Service Procedure
40
©2007 Viking Preferred Service
Comparison of CFC12 and HFC134a Properties
Properties/Characteristics CFC12
HFC134a
Ozone Depletion Potential (ODP)
1.0*
0.0*
Global Warming Potential (GPW)
3.2*
0.27*
Molecular weight
121
102
Boiling point at 1 atmosphere
-22°F
(-30°C)
-15°F
(-126°C)
Vapor pressure at 77°F (25°C)
80 psig
82 psig
Liquid density at 77°F (25°C)
82 lb/ft
3
75
lb/ft
3
Flammability No
No
High-side system operating
Pressure at 65°F (18°C)
HFC134a approximately
3 psig higher than CFC12
Low-side system operating
Pressure at 65°F (18°C)
HFC134a approximately
2 psig lower than CFC12
CAUTION
To minimize contamination, exercise extreme care when
servicing HFC134A sealed systems.
No trace of other refrigerants is allowed in HFC134a
systems. Chlorinated molecules in other refrigerants
such as CFC12, etc. will lead to capillary tube plugging.
Ester oil is used in HFC134a systems. Do not use
mineral oil. HFC134a and mineral oils cannot be mixed.
If mineral oils were used in HFC134a systems, lubricant
would not return to compressor and would cause early
compressor failure. If significant amount of oil has been
lost from compressor, replace oil rather than adding oil.
Ester oils used in HFC134a systems are so hydroscopic
that by the time an inadequate system performance is
detected, oil will be saturated with moisture.
CFC12 has much higher tolerance to system processing
materials, such as drawing compounds, rust inhibitors,
and cleaning compounds, than HFC134a. Such
materials are not soluble in HFC134a systems. If
materials were to be washed from system surfaces by
ester oils, they could accumulate and eventually plug
capillary tube.
Care must be taken to minimize moisture entering
HFC134a system. Do not leave compressor or system
open to atmosphere for more than 10 minutes.
Excessive moisture in HFC134a system will react with
compressor oil and generate acid.
Compressor must be replaced when performing low side
leak repair.
Drier filter must always be replaced with service drier
filter.
IMPORTANT:
Unbrazing drier filter from tubing will
drive moisture from desiccant and into
system, causing acids to form. Do not
unbraze filter drier from tubing. If CFC12
service drier was installed in HFC134A
system, drier could overload due to
excessive moisture.
HFC134a compatible copper tubing
must be used when replacing tubing.
Avoid system contamination when
flaring, swagging, or cutting refrigeration
tubing.
Brazing
CAUTION
To avoid risk of personal injury or property damage, take
necessary precautions against high temperatures
required for brazing.
Satisfactory results require cleanliness, experience, and
use of proper materials and equipment.
Connections to be brazed must be properly sized, free of
rough edges, and clean.
Generally accepted brazing materials are:
Copper to copper joints:
SIL-FOS (alloy of 15 percent silver, 80 percent copper,
and 5 percent phosphorous). Use without flux.
Recommended brazing temperature is approximately
1400°F. Do not use for copper to steel connection.
Copper to steel joints:
SILVER SOLDER (alloy of 30 percent silver, 38 percent
copper, 32 percent zinc). Use with fluoride based flux.
Recommended brazing temperature is approximately
1200°F.
Steel to steel joints:
SILVER SOLDER (see copper to steel joints).
Brass to copper joints:
SILVER SOLDER (see copper to steel joints).
Brass to steel joints:
SILVER SOLDER (see copper to steel joints).
