Thermo King T-1080S, Maintenance Manual

Page: 128 / 191

Refrigeration Service Procedures
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in the receiver tank sight glass, the unit may
be low on refrigerant. Perform a Controlled
Check.
NOTE: If the ball floats, there is sufficient
refrigerant in the unit for that load at that
particular box temperature. This test does
not determine if the unit contains a full
charge of refrigerant.
Checking Compressor Oil
The compressor oil should be checked when there
is evidence of oil loss (oil leaks) or when
components in the refrigeration system have been
removed for service or replacement. The oil level
in the compressor oil sight glass should be 1/4 to
3/4 full.
To check compressor oil level with an ambient air
temperature above 50 F (10 C):
Install a gauge manifold.
Operate the unit on high speed cool with a 10 psig
(69 kPa) minimum suction pressure and 185 psig
(1275 kPa) minimum discharge pressure for 15
minutes or more.
After the unit has maintained the above conditions
for 15 minutes, observe the oil level. The oil
should be 1/4 to 3/4 up in the sight glass.
To check compressor oil level with an ambient air
temperature below 50 F (10 C):
Run the unit through a complete Defrost cycle.
After completing the Defrost cycle, run the unit
on Cool for ten minutes. Observe the oil level.
The oil should be 1/4 to 3/4 up in the sight glass.
If the evaporator temperature is above 32 F (0 C),
it will be necessary to force defrost. To force
defrost, use the relay board test.
If the box is empty, you can run the unit on the
Heat cycle instead of the Defrost cycle.
NOTE: Use refrigeration compressor oil ONLY.
R-404A systems use a special Ester oil
(P/N 203-516). Required for Scroll compressors.
Oil can be added to the compressor through the
Schrader valve on the suction adapter while the
unit is running. Take precautions to prevent
contaminants from entering the system while
adding oil. Also see “Scroll Compressor Oil
Change”.
Refrigeration System Checks
1. Attach a gauge manifold to the suction service
valve and the discharge service port. Attach an
additional low pressure gauge to the suction
access port located in the suction line near the
accumulator inlet. Low loss fittings must be
used on the hoses connected to the discharge
service port and the suction access port.
2. Check the system pressures and the refrigerant
flow in heat and cool. The suction and
discharge pressures should be within the
normal ranges for a standard unit. Check the
temperatures of the refrigeration lines by hand
to check the refrigerant flow. See the
individual test for a component if you suspect
it is not functioning properly.
3. Run the unit in high speed cool until the
system pressures stabilize.
4. Note the discharge pressure on the high
pressure gauge.
5. Check the compressor by covering the
condenser and checking the discharge
pressure. The compressor should be able to
increase the discharge pressure by at least 100
psig (689 kPa) or to 375 psig (2586 kPa). The
1. Compressor Oil Sight Glass Location
Figure 217: Scroll Compressor
CAUTION: Oil is under pressure. See
instructions for adding oil.
1
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