Electrolux EILFU17GS, Technical & Service Manual

Page: 35 / 96

4-13
R Re effrriig ge erra attiio on n S Sy ys stte em m
To achieve the required 29.9 inch (500 micron)
vacuum, a properly maintained two-stage vacuum
pump in good condition is required. A two stage
pump can reach a deeper vacuum than a single
stage because the exhaust from the first pumping
stage is discharged into the second pumping
stage. This means the second stage begins
pumping at a lower pressure so a lower ultimate
vacuum can be achieved.
VACUUM CHART
Vacuum
Inche s Hg.
Micron s
Boiling Point
of Water °F
28.940 25000 77.9
29.530 10000 52.0
29.832 4600 32.0
29.882 1000 1.0
29.901 500 -11.2
29.915 150 -32.8
29.917 100 -38.2
29.919 50 -49.0
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.
W Wa atte err IIn n T Th he e R Re effrriig ge erra attiio on n S Sy ys stte em m
Even in very small quantities, water in any refriger-
ation system can cause the following problems:
• Ice plugs in capillary tubes.
• Copper plating in compressor.
• Reactions with organic materials in systems.
• Corrosion of metals.
R-134a and Ester oil will aggravate the problem of
water in the refrigeration system. Ester oil may
react with water vapor and is hygroscopic (it will
absorb water if it comes in contact with humid air).
Water is also more soluble in R-134a than R-12.
To minimize the water content whenever service
work is performed, the refrigeration system should
always be thoroughly evacuated through process
tube adapters on both the high and low sides of
the system. Evacuation must be for a minimum of
30 minutes to at least a 29.9 inch (500 micron)
vacuum.