LG gr-392 Service Manual Download Page 3

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AIR RECHARGING IN COMPRESSOR

Test the refrigeration system connecting it electrically before
refilling operation. It is necessary to ascertain the function
of the motor-compressor and identify the defects
immediately. If the defects have been found, empty the old
system of eventual R-12(R134a) residue by breaking off the
end of the extension piece at its narrow point. (Figure 1)
Replace the filter and any damaged components. Unsolder
and pull off the piece remaining inside the service tube and
then attach an extension completely with male Hansen and
last, solder it to the same tube again. (Figure 2)

It is necessary to execute the soldering operation with
valve open so that the fumes caused by oil residue can
come out freely without blowholes between two tubes
during heating the point to be soldered.
The extension fitted with the male Hansen is connected to
the female fitting of the vacuum pump tube. (Figure 3)

Air evacuating from the system begins so soon as the
pump starts. The refrigeration system must be kept under
vacuum until the reading on the low-pressure gauge
indicates vacuum (0 absolute, -1 atm., -760 mm hg) in any
case it is advisable to keep the pump running for about 30
minutes. (Figure 3)
In case that a considerable leakage occurs and to stop the
vacuum pump will be necessary and add a small quantity
of Freon to the system, if vacuum should not be obtained
(pressure gauge can't fall to 1 atmosphere), start the
refrigeration unit and find the leakage with the special leak-
finder. When the defective soldering point is visible, re-do it
after opening the extension tube valve and reestablishing
the normal outside pressure inside the group.
Because the melted alloy is sucked into the tubes and
block them, the pressure must be rebalanced when
vacuum is in the system in soldering. As soon as the

vacuum operation is over, add the quantity in grams of
R-12(R134a) to the refrigerant system. Remember that
every system has an exact quantity of R-12(R134a) with a
tolerance of ±5 grams that can be added. (Figure 4)

Before performing this operation (if the vacuum pump and
refilling cylinder are connected), make sure that the valve
placed between the vacuum pump and refilling tube are
closed to keep the Freon for adding to the system. (Figure 5)

In addition, check the graduated scale on the cylinder for
the quantity of R-12(R134a) to be added, for example, if we
have 750 grams of Freon in the cylinder and must add 165
grams to the group, this amount will be reached when
R-12(R134a) has dropped to 585 grams, remembering that
the indicator shows a lower limit of meniscus. Do this after
choosing the scale corresponding to the gas pressure
different scales reported as the same gas pressure
indicated by the pressure gauge on the top of the column.
To make R-12(R134a) flow into the system, open the valve
placed at the base of the cylinder and connected to the
filling tube. The amount of Freon cannot be added to the
system all at once because it may cause a blocking of motor-
compressor. Therefore, proceed by adding original quantity
of about 20-30 grams and close the valve immediately.
The pressure rises and the motor-compressor must start,
sucking the gas and making the pressure go down again.
Regulate the valve again, maintaining the same manner
until reaching to the quantity of R-12(R134a) established
for the system being charged. When the system is running,
the suction pressure must be stabilized between 0.30 to
0.6(0.10 to 0.4) atmosphere.