WD Catalog 2018

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4-3 - -
-25° 0° 25° 50° 75° 100° 125° 150°
0
25
50
75
100
125
150
175
200
LIQUID
VAPOR
SYSTEM OPERATING PRESSURE (PSI)
TYPICAL LOW
TEMPERATURE &
PRESSURE RANGE
IN EVAPORATOR
TYPICAL HIGH
TEMPERATURE &
PRESSURE RANGE
IN CONDENSER
SYSTEM OPERATING TEMPERATURES (°F)
R-12 REFRIGERANT R-134A REFRIGERANT
-25° 0° 25° 50° 75° 100° 125° 150°
0
25
50
75
100
125
150
175
200
LIQUID
VAPOR
TYPICAL LOW
TEMPERATURE &
PRESSURE RANGE
IN EVAPORATOR
TYPICAL HIGH
TEMPERATURE &
PRESSURE RANGE
IN CONDENSER
WARNING As controlled by federal law and in agreement with
other countries, the production of R-12 is being phased
out. Air conditioner systems with R-134a are appear-
ing in many vehicles. These two refrigerants must not
be mixed. This means that different equipment must
be used in the handling of each refrigerant.
The Society of Automotive Engineers (SAE) has cre-
ated certain Standards or Recommended Practices for
handling refrigerants. For example, different service
fittings are specified for R-12 and R-134a.
Combining R-12 and R-134a can result in poor cool-
ing performance, higher operating pressures and inad-
equate lubricant circulation.
Lubricants
Lubricants, like other system components, are developed for use with specific
refrigerants. Mineral oil works very well with R-12 but becomes chemically
unstable with R-134a.
Polyalkylene glycols, called PAGs, are being considered by many for use with
R-134a. In addition, a family of ester based lubricants are being given serious
consideration.
The lubricant is in the system to protect the compressor from wear and
failure. With R-134a the compressor manufacturer specifies the lubricant best
suited to its product. On new R-134a systems labeling should identify the type
and amount of lubricant.
Compressors
Figure 4-2
This graph shows the pres-
sure/temperature relation-
ship of R-12 and R-134a
inside the AC system. Re-
frigerant is a liquid on the
left (shaded) side of the
curved line. On the right
side it is a vapor or gas.