Thermo King 002008, Manual

Page: 80 / 155

Refrigeration Maintenance
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5. Observe the receiver tank sight glass and the
unit’s discharge pressure.
6. By the time the discharge pressure drops
approximately 50 psig (345 kPa) the ball in
the receiver tank sight glass should begin to
move and the liquid level should drop.
a. When discharge pressure stabilizes, the
ball and liquid level will rise.
b. If the ball will not begin to move or the
liquid level will not drop, the unit most
likely has an overcharge of refrigerant.
The refrigerant level should be adjusted.
Adjusting Refrigerant Level
1. Stop the unit and remove some refrigerant
with an approved refrigerant recovery device.
2. Perform a refrigerant level check and repeat
the overcharge test.
3. If the liquid level is low, add refrigerant as
follows:
a. Connect a refrigerant tank to the gauge
manifold service line and purge the line.
b. Mid seat the suction service valve.
c. Set the refrigerant tank for liquid removal
and open the hand valve.
d. Operate the unit in high speed with all
evaporators in cool.
e. Observe the suction pressure and slowly
open the gauge manifold low pressure
hand valve to allow liquid refrigerant to
flow into the suction service valve.
f. Control the liquid flow so the suction
pressure increases approximately 20 psig
(138 kPa).
g. Maintain a discharge pressure of at least
325 to 400 psig (2241 to 2758 kPa) while
adding refrigerant.
h. Close the hand valve on the refrigerant
tank when liquid appears in the receiver
sight glass.
4. Repeat the overcharge test.
5. Remove the gauge manifold set and cap all
service ports and valve stems when the
refrigerant level is correct.
Moisture Indicating Sight Glass
The receiver tank is equipped with a moisture
indicating sight glass. The outer edge of the sight
glass has a colored ring approximately 0.1 in.
(2.5 mm) thick. The color of the ring indicates the
moisture content of the refrigerant, but it may not
be completely reliable.
• Green = Dry
• Chartreuse = Caution
• Yellow = Wet
A system has to run for at least 15 minutes to
change the color of the indicator ring after the
moisture content of the system has been changed.
For example, evacuating a system to remove the
moisture will not change the color of the indicator
ring until the system has been recharged and then
operated for at least 15 minutes.
Refrigerant Leaks
Use a reliable leak detector that is suitable for
R-404A to leak test the refrigeration system.
Inspect for signs of oil leakage which is the first
sign of a leak in the refrigeration system.
1. Floating Ball
2. Colored Ring
Figure 53: Moisture Indicating Sight Glass
AEA672
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