commonly subjected in service. The cylinder code
color for R-12 is white.
Monochlorodifluoromethane, normally called
R-22, is a synthetic refrigerant developed for
refrigeration systems that need a low-evaporating
temperature, which explains its extensive use in
household refrigerators and window air conditioners.
R-22 is nontoxic, noncorrosive, nonflammable, and
has a boiling point of -41°F at atmospheric pressure.
R-22 can be used with reciprocating or centrifugal
compressors. Water mixes readily with R-22, so larger
amounts of desiccant are needed in the filter-driers to
dry the refrigerant. The cylinder code color for R-22 is
R-502 is an azeotropic mixture of 48.8 percent
R-22 and 51.2 percent R-115. Azeotropic refrigerants
are liquid mixtures of refrigerants that exhibit a
constant maximum and minimum boiling point. These
mixtures act as a single refrigerant. R-502 is
noncorrosive, nonflammable, practically nontoxic,
and has a boiling point of -50°F at atmospheric
This refrigerant can only be used with
reciprocating compressors. It is most often used in
refrigeration applications for commercial frozen food
equipment, such as frozen food walk-in refrigerators,
frozen food display cases, and frozen food processing
plants. The cylinder color code for R-502 is orchid.
R-134a, tetrafluoroethane, is very similar to R-12,
the major difference is that R-134a has no harmful
influence on the ozone layer of the earth's atmosphere
and is a replacement for R-12 applications.
Noncorrosive, nonflammable, and nontoxic, it has a
boiling point of -15°F at atmospheric pressure. Used
for medium-temperature applications, such as air
conditioning and commercial refrigeration, this
refrigerant is now used in automobile air-conditioners.
The cylinder color code for R-134a is light (sky) blue.
In addition to the previously mentioned
refrigerants, other less common refrigerants are used
in a variety of applications.
R-717 Ammonia (NH3)
Ammonia, R-717, is commonly used in industrial
systems. It has a boiling point of -28°F at atmospheric
pressure. This property makes it possible to have
refrigeration at temperatures considerably below zero
without using pressure below atmospheric in the
evaporator. Normally it is a colorless gas, is slightly
flammable, and, with proper portions of air, it can form
an explosive mixture, but accidents are rare. The
cylinder color code for R-717 is silver.
R-125 Pentafluoroethane (CHCF5)
Pentafluoroethane, R-125, is a blend component
used in low- and medium-temperature applications.
With a boiling point of -55.3°F at atmospheric
pressure, R-125 is nontoxic, nonflammable, and
noncorrosive. R-125 is one replacement refrigerant
All refrigerants have their own characteristics. It
is extremely important to charge a system with the
refrigerant specified. Use of an incorrect refrigerant
can lead to reduced efficiency, mechanical problems,
and dangerous conditions.
OZONE PROTECTION AND THE CLEAN
Several scientific studies conducted in the 1970s
showed that chlorine was a leading cause of holes in
the ozone. In 1987, 30 countries signed the Montreal
Protocol, which mandated the phase out of the
production, and eventual use, of all harmful CFCs. In
1990, the most significant piece of legislation affecting
the air conditioning and refrigeration industry, the
Clean Air Act, was passed. Regulated by the
Environmental Protection Agency (EPA), Title VI of
the Clean Air Act states fully halogenated refrigerants
(CFCs) will be phased out. It also calls for the phase
out of HCFCs by the year 2030. Both of these types of
refrigerants adversely affect the atmosphere, and as of
July 1992, it is illegal to discharge refrigerant to the
atmosphere. The production of R-12 was discontinued
in December 1995, and the production of R-11, R-113,
R-114, and R-115 is scheduled to be discontinued by