41
R-134a SERVICE INFORMATION
NOTICE: Instructions given here are furnished as a guide. Persons attempting to use these instructions to make
repairs to the sealed refrigeration system should have a working knowledge of refrigeration and previous training
on sealed system repair.
VERIFY REFRIGERANT TYPE IN THE SYSTEM
CAUTION: R-134a and R-12 are completely
incompatible. Before starting any sealed
system repair, it is extremely important to
check serial plate of product to verify the type
of refrigerant in the system.
Dedicated Equipment
R-134a must not be mixed with other types of refrigerants.
R-134a must be recovered in dedicated and properly
identified recovery bags and tanks.
It will be necessary to check with the manufacturer of
your recovery equipment to determine R-134a
compatibility. Some recovery equipment manufacturers
have changeover instructions for switching between
refrigerant types. Protect yourself and your equipment
by following all manufacturer guidelines.
Also, ensure that your refrigeration hoses are specified
for use with R-134a refrigerant. Research has shown
that compounds in standard refrigeration hoses may
enter sealed systems and ultimately restrict the cap
tube in an R-134a system.
R-134a REFRIGERATION SYSTEMS
The sealed refrigeration system will consist of the same
basic components being utilized in the R-12 systems.
There is a 10% to 15% discharge pressure increase
using R-134a, with a 5% to 10% decrease in suction
pressure when compared to the same product with an
R-12 system operating at 90°F (32°C) ambient
temperature conditions. Lower suction pressures result
from the lower density of R-134a refrigerant which
effects refrigerant flow rate. R-134a systems commonly
operate in a 1”-2” vacuum on the suction side.
Products using R-134a refrigerant will generally have a
longer capillary tube to maintain a similar flow rate and
some models will have a larger condenser to reduce the
discharge pressures and lower start-up sound
transmission.
MISCIBILITY OF R-134a AND ESTER OIL
A special synthetic oil known as Ester oil is used as a
lubricant in refrigeration systems operating on R-134a.
Ester oils are produced from alcohols and fatty acids
and are available in several different variants. Ester oils
have a pleasant aroma reminiscent of fruit.
Ester oils generally include various types of additives for
improving certain properties such as viscosity,
temperature sensitivity, etc. These additives are often
aggressive, and skin contact with Ester oils should
therefore be avoided.
One of the most important requirements made on a
refrigerant system is that the oil mix with the refrigerant.
Since mineral oil and ordinary synthetic oil DO NOT mix
with R-134a, Ester oil is used for lubrication. Ester oil
dissolves in R-134a.
Ester oil is broken down by chlorine and cannot be used
with R-12 (R-12 contains chlorine) or any other compound
containing chlorine. Therefore, R-134a refrigeration
systems have virtually no tolerance for chlorine
molecules from CFC refrigerants (R-134a is an HFC and
contains no chlorine).
CAUTION: During R-134a service, it is
extremely important to avoid using
equipment that may contain residual amounts
of mineral oil, CFC’s or HCFC’s which could
enter and contaminate the sealed system.
For example, hoses that were used for a refrigeration
system operating on R-12 may contain small quantities
of mineral oil which can block the capillary tube in a
system operating on R-134a. As little as one milligram
may be sufficient to cause a blockage. In addition,
sealed system components that have been used with
CFC systems must not be used with R-134a systems.
These components may contain residual amounts of
refrigerant and oil which could damage an R-134a
system.
At the earliest stage of development work on R-134a,
tests were carried out on a different type of synthetic oil
known as Poly-Alkaline Glycol (PAG). This oil is also
used in certain air conditioning systems for cars. PAG
and Ester oil DO NOT mix with one another. Service
equipment used for R-134a / Ester oil must not come into
contact with PAG.
To Next Page
Loading...
Need help?
General
