Thermo King 919180, Руководство пользователя

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Refrigeration Maintenance
90
5. If the unit is not fully charged, attach the
gauge manifold set to the suction service valve
and the discharge service port (see Figure 53
on page 93).
6. Open the refrigerant supply valve for liquid.
7. Start the unit and use the Service Test mode to
run the unit in high speed cool. See the
µ
P-T
Microprocessor Diagnosis Manual for
information about the Service Test mode.
8. Observe the suction pressure and slowly open
the gauge manifold hand valve to allow liquid
refrigerant to flow into the suction service
valve. Control the liquid flow so the suction
pressure increases approximately 20 psig
(138 kPa). Maintain a discharge pressure of at
least 275 psig (1896 kPa).
9. Add refrigerant until the ball in the receiver
tank sight glass rises to the middle of the sight
glass, then close the gauge manifold hand
valve. Make sure the liquid level does not rise
above the top of the sight glass.
10. Continue to operate the unit in high speed cool
for another 10 minutes and check the
refrigerant level in the receiver tank sight
glass. If the level has dropped, add liquid
refrigerant until the level stabilizes near the
middle of the sight glass. Do not exceed the
recommended refrigerant charge for the unit
model.
Remove Refrigerant Hoses
1. A low leak fitting must be used on hoses when
Schrader port fittings are encountered on units
(unit Off).
2. With a low leak fitting on the discharge gauge
line, remove this line from the unit.
3. Back seat the receiver tank service valve (run
the unit until a 3 to 5 psig [21 to 35 kPa]
reading is obtained on the suction gauge).
Stop the unit.
4. Back seat the suction service valve and
remove all remaining hoses.
5. Install and tighten service port and valve stem
caps.
6. Unit is ready for a functional check out.
Refrigerant Leaks
Use a reliable leak detector (e.g., electronic
detector) to leak test the refrigeration system.
Inspect for signs of oil leakage which is the first
sign of a leak in the refrigeration system.
NOTE: It is normal for compressor shaft seals to
have a slightly oily film.
Refrigerant Charge
Testing the Refrigerant Charge with
an Empty Box
If the unit has an insufficient charge of refrigerant,
the evaporator will be “starved” and the box
temperature will rise even though the unit is
operating. The suction pressure will drop as the
refrigerant charge decreases. The charge may be
determined by inspection of the refrigeration
through the receiver tank sight glass with the
following conditions established:
1. Place a test box over the evaporator.
2. Place a thermometer (see Tool Catalog) test
lead in the box near the evaporator return air
opening.
3. Install the gauge manifold.
4. Run the unit on high speed cool until the air in
the box indicates 0 F (-18 C). By allowing the
box to leak a small amount, you will be able to
maintain 0 F (-18 C).
5. The discharge or head pressure gauge should
read 275 psig (1896 kPa).
If the pressure is below this, it can be raised by
covering a portion of the condenser coil with a
piece of cardboard.
6. The compound gauge should be indicating 13
to 18 psig (90 to 124 kPa) gauge pressure.
If there is any doubt about the unit gauge,
check the calibration.
7. Under these conditions, the ball in the receiver
tank sight glass should be floating. If there is
no indication of refrigerant in the receiver tank
sight glass, the unit is low on refrigerant.