improved the cloth fibers, coined the term "air conditioning" in 1906. Since then comfort of cool is no longer considered a luxury but a fact of modern existence.

      1902~Comfort cooling system installed at the New York Stock Exchange

A 300-ton comfort cooling system designed by Alfred Wolff is installed at the New York Stock Exchange. Using free cooling provided by waste-steam-operated refrigeration systems, Wolff’s system functions successfully for 20 years.

      1902~First office building with an air-conditioning system installed

The Armour Building in Kansas City, Missouri, becomes the first office building to install an air-conditioning system. Each room is individually controlled with a thermostat that operates dampers in the ductwork, making it also the first office building to incorporate individual "zone" control of separate rooms.

      1904~A self-contained mechanical refrigerator is displayed at the St. Louis World's Fair

A self-contained mechanical refrigerator is displayed at the St. Louis World's Fair by Brunswick Refrigerating Co., which specializes in designing small refrigerators for residences and butcher shops. The ammonia refrigerating system is mounted on the side of a wooden icebox-type refrigerator.

Thousands of attendees at the World's Fair also experience the public debut of air conditioning in the Missouri State Building. The system uses 35,000 cubic feet of air per minute to cool a 1,000- seat auditorium, the rotunda, and various other rooms.

      1906~First office building specifically designed for air conditioning.

In Buffalo, Frank Lloyd Wright’s Larkin Administration Building is the first office building specifically designed for air conditioning. The system uses safe, nonflammable carbon dioxide as a refrigerant.

      1906~Patent filed for "dew point control" system

Willis Carrier files for a patent on his "dew point control" system. Carrier has studied the science of humidity control after designing a rudimentary air-conditioning system for a Brooklyn printing plant in 1902. This and subsequent designs allow him to devise a precise method of controlling humidity using refrigerated water sprays, thereby allowing the manufacture of air-conditioning systems to be standardized.

      1906~First air-conditioned hospital

Boston Floating Hospital becomes the first air-conditioned hospital, using a system designed by Edward Williams to maintain the hospital wards at about 70°F with a relative humidity of 50 percent. The hospital’s five wards are individually controlled by thermostats. Williams’s system features "reheat" in which cooled air is heated slightly to lower its humidity.

      1907~Air-conditioning equipment installed in dining and meeting rooms at Congress Hotel in Chicago

Air-conditioning equipment designed by Frederick Wittenmeier is installed in dining and meeting rooms at Congress Hotel in Chicago. This is one of the first systems designed by Wittenmeier for hotels and movie theaters. His firm, Kroeschell Brothers Ice Machine Company, installs hundreds of cooling plants into the 1930s.

      1914~Aircooled, electric, self-contained household refrigerating unit is marketed

Fred Wolf, Jr., markets an aircooled, electric, self-contained household refrigerating unit, the Domelre (Domestic Electric Refrigerator), in Chicago. The system is designed to be placed on top of any icebox, operating automatically using a thermostat. The first household refrigerating system to feature ice cubes, the Domelre uses air to cool the condenser, unlike other household refrigerators that need to be hooked up to water.

      1916~Flash-freezing system for preserving food products developed

Clarence Birdseye begins experiments in quick-freezing. Birdseye develops a flash-freezing system that moves food products through a refrigerating system on conveyor belts. This causes the food to be frozen very fast, minimizing ice crystals.

      1923~Electrically refrigerated ice cream dipping cabinet is marketed

An electrically refrigerated ice cream dipping cabinet is marketed by Nizer and shortly after by Frigidaire. These cabinets use a refrigeration system to chill alcohol-based antifreeze, which surrounds ice cream cans placed in wells in the cabinet. The alcohol is later replaced by salt brine.

      1927~Gas-fired household absorption refrigerators become popular

Gas-fired household absorption refrigerators that do not require electricity are marketed to rural areas in the United States. One, the Electrolux, marketed in Sweden since 1925, becomes very popular.

      1927~First refrigerator to be mass produced with a completely sealed refrigerating system

General Electric introduces the first refrigerator to be mass produced with a completely sealed refrigerating system. Nicknamed "The Monitor Top" for its distinctive round refrigerating unit, resembling the gun turret of the Civil War ironclad ship Monitor, the refrigerator is produced over the next 10 years and is so reliable that thousands are still in use today.

      1928~Chlorofluorocarbon (CFC) refrigerants are synthesized

Chlorofluorocarbon (CFC) refrigerants are synthesized for Frigidaire by the General Motors Research Lab team of Thomas Midgley, Albert Henne, and Robert McNary. Announced publicly in 1930 and trademarked as Freon, CFCs are the first nontoxic and nonflammable refrigerating fluids, making it possible for refrigerators and air conditioners to be used with complete safety.

      1929~First room cooler goes on the market

Frigidaire markets the first room cooler. The refrigeration unit, which uses sulfur dioxide refrigerant and has a capacity of one ton (12,000 BTUH), is designed to be located outside the house or in the basement.

      1930~Smaller air-conditioning units appear on trains

With the advent of the centrifugal chiller, smaller air-conditioning units become feasible for trains. In 1930 the Baltimore & Ohio Railroad tests a unit designed by Willis Carrier on the "Martha Washington" the dining car on the Columbian, running between Washington, D.C. and New York. To test the system, the car is heated to 93°F. The heat is then turned off and the air conditioner turned on. Within 20 minutes, the temperature in the dining car is a comfortable 73°F.

      1931~"Hot- Kold" year-round central air-conditioning system for homes on the market

Frigidaire markets the "Hot- Kold" year-round central air-conditioning system for homes. During the early 1930s, a number of manufacturers design central air conditioners for homes, a market that grows slowly until the 1960s, when lower costs make it affordable for many new homes.

      1931~ A heat pump air-conditioning system in Los Angeles office building

Southern California Edison Company installs a heat pump air-conditioning system in its Los Angeles office building. Since a refrigeration system moves heat from one place to another, the same principle can be used to remove heat in summer or add heat in winter by engineering the system to be reversible.

      1932~First overnight train with air conditioning

Chesapeake & Ohio Railroad begins running the first overnight train with air conditioning, the George Washington, between New York and Washington. Four years later United Air Lines uses air conditioning in its "three miles a minute" passenger planes.

      1936~Albert Henne synthesizes refrigerant R-134a

Albert Henne, coinventor of the CFC refrigerants, synthesizes refrigerant R-134a. In the 1980s this refrigerant is hailed as the best nonozone-depleting replacement for CFCs.

      1938~A window air conditioner using Freon is marketed

A window air conditioner using Freon is marketed by Philco-York. Featuring a beautiful wood front, the Philco air conditioner can simply be plugged into an electrical outlet.

      1939~Air conditioning offered as an option in a Packard automobile

Packard Motor Car Company markets an automobile with air conditioning offered as an option for $274. The refrigeration compressor runs off the engine, and the system has no thermostat. It discharges the cooled air from the back of the car.

      1947~Mass-produced, low-cost window air conditioners become possible

Mass-produced, low-cost window air conditioners become possible as a result of innovations by engineer Henry Galson, who sets up production lines for a number of manufacturers. In 1947, 43,000 window air conditioners are sold in the United States. For the first time, many homeowners can enjoy air conditioning without having to buy a new home or renovate their heating system.

      1969~More than half of new automobiles are equipped with air conditioning

More than half of new automobiles (54 percent) are equipped with air conditioning, which is soon a necessity, not only for comfort but also for resale value.

By now, most new homes are built with central air conditioning, and window air conditioners are increasingly affordable.

      1987~Minimum energy efficiency requirements set

The National Appliance Energy Conservation Act mandates minimum energy efficiency requirements for refrigerators and freezers as well as room and central air conditioners.

      1987~The Montreal Protocol

The Montreal Protocol serves as an international agreement to begin phasing out CFC refrigerants, which are suspected of contributing to the thinning of the earth’s protective, high-altitude ozone shield.

      1992~Minimum energy efficiency standards set for commercial buildings

The U.S. Energy Policy Act mandates minimum energy efficiency standards for commercial buildings, using research and standards developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers.

Chillers

Introduction

Chillers are a key component of air conditioning systems for large buildings. They produce cold water to remove heat from the air in the building. They also provide cooling for process loads such as file-server rooms and large medical imaging equipment. As with other types of air conditioning systems, most chillers extract heat from water by mechanically compressing a refrigerant.

Chillers are complex machines that are expensive to purchase and operate. A preventive and predictive maintenance program is the best protection for this valuable asset.

Learn more about establishing a Best Practice O&M Program.

Chillers commonly use more energy than any other piece of equipment in large buildings. Maintaining them well and operating them smartly can yield significant energy savings.

 Chiller and associated HVAC systems

Types of Chillers

Mechanical Compression
During the compression cycle, the refrigerant passes through four major components within the chiller: the evaporator, the compressor, the condenser, and a flow-metering device such as an expansion valve. The evaporator is the low-temperature (cooling) side of the system and the condenser is the high-temperature (heat-rejection) side of the system.

 The refrigeration cycle

Mechanical Compressor Chillers

Mechanical compression chillers are classified by compressor type: reciprocating, rotary screw, centrifugal and frictionless centrifugal.

Reciprocating: Similar to a car engine with multiple pistons, a crankshaft is turned by an electric motor, the pistons compress the gas, heating it in the process. The hot gas is discharged to the condenser instead of being exhausted out a tailpipe. The pistons have intake and exhaust valves that can be opened on demand to allow the piston to idle, which reduces the chiller capacity as the demand for chilled water is reduced. This unloading allows a single compressor to provide a range of capacities to better match the system load. This is more efficient than using a hot-gas bypass to provide the same capacity variation with all pistons working. Some units use both methods, unloading pistons to a minimum number, then using hot-gas bypass to further reduce capacity stably. Capacities range from 20 to 125 tons.

 Reciprocating compressor

Rotary Screw: The screw or helical compressor has two mating helically grooved rotors in a stationary housing. As the helical rotors rotate, the gas is compressed by direct volume reduction between the two rotors. Capacity is controlled by a sliding inlet valve or variable-speed drive (VSD) on the motor. Capacities range from 20 to 450 tons.

Screw compressor

Centrifugal: The centrifugal compressor operates much like a centrifugal water pump, with an impeller  compressing the refrigerant. Centrifugal chillers provide high cooling capacity with a compact design. They can be equipped with both inlet vanes and variable-speed drives to regulate control chilled water capacity control. Capacities are 150 tons and up.

Centrifugal compressor

Frictionless Centrifugal: This highly energy-efficient design employs magnetic bearing technology. The compressor requires no lubricant and has a variable-speed DC motor with direct-drive for the centrifugal compressor. Capacities range from 60 to 300 tons.

Turbocor© frictionless centrifugal compressor

Absorption Chillers

Absorption chillers use a heat source such as natural gas or district steam to create a refrigeration cycle that does not use mechanical compression. Because there are few absorption machines in the Northwest U.S., this document covers only mechanical-compression chillers. You can learn more about absorption chillers at the Energy Solutions Center.
Key Components of Mechanical Compression Chillers
Evaporator

Chillers produce chilled water in the evaporator where cold refrigerant flows over the evaporator tube bundle. The refrigerant evaporates (changes into vapor) as the heat is transferred from the water to the refrigerant. The chilled water is then pumped, via the chilled-water distribution system to the building’s air-handling units.

The chilled water passes through coils in the air-handler to remove heat from the air used to condition spaces throughout the building. The warm water (warmed by the heat transferred from the building ventilation air) returns to the evaporator and the cycle starts over.
 
Compressor
Vaporized refrigerant leaves the evaporator and travels to the compressor where it is mechanically compressed, and changed into a high-pressure, high-temperature vapor. Upon leaving the compressor, the refrigerant enters the condenser side of the chiller.
Condenser

Inside the water-cooled condenser, hot refrigerant flows around the tubes containing the condenser-loop water. The heat transfers to the water, causing the refrigerant to condense into liquid form. The condenser water is pumped from the condenser bundle to the cooling tower where heat is transferred from the water to the atmosphere. The liquid refrigerant then travels to the expansion valve.

The refrigerant flows into the evaporator through the expansion valve or metering device. This valve controls the rate of cooling. Once through the valve, the refrigerant expands to a lower pressure and a much lower temperature. It flows around the evaporator tubes, absorbing the heat of the chilled water that’s been returned from the air handlers, completing the refrigeration cycle.

Controls
Newer chillers are controlled by sophisticated, on-board microprocessors. Chiller control systems include safety and operating controls. If the equipment malfunctions, the safety control shuts the chiller down to prevent serious damage to the machine. Operating controls allow adjustments to some chiller operating parameters. To better monitor chiller performance, the chiller control system should communicate with the facility’s direct digital control (DDC).
Safety Issues

Chillers are typically located in a mechanical equipment rooms. Each type of refrigerant used in a chiller compressor has specific safety requirements for leak detection and emergency ventilation. Consult your local mechanical code or the International Mechanical Code for details.

The EPA has enacted regulations regarding the use and handling of refrigerants to comply with the Clean Air Act of 1990. All personnel working with refrigerants covered by this act must be appropriately licensed.
Best Practices for Efficient Operation

The following best practices can improve chiller performance and reduce operating costs:

Operate multiple chillers for peak efficiency: Plants with two or more chillers can save energy by matching the building loads to the most efficient combination of one or more chillers. In general, the most efficient chiller should be first one used.

Raise chilled-water temperature: An increase in the temperature of the chilled water supplied to the building’s air handlers will improve its efficiency. Establish a chilled-water reset schedule. A reset schedule can typically adjust the chilled-water temperature as the outside-air temperature changes. On a centrifugal chiller, increasing the temperature of chilled water supply by 2–3°F will reduce chiller energy use 3–5%.

Reduce condenser water temperature: Reducing the temperature of the water returning from the cooling tower to the chiller condenser by 2–3°F will reduce chiller energy use 2–3%. The temperature setpoint for the water leaving the cooling tower should be as low as the chiller manufacturer will allow for water entering the condenser. The actual leaving tower water temperature may be limited by the ambient wet bulb temperature.

Purge air from refrigerant: Air trapped in the refrigerant loop increases pressure at the compressor discharge. This increases the work required from the compressor. Newer chillers have automatic air purgers that have run-time meters. Daily or weekly tracking of run time will show if a leak has developed that permits air to enter the system.

Optimize free cooling: If your system has a chiller bypass and heat exchanger, known as a water-side economizer, it should be used to serve process loads during the winter season. The water-side economizer produces chilled water without running the chiller. Condenser water circulates through the cooling tower to reject heat, and then goes to a heat exchanger (bypassing the chiller) where the water is cooled sufficiently to meet the cooling loads.

Verify Performance of hot-gas bypass and unloader: These are most commonly found on reciprocating compressors to control capacity. Make sure they operate properly.

Maintain refrigerant level: To maintain a chiller's efficiency, check the refrigerant sight-glass and the superheat and subcooling temperature readings, and compare them to the manufacturer’s requirements. Both low-level and high-level refrigerant conditions can be detected this way. Either condition reduces a chiller’s capacity and efficiency.

Maintain a daily log: Chiller O&M best practices begin with maintaining a daily log of temperatures, fluid levels, pressures, flow rates, and motor amperage. Taken together, these readings serve as a valuable baseline reference for operating the system and troubleshooting problems. Many newer chillers automatically save logs of these measurements in their on-board control system, which may be able to communicate directly with the DDC system. Below is an example of a daily log that can be adapted for use with your chiller.

Best Practices for Maintenance

Compared to a major chiller failure, a sound preventive and predictive maintenance program is a minor cost. Implementing a best-practice maintenance plan will save money over the life of the chiller and ensure longer chiller life. For more information on this topic go to Best Practice O&M Program.

Substandard operating practices frequently go unnoticed and become the accepted norm. Training personnel in both maintenance and operating practices is the best prevention. Many chiller manufacturers offer training for building operating engineers in operating and maintaining their chillers.

To effectively maintain chillers, you must 1) bring the chiller to peak efficiency, and 2) maintain that peak efficiency. There are some basic steps that facilities professionals can take to make sure their chillers are being maintained properly. Below are some of the key practices.
Reduce Scale or Fouling

Failure of the heat exchanger tubes is costly and disruptive. The evaporator and condenser tube bundles collect mineral and sludge deposits from the water. Scale buildup promotes corrosion that can lead to the failure of the tube wall. Scale buildup also insulates the tubes in the heat exchanger reducing the efficiency of the chiller. There are two main preventive actions:

Checking water treatment: Checking the water treatment of the condenser-water open loop weekly will reduce the frequency of condenser tube cleaning and the possibility of a tube failure.

Learn more about Operation and Maintenance of Cooling Towers.

Checking the water treatment of the chilled-water closed loop monthly will reduce the frequency of evaporator tube cleaning and the possibility of a tube failure.

Inspecting and cleaning tubes: The tubes in the evaporator and condenser bundles should be inspected once a year, typically when the chiller is taken offline for winterizing. Alternately, for systems that operate all year to meet process loads, tube scaling and fouling can be monitored by logging pressure drop across the condenser and evaporator bundles. An increase in pressure from the inlet to the outlet of 3–4 PSI indicates a probable increase in scale or fouling requiring tube cleaning.
Inspect for Refrigerant Leaks

If possible, monitor the air-purge run timer. Excessive or increased air-purge time may indicate a refrigerant leak. If an air-purge device is not installed, bubbles in the refrigerant sight-glass may also indicate refrigerant leak. Gas analyzers can also be used to identify refrigerant leaks.

The table below provides a checklist for maintenance tasks.

Maintenance Schedule for Chillers
Description	Comments	Maintenance Frequency
Fill out daily log	Check all setpoints for proper setting and function. Make sure there are no unusual sounds and the space temperature is acceptable.	Daily (4x)
Chiller use/sequencing	Turn off or sequence unnecessary chillers	Daily
Check chilled water reset settings and function	Check settings for approved sequence of operation at the beginning of each cooling season	Annually
Check chiller lockout setpoint	Check settings for approved sequence of operation at the beginning of each cooling season	Annually
Clean evaporator and condenser tubes	Indicated when pressure drop across the barrel (tube bundle) exceeds manufacturer's recommendations, but at least annually.	Annually
Verify motor amperage load limit	Motor amperage should not exceed manufacturer's specification	Annually
Compressor motor and assembly	Conduct vibration analysis: Check all alignments to specifications. Check all seals. Lubricate where necessary.	Annually
Compressor oil system	Perform analysis on oil and filter. Change if necessary. Check oil pump and seals Check oil heater and thermostat Check all strainers, valves, etc.	Annually
Electrical connections	Check all electrical connections and terminals for full contact and tightness	Annually
Check refrigerant condition	Add refrigerant if low. Record amounts and address leakage problems.	Annually
Check for condenser and evaporator tube corrosion and clean as needed.	Indications include: poor water quality, excessive fouling, and age of chiller. Eddy current testing may be done to assess tube condition.	As needed

HVAC Acronyms & HVAC Terms

This is a comprehensive list of HVAC Acronyms and HVAC Terms. High Performance HVAC is certain there are more terms and acronyms.

• AC - Air Conditioning or Alternating Current
• ACCA - Air Conditioning Contractors Associations
• AFUE - Annual Fuel Utilization Efficiency
• AHU - Air Handling Unit
• AI - Analog Input
• AMCA - Air Movement and Control Association
• AO - Analog Output
• AQS - Air Quality Systems
• ASHRAE - American Society of Heating, Refrigerating, and Air Conditioning Engineers
• AV - Automatic Air Vent
• AWG - American Wire Gage

1. B - Boiler
2. BACnet - Computer communication protocol for building automation systems and control networks
3. BAS - Building Automation System
4. BI - Binary Input
5. BMS - Building Management System
6. BO - Binary Output
7. BP - Backflow Preventer
8. BTU - British Thermal Unit
9. BTUh - Brtish Thermal Units per Hour

• CAV - Constant Air Volume
• CD - Cold Deck (also Condensation Drain)
• CFC - ChloroFluoroCarbon
• CFM - Cubic Feet per Minute
• CHR - Chilled Water Return (can also have an S in front of the acronym which stands for Secondary when secondary water loops have secondary loops)
• CHS - Chilled Water Supply (can also have an S in front of the acronym which stands for Secondary when secondary water loops have secondary loops)
• CHWP - Chilled Water Pump  (can also have an S in front of the acronym which stands for Secondary when secondary water loops have secondary loops)
• CHWR - Chilled Water Return (can also have an S in front of the acronym which stands for Secondary when secondary water loops have secondary loops)
• CHWS - Chilled Water Supply (can also have an S in front of the acronym which stands for Secondary when secondary water loops have secondary loops)
• CO - Clean Out (also Carbon Monoxide)
• COP - Coefficienct of Performance
• CRAC - Computer Room Air Conditioner
• CRAH - Computer Room Air Handler
• CSR - Capacitor Start Capacitor Run
• CV - Constant Volume
• CWP - Condenser Water Pump
• CWR - Condenser Water Return
• CWS - Condenser Water Supply

1. DA - Discharge Air or Direct Acting
2. DAT - Discharge Air Temperature
3. DB - Dry Bulb or Dead Band
4. DC - Direct Current
5. DCBP - Double Check Backflow Preventer
6. DD - Degree Day
7. DDC - Direct Digital Control
8. DI - Digital Input
9. DO - Digital Output
10. DP - Differential Pressure
11. DPDT - Double Pole Double Throw
12. DPST - Double Pole Single Throw
13. DSI - Direct Spark ignition
14. DX - Direct Expansion

• EDR - Equivalent Direct Radiation
• EER - Energy Efficiency Ratio
• EMF - Electromotive Force
• EF - Exhaust Fan
• EMCS - Energy Management Control System
• EMS - Energy Management System
• EP - Electric to Pnuematic
• ERV - Energy Recovery Ventilator
• EXV - Electronic Expansion Valve

1. FA - Fire Alarm
2. FAI - Fresh Air Intake
3. FCU - Fan Coil Unit
4. FD - Fire Damper
5. FLA - Full Load Amps
6. FPM - Feet Per Minute
7. FPVAV - Fan Powered Variable Air Volume Box
8. FS - Float Switch
9. F & T - Float & Thermostatic

• GPM - Gallons per Minute
• GWP - Global Warming Potential

1. HEPA - High Efficiency Particulate Arresting
2. HCFC - HydroChloroFluoroCarbon
3. HD - Hot Deck
4. HFC - HydroFluoroCarbon
5. HOA - Hand Off Auto
6. HP - High Pressure or Horse Power
7. HPS - High Pressure Steam
8. HRU - Heat Recovery Unit
9. HRV - Heat Recovery Ventilator
10. HSI - Hot Surface Ignition
11. HSPF - Heating Seasonal Performance Factor
12. HSTAT - Humidistat
13. HVAC - Heating, Ventilation, & Air Conditioning
14. HVAC&R - Heating, Ventilation, Air Conditioning, & Refrigeration
15. HWP - Hot Water Pump
16. HWR - Hot Water Return (can also have an S in front of the acronym which stands for Secondary when hot water loops have secondary loops)
17. HWS - Hot Water Supply (can also have an S in front of the acronym which stands for Secondary when hot water loops have secondary loops)
18. HWUH - Hot Water Unit Heater
19. HX - Heat Exchanger
20. HZ - Hertz

• I/O - Input/Output
• IAQ - Indoor Air Quality
• IMC - International Mechanical Code
• in. Hg - inches of mercury vacuum
• in. WC - inches of Water Column
• IRH - InfraRed Heater

          JB - Junction Box

1. KO - Knock Out
2. KW - Kilowatts

• LL - Low Limit
• LP - Low Pressure or Liquified Petroleum
• LPS - Low Pressure Steam
• LRA - Locked Rotor Amps
• LWCO - Low Water Cut Off

1. MA - Mixed Air
2. MAT - Mixed Air Temperature
3. MAU - Make-up Air Unit
4. MCC - Motor Control Center
5. MFD - Micro-Farad
6. MP - Motor Protector
7. MPT - Male Pipe Thread
8. MUW - Make-up Water
9. MV - Manual Air Vent

• NC - Normally Closed
• NEC - National Electric Code
• NFPA - National Fire Protection Association
• NO - Normally Open
• NPT - National Pipe Thread
• NTC - Negative Temperature Coefficient

1. OA - Outside Air
2. OAT - Outside Air Temperature
3. OP - Oil Pressure
4. ODP - Ozone Depletion Potential

• PCB - Printed Circuit Board
• PE - Pnuematic to Electric
• PID - Proportional, Integral, & Derivative
• PRV - Pressure Reducing Valve
• PSC - Permanent Split Capacitor
• PSIA - Pounds per Square Inch Absolute
• PSIG - Pounds per Square Inch Gauge
• PT - Pressure Temperature
• PTAC - Portable Terminal Air Conditioner
• PTC - Positive Temperature Coefficient
• PWM - Pulse Width Modulation

1. RA - Return Air or Reverse Acting
2. RAT - Return Air Temperature
3. RF - Return Fan
4. RH - Relative Humidity
5. RPBP - Reduced Pressure Backflow Preventer (sometimes also seen as RPZ)
6. RPM - Revolutions Per Minute
7. RTU - Roof Top Unit
8. RV - Reversing Valve

• SA - Supply Air
• SAT - Supply Air Temperature
• SCADA - Supervisory Control and Data Acquisition
• SD - Smoke Damper
• SEER - Seasonal Energy Efficiency Ratio
• SF - Service Factor or Supply Fan
• SH - Super Heat
• SMACNA - Sheet Metal and Air Conditioning Contractors National Association
• SP - Static Pressure or Set Point
• SPDT - Single Pole Double Throw
• SPST - Single Pole Single Throw
• SV - Solenoid Valve

1. TD - Temperature Difference or Time Delay
2. TDS - Total Dissolved Solids
3. TH - Thermometer in a Thermowell
4. TEV - Thermostatic Expansion Valve (sometimes also seen as TXV)
5. Ton - ton of refrigeration effect
6. TSTAT - Thermostat

• UH - Unit Heater
• UMC - Uniform Mechanical Code
• UV - Ultra-Violet or Unit Ventilator

1. VAV - Variable Air Volume
2. VFD - Variable Frequency Drive
3. VSD - Variable Speed Drive
4. VVT - Variable Volume/Temperature

• W - Watt
• WB - Wet Bulb
• WC - Water Column

          XFMR - Transformer

          ZD - Zone Damper

HVAC Definition

In air conditioning and heating the name HVAC is often used. HVAC stands for heating, ventilation, and air conditioning. Other acronyms less used to describe air conditioning and heating applications is HVACR or heating, ventilation, air conditioning, and refrigeration and HACR or heating, air conditioning and refrigeration. HVAC can be used to also describe the trade HVAC where many technicians and support personal work to install, maintain, and service HVAC equipment. Mechanical and electrical engineers and advanced level air conditioning and heating tradesman have the responsibility to design HVAC equipment and properly ensure it is installed correctly. HVAC and HVACR can include very small refrigerators, air conditioners, and heaters and HVAC can also include very large systems which maintain temperature and comfort factors in large commercial building and industrial settings.

Trade
The trade has many different types of jobs included such as service technician, installation technician, refrigeration technicians, and controls such as building automation systems (or also referred to as DDC). Modern controls systems utilize computer programs and programmable controllers to monitor the temperatures and air quality in buildings so that the occupants are comfortable and have healthy air to breath indoors.

Equipment
All equipment in an air conditioning and heating system (Heating, Ventilation, and Air Conditioning system are designed to work together to maintain comfort the buildings occupants. From residential to commercial HVAC helps keep people comfortable and healthy by maintaining good indoor air quality and comfortable temperatures.

Companies and Contractors
There are many residential HVAC companies which specialize entirely in the residential market and light commercial. These companies service, repair, and maintain HVAC comfort systems for homes and small businesses. Some of these air conditioning and heating companies also offer plumbing services as some plumbing services are similar to air conditioning and heating services. These companies service small to medium sized air conditioning and heating equipment.

There are also HVAC companies which specialize entirely in the commercial HVAC market and service large commercial HVAC systems for medium to large buildings for the comfort of the occupants and for temperature control for equipment like servers and computers. These companies service medium to large HVAC equipment.

Manufacturers
HVAC Manufacturers the produce air conditioning and heating equipment play a key role in the industry include Trane, Carrier, York, Goodman, Burnham, and McQuay. These manufacturers produce air conditioning and heating equipment such as air conditioners, gas furnaces, heat pumps, and other air conditioning and heating equipment like indoor air quality equipment.

Heating
Heating in HVAC can be any number of heating systems from gas furnaces, electric furnaces, oil furnaces, oil and gas boilers, radiant heating systems, and heat pumps. The "H" stands for heating and comprises of all of the aforementioned ways of providing heat using different methods and different types of heating systems. Heating systems include forced air systemsand hydronic hot water systems to provide heating for comfort and safety.

Ventilation
Ventilation in HVAC or the "V" describes ventilation. This can be ventilating a homeusing ductworkor ventilating a kitchen using ductwork and fans with a hood. It can also refer to combustion air or the air needed to have combustion for various heating systems. All of these various things are applicable to the "V" in HVAC. Ventilation is considered very important to the safety and health of occupants in buildings and structures and safe ventilation rates are defined in various mechanical codes to provide safe and healthy air changes to the inside of buildings and structures. Ventilation includes natural ventilation and mechanical ventilation.

Air Conditioning or AC
The "AC" refers to air conditioning and the various methods of air conditioninguse the refrigeration process for cooling air or water for conditioning and cooling the space. Air conditioners and chillers usually accomplish the job of air conditioning or the "AC" in HVAC.
Refrigeration

If the HVAC has an "R" at the end of it then the "R" stands for refrigeration. This can be applicable to residential or commercial refrigeration units including large refrigeration units for supermarkets and cold storage warehouses. From the smallest refrigeration unit all the way up to refrigerated warehouses the "R" in HVACR is applicable to this description of refrigeration.

HVACR is a thriving business not only for refrigeration systems but also for helping to keep people comfortable with warmth in the winter and cooling in the summer. It is a hardworking and necessary industry in this day and age and if you need a good job inside this industry it wouldn't hurt to look into HVAC educational opportunities for a long term HVAC career.

Chillers Applications

Some Examples of Chillers' applications

Aerospace

Air Conditioning

Analytical Equipment / Instruments

Automotive

Bakery Cooling

Batch Cooling

Brewery Cooling

C.A.T. Scan Cooling

Cold Trap Cooling

Computer Room Air Conditioning

Computers

CVO Systems

Deionized Recirculation

Diffusion Pumps

Drinking Water Fountain Cooling

Dry Cleaning Machine Cooling

EDM

Electron Microscopy

Environmental Chambers

Fiber Optics Equipment

Food

Fruit and Vegetable Washing

General Cooling Applications

General Cooling Multiple Applications

General Laboratory

Heat Exchanger

Heat Treating

Hypothermia Blankets

Ice Machine Pre-Cooling

ICP Systems

Injection Molding Cooling

Ion Etchers

Jacket Cooling

Lab Testing

Laser

Lasers (CO2, Yag)

Low Stability Cooling

Machine Cooling

Machine Tool

Medical Lasers

Metallizing

MRI

Multiple Instruments Cooling

Oil Cooling

Operating Room Air Conditioning

Optical Coating

Optical Disc

P.E.T Scan Cooling

Paint & Finishing

Photo Process Cooling

Plasma & Sputtering Systems

Plasma Cleaning / Etch Equipment / Plasma Systems

Plastics

Plating Process Cooling

Power Supplies

Proton Exchange Membrane

Solar/Photovoltaic

Spectrophotometer

Sputtering Systems

Steam Sampling

Surface Mount

Thermal Spray

Vacuum Systems

Waterjet

Welders

Welding Machine Cooling

Wet Benches

Wet Station Equipment

Winery Cooling

X-Ray Developer Cooling

X-ray Spectroscopy