Chapter 6 Introduction to Refrigerants
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6.1.2 Environmental Impact
of Refrigerants
The impact of a refrigerant on the environment
is measured in two ways by the Environmental
Protection Agency:
• Ozone depletion potential (ODP). Ozone depletion
potential is the measurement of the ability of a
refrigerant to destroy the ozone layer. The base unit
of measurement is the refrigerant R-11, which has
an ODP of 1.0. The more harmful the refrigerant is
to the ozone layer, the higher the ODP.
• Global warming potential (GWP). Global warming
potential is a measure of the ability of a gas to
contribute to global warming over time. The baseline
gas is carbon dioxide (CO2), which has a GWP of
1.0. GWP is commonly measured over a 100-year
time period.
Figure 6-2 illustrates the ODP and GWP of differ-
ent types of refrigerants. The refrigerant R-12, which is
a CFC, has an ODP of 1.0 and a GWP of 10,900!
Ozone Depletion Potential (ODP)
To provide a clearer perspective on the amount
of ozone depletion caused by certain substances, a
numeric value has been assigned to each refrigerant
and is referred to as its ozone depletion potential
(ODP). The ODP scale has a minimum value of zero
and compares the destructive potential of different
chemicals to the destructive potential of R-11, which is
1 on the ODP scale. A refrigerant that is half as destruc-
tive as R-11 would have an ODP value of 0.5. A chemi-
cal that is five times as destructive as R-11 would have
an ODP value of 5. The higher a refrigerant’s ODP is,
the greater the risk for ozone layer depletion.
As illustrated by the chart in Figure 6-2, the three
primary types of refrigerants vary greatly in ODP. CFC
refrigerants receive a high ODP rating, HCFC refrig-
erants possess a low ODP, and HFC refrigerants have
no ODP.
Global Warming Potential (GWP)
As mentioned previously, the ozone layer helps to
maintain stable temperatures on the earth. Scientists
have concluded that some refrigerants contribute to
global warming. Global warming is caused by long-
wave radiation from the sun that becomes trapped
within the earth’s atmosphere. This trapped radiation
slowly heats the earth’s surface.
Each refrigerant is assigned a number that expresses
its global warming potential (GWP). The GWP rating
is based on the ratio of a substance’s warming effect
compared to the warming effect of carbon dioxide. The
higher the GWP is, the greater the risk of environmen-
tal damage.
6.2 Classifying Refrigerants
Most refrigerants used today are divided into four
different chemical categories:
• Chlorofluorocarbons (CFCs).
• Hydrochlorofluorocarbons (HCFCs).
• Hydrofluorocarbons (HFCs).
• Refrigerant blends (azeotropic and zeotropic).
6.2.1 CFC Refrigerants
Chlorofluorocarbons (CFCs) were the first
halogen-based refrigerants developed over eighty
years ago. Besides being used as refrigerants, CFCs
have also been used as blowing agents for the manu-
facture of insulation and packaging. CFCs are com-
posed of chlorine, fluorine, and carbon. Common
CFC refrigerants include R-11 and R-12.
When CFCs are vented into the atmosphere, their
chlorine atoms attach to the oxygen atoms in ozone
molecules and break the ozone molecules apart. Acting
as a catalyst, the chlorine makes three normal oxygen
molecules from two ozone molecules. Each chlorine
atom can break apart as many as 100,000 ozone mol-
ecules before it is neutralized through other chemical
reactions. This results in the reduction of ozone and an
increase in ultraviolet radiation reaching Earth.
CFCs have high ODPs and are one of the major
causes of ozone depletion. By international agreement,
they have not been manufactured in developed coun-
tries since the end of 1995. However, CFCs may still
be found in some air conditioning and refrigeration
equipment produced before 1995.
Goodheart-Willcox Publisher
Figure 6-2. Table showing the global warming potential and
ozone depletion potential for different types of refrigerants.
Environmental Properties of Refrigerants
ASHRAE
Refrigerant #
Type
ODP
(Ozone
Depletion
Potential)
GWP
(Global
Warming
Potential)
R-12 CFC 1 10,900
R-22 HCFC 0.05 1,810
R-123 HCFC 0.02 77
R-134a HFC 0 1,430
R-407C HFC 0 1,774
R-410A HFC 0 2,088
R-1234yf HFO 0 4