Electrolux Built-in 42" Service Manual page 19

Water in the refrigeration system
Even in very small quantities, water in any refrigera-
tion 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 hydroscopic (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 adaptors 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.
V A C U U
V a c u u m
M
n I c h e s H . g
2 8 9 . 4 0
2 9 5 . 3 0
2 9 8 . 3 2
2 9 8 . 8 2
2 9 9 . 0 1
2 9 9 . 1 5
2 9 9 . 1 7
2 9 9 . 1 9
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
pumping at a lower pressure so a lower ultimate vacuum
can be achieved (See 2-Stage Vacuum Pump, Figure E3).
M C H A R T
B o l i n i g P i o t n
c i o r n s
f o W t a r e F °
2 5 0 0 0 7 7 9 .
1 0 0 0 0 5 2 0 .
4 6 0 0 3 2 0 .
1 0 0 0 1 0 .
5 0 0 1 - 1 2 .
1 5 0 3 - 2 8 .
1 0 0 3 - 8 2 .
5 0 4 - 9 0 .
second stage begins
2-Stage Vacuum Pump
Figure
Vacuum pump maintenance
It is absolutely essential to maintain your vacuum
pump according to the manufacturer's instructions
including required oil changes at the recommended
intervals. Vacuum pump oil should always be changed
after evacuating a contaminated system. Vacuum pump
performance should be checked periodically with a micron
gauge.
Vacuum pump suppliers may or may not recommend
changing the vacuum pump oil to the same type that's in
the system being evacuated. Some manufacturers may
recommend a vacuum pump that's dedicated to R-134a
systems.
Robinair has stated that their current and
discontinued vacuum pump models, using mineral oil
currently specified for use in their vacuum pumps, can be
used to evacuate R-134a/Ester oil systems. Robinair also
states that it is acceptable to alternate between evacuating
R-12/mineral oil and R-134a/Ester oil systems without
adversely effecting the vacuum pump's performance.
For other brands of vacuum pumps, check with the
manufacturer for restrictions and guidelines when using
with R-134a.
CAUTION: If you use a vacuum pump with
mineral oil to evacuate an R-134a system, it
is ABSOLUTELY ESSENTIAL to have a shut-
off valve between pump and your manifold
gauge set as shown in Figure E4. The hand
valve must be closed during all times when
vacuum pump is not operating. This will
prevent migration of mineral oil vapor into
R134a/Ester oil system. If vacuum pump
should stop during evacuation for any reason,
the hand pump shut-off valve must be closed
immediately.
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