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This article describes the properties of common and historic air conditioning refrigerants. We combine U.S. EPA information with supplemental data and descriptions of refrigerants, refrigerant replacement options for R12 and R22, and their basic data.

Air conditioning refrigerants and agents to transfer heat from one place to another have been in use for a long time and include Ammonia, Sulfur Dioxide, Hydrocarbons like methane, methyl chloride, and methylene chloride, and safer (inert gas) HFCs like R11 (common in older refrigerators and some air conditioners) and R22 (common in older cooling equipment. Since the realization that HFC's contribute to greenhouse gas problems in the environment, R11 and R22 have been discontinued and are being replaced with alternatives including R-410A (GENETRON AZ-20, SUVA 410A, and Puron), R-134A R-407C.

See REFRIGERANT LEAK REPAIR see PRESSURE READINGS, COMPRESSOR, and A/C REFRIGERANT LEAK DETECTION for more details.

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Properties of Various Air Conditioning and Cooling Refrigerants

• Ammonia is the oldest-known refrigerant. (Ammonia can generate cooling by simple mechanical movement). Ammonia vapor can be flammable, explosive, and toxic. Ammonia is lighter than air (so less likely to accumulate at a dangerous level near the floor). Ammonia is still used as a refrigerant in some large refrigeration systems.
  
  
• Sulphur dioxide SO₂ is obsolete and would be unusual to encounter except in very old cooling equipment. SO₂ is not flammable nor explosive but with moisture is very corrosive and can injure plants. If you have refrigeration equipment using SO₂ you should junk it - few or no service people will try to service or fix this equipment.
  
  
• Hydrocarbons such as methane CH₄, isobutane C₄H₁₀, and propane C₃H₈ are often used as fuels and sold as bottled gas. Methyl chloride CH₃CL has also been used as has methylene chloride CH₂CL₂. These halogenated hydrocarbons are less flammable; Carrene No.1 was a popular trade product version of methylene chloride (the safest of these).

• Freon & Genetron: Chemists also tried using carbon tetrachloride CCL₄ as a refrigerant by adding two chlorine atoms to produce CCL₂F₂ which founded the "R" refrigerant family R12 (by convention in a white canister) and R22 (by convention green canisters or the antique green-labeled canister shown at left).
  
  R-12 refrigerant has a boiling point of -21degF at 1ATM of pressure (sea level). And R12 has the cute property of being at 70 psi when at 70 degF temperature. Our photo at page top shows an old R-12 refrigerant canister and our air conditioning compressor charging and test gauge set.
  
  R-14 refrigerant (automotive & other uses such as in the semiconductor industry as Tetrafluoromethane ) has a boiling point of -128 C and a latent heat of vaporization (1.013 bar at boiling point) = 135.7 kJ/kg
  
  R-22 refrigerant: Our photo (left) shows an antique R-22 refrigerant dispensing canister. R22 has the not quite as cute property of being at 122 psi when at a temperature of 70 degF.
  
  These HCFC or "CFC" refrigerants were very safe (non combustible, non-toxic to humans except as an oxygen displacer) and were the most widely used until their effects in the atmosphere were understood as a serious environmental problem. The 1987 Montreal Protocol which banned their use is discussed below.
  
  
• R-410, R-134, R134A, R407 R407C, Modern refrigerants replacing the original "R" Freon series include R-410A (GENETRON AZ-20, SUVA 410A, and Puron), R-134A R-407C. These new gases have wide use. For example, the refrigerant gas R-134A is used in medications such as propellant in bronchiodialators for asthmatics like Xopenex HFA (TM).
  
  Modern refrigerants are sold in canisters ranging in size including 10lb, 15lb, 30lb and 100lb, typically at a cost per pound for liquid refrigerant. These canisters are not normally intended to be refilled, and you should not return used refrigerant gases to them either, as you risk contaminating the new refrigerant with moisture or debris.
  
  
• Water as a refrigerant was used and continues to be used to effect heat transfers in cooling tower type air conditioning systems and in "swamp coolers" which work effectively where ambient humidity is low enough to produce a good evaporation rate, such as in the American southwest. (Concerns for bacterial hazards such as Legionella occur in these systems and are discussed at CLEANING A/C EQUIPMENT

DISCLAIMER: EPA [and this website reproducing this public-domain article] seeks to promote energy efficiency and the safe use of ozone- friendly substances, and does not endorse any particular company or its products.

Safety Warnings & Other Caveats about Using Refrigerant Liquids or Gases & When Servicing Refrigeration Equipment

Watch out: any refrigerant gas and gas container, including the small refrigerant canisters sold for automotive use in charging automobile or truck air conditioners can be dangerous if not properly handled.

Liquid refrigerant can injure an eye and can also cause frostbite. You should cover refrigerant lines or connectors or valves when opening them so that if liquid refrigerant escapes it is controlled. And on at least some refrigerant containers such as the automotive maintenance canisters you'll see warnings about the need for eye protection and other protective measures.

Also some refrigerant gases form highly toxic phosgene gas if released across an open flame, so if a flame is present near where refrigerant gases are being used for service be sure there is good fresh air ventilation.

Refrigerant Gas Asphyxiation hazards: Modern refrigerant gases are heavier than air as well as being odorless and colorless. The gases themselves, such as the Freon family, are not toxic and not explosive. But because the gases are heavier than air, if you were so foolish as to release a sufficient volume of gas into an enclosed space or even a low-lying outdoor area where there is no wind or indoors no ventilation, you could become asphyxiated with little or no warning.

Do not mix refrigerant gases. Each refrigerant gas has its own unique properties. If you were to mix gases within a refrigeration system the properties of the mixture would be unpredictable, making it impossible to properly adjust and operat the equipment.

Do not arbitrarily substitute refrigerant gases by charging refrigeration equipment with a gas other than the one for which it is labeled, for the same reason as above. We discuss replacement refrigerants below.,

Background: Ban on Production and Imports of Ozone-Depleting Refrigerants

In 1987 the Montreal Protocol, an international environmental agreement, established requirements that began the worldwide phase out of ozone-depleting CFCs (chlorofluorocarbons). These requirements were later modified, leading to the phase out in 1996 of CFC production in all developed nations. In addition, a 1992 amendment to the Montreal Protocol established a schedule for the phase out of HCFCs (hydrochlorofluorocarbons). HCFCs are substantially less damaging to the ozone layer than CFCs, but still contain ozone-destroying chlorine. The Montreal Protocol as amended is carried out in the U.S. through Title VI of the Clean Air Act, which is implemented by EPA.

An HCFC known as R-22 has been the refrigerant of choice for residential heat pump and air-conditioning systems for more than four decades. Unfortunately for the environment, releases of R-22 that result from system leaks contribute to ozone depletion. In addition, the manufacture of R-22 results in a by-product that contributes significantly to global warming.

As the manufacture of R-22 is phased out over the coming years as part of the agreement to end production of HCFCs, manufacturers of residential air conditioning systems are beginning to offer equipment that uses ozone-friendly refrigerants. Many homeowners may be misinformed about how much longer R-22 will be available to service their central A/C systems and heat pumps. This fact sheet provides information about the transition away from R-22, the future availability of R-22, and the new refrigerants that are replacing R-22. This document also assists consumers in deciding what to consider when purchasing a new A/C system or heat pump, or when having an existing system repaired.

Phase out Schedule for HCFCs used in Air Conditioning Equipment, Including R-22

Under the terms of the Montreal Protocol, the U.S. agreed to meet certain obligations by specific dates that will affect the residential heat pump and air-conditioning industry:

January 1, 2004 HCFC Refrigerant Reduction Target

In accordance with the terms of the Montreal Protocol, the amount of all HCFCs that can be produced nationwide must be reduced by 35% by 2004. In order to achieve this goal, the U.S. is ceasing production of HCFC-141b, the most ozone-damaging of this class of chemicals, on January 1, 2003. This production ban will greatly reduce nationwide use of HCFCs as a group, making it likely that the 2004 deadline will have a minimal effect on R-22 supplies.

January 1, 2010 HCFC Refrigerant Reduction Target

After 2010, chemical manufacturers may still produce R-22 to service existing equipment, but not for use in new equipment. As a result, heating, ventilation and air-conditioning (HVAC) system manufacturers will only be able to use pre-existing supplies of R-22 to produce new air conditioners and heat pumps. These existing supplies would include R-22 recovered from existing equipment and recycled.

January 1, 2020 HCFC Refrigerant Reduction Target

Use of existing refrigerant, including refrigerant that has been recovered and recycled, will be allowed beyond 2020 to service existing systems, but chemical manufacturers will no longer be able to produce R-22 to service existing air conditioners and heat pumps.

For more information about this phase out, see fact sheets about the HCFC Phase out Schedule and Frequently Asked Questions on the HCFC Phase out

What Does the R-22 Phase out Mean for Consumers?

Availability of R-22

The Clean Air Act does not allow any refrigerant to be vented into the atmosphere during installation, service, or retirement of equipment. Therefore, R-22 must be recovered and recycled (for reuse in the same system), reclaimed (reprocessed to the same purity levels as new R-22), or destroyed. After 2020, the servicing of R-22-based systems will rely on recycled refrigerants.

It is expected that reclamation and recycling will ensure that existing supplies of R-22 will last longer and be available to service a greater number of systems. As noted above, chemical manufacturers will be able to produce R-22 for use in new A/C equipment until 2010, and they can continue production of R-22 until 2020 for use in servicing that equipment. Given this schedule, the transition away from R-22 to the use of ozone-friendly refrigerants should be smooth. For the next 20 years or more, R-22 should continue to be available for all systems that require R-22 for servicing.

Cost of R-22

While consumers should be aware that prices of R-22 may increase as supplies dwindle over the next 20 or 30 years, EPA believes that consumers are not likely to be subjected to major price increases within a short time period. Although there is no guarantee that service costs of R-22 will not increase, the lengthy phase out period for R-22 means that market conditions should not be greatly affected by the volatility and resulting refrigerant price hikes that have characterized the phase out of R-12, the refrigerant used in automotive air-conditioning systems.

Alternatives to R-22 in Residential Air Conditioning

As R-22 is gradually phased out, non-ozone-depleting alternative refrigerants are being introduced. Under the Clean Air Act, EPA reviews alternatives to ozone-depleting substances like R-22 in order to evaluate their effects on human health and the environment.

EPA has reviewed several of these alternatives to R-22 and has compiled a list of substitutes that EPA has determined are acceptable. One of these substitutes is R-410A, a blend of hydrofluorocarbons (HFCs), substances that do not contribute to depletion of the ozone layer, but, like R-22, contribute to global warming. R-410A is manufactured and sold under various trade names, including GENETRON AZ-20(R), SUVA 410A(R), and Puron(R).

Additional refrigerants on the list of acceptable substitutes include R-134a and R-407C. These two refrigerants are not yet available for residential applications in the U.S., but are commonly found in residential A/C systems and heat pumps in Europe. EPA will continue to review new non-ozone-depleting refrigerants as they are developed.

Replacements for R12 Refrigerants

There are replacement gases for certain of the now banned refrigerants discussed in this article. Quoting Zeller 1998 [1]

Suva MP39 and Suva MP66 are a mixture of 3 components, HCFC-22, HFC- 152A and ACFH-124, which have been created to replace CFC-12 in medium temperatures. The majority of compressors for CFC-12 can adapt to the use of MP39 and MP66 easily and economically. This allows for the equipment already installed to continue in service during their lifetime.

The two new refrigerants demonstrate many properties which have been im- proved towards the ozone and the environment, in comparison with CFC-12.

The MP mixtures are compatible with the majority of the materials used for the construction of the CFC systems. The composition of each mixture has been selected to be compared with the eciencies of CFC-12 in specied applications, in energetic capacity and eciency. This gives as a result a minimal mechanical interruption when CFC-12 is replaced with MP66 or MP39. Other refrigerants like the HCFC-22 or the HCFC-134A, require an extensive mechanical intervention in the systems when they are replaced, which will at times be expensive.

MP66 and MP39 give the user the chance to change refrigerants without spend- ing much in modications to the CFC-12 systems. CFC-134A can also be used in evaporation temperatures lower than -7 C and 20 F but can demonstrate less capacity in these temperatures than the CFC-12, to cover the whole range of temperatures of the CFC-12, we also have the MP66 and the MP39. [1]

 

Servicing existing A/C units

Existing units using R-22 can continue to be serviced with R-22. There is no EPA requirement to change or convert R-22 units for use with a non-ozone-depleting substitute refrigerant. In addition, the new substitute refrigerants cannot be used without making some changes to system components. As a result, service technicians who repair leaks to the system will continue to charge R-22 into the system as part of that repair.

Installing new Air Conditioning units

The transition away from ozone-depleting R-22 to systems that rely on replacement refrigerants like R-410A has required redesign of heat pump and air conditioning systems. New systems incorporate compressors and other components specifically designed for use with specific replacement refrigerants. With these significant product and production process changes, testing and training must also change. Consumers should be aware that dealers of systems that use substitute refrigerants should be schooled in installation and service techniques required for use of that substitute refrigerant.

Along with prohibiting the production of ozone-depleting refrigerants, the Clean Air Act also mandates the use of common sense in handling refrigerants. By containing and using refrigerants responsibly -- that is, by recovering, recycling, and reclaiming, and by reducing leaks -- their ozone depletion and global warming consequences are minimized. The Clean Air Act outlines specific refrigerant containment and management practices for HVAC manufacturers, distributors, dealers and technicians. Properly installed home comfort systems rarely develop refrigerant leaks, and with proper servicing, a system using R-22, R-410A or another refrigerant will minimize its impact on the environment. While EPA does not mandate repairing or replacing small systems because of leaks, system leaks can not only harm the environment, but also result in increased maintenance costs.

One important thing a homeowner can do for the environment, regardless of the refrigerant used, is to select a reputable dealer that employs service technicians who are EPA-certified to handle refrigerants. Technicians often call this certification "Section 608 certification," referring to the part of the Clean Air Act that requires minimizing releases of ozone-depleting chemicals from HVAC equipment.

A Common Sense Approach To Purchasing New Air Conditioning Systems

Another important thing a homeowner can do for the environment is to purchase a highly energy-efficient system. Energy-efficient systems result in cost savings for the homeowner. Today's best air conditioners use much less energy to produce the same amount of cooling as air conditioners made in the mid-1970s.

Even if your air conditioner is only 10 years old, you may save significantly on your cooling energy costs by replacing it with a newer, more efficient model. Products with EPA's Energy Star(R) label can save homeowners 10% to 40% on their heating and cooling bills every year. These products are made by most major manufacturers and have the same features as standard products but also incorporate energy saving technology. Both R-22 and R-410A systems may have the Energy Star(R) label. Equipment that displays the Energy Star(R) label must have a minimum seasonal energy efficiency ratio (SEER). The higher the SEER specification, the more efficient the equipment.

You should consider energy efficiency, along with performance, reliability and cost, in making your decision. And don't forget that when purchasing a new system, you can also speed the transition away from ozone-depleting R-22 by choosing a system that uses ozone-friendly refrigerants.

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• [1] Commercial Air Conditioning Systems, Julio O. Zeller, May 1, 1998, University of Notre Dame, web search 07/27/2011, original source: http://www.nd.edu/~msen/Teaching/DirStudies/AirConditioning.pdf
• [2] Theoretical Analysis of Replacement Refrigerants for R22 for Residential Use, U.S. EPA, January 1992, EPA/400/191/041, web search 07/27/2011, original source: National Service Center for Environmental Publications (NSCEP), http://nepis.epa.gov/

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.

• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
• Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
• Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
• Asbestos HVAC Ducts and Flues field identification photos and guide
• Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
• ...