Thermo King 914 724, Руководство пользователя

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Refrigeration Maintenance (Rev. 1/99)
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15. Close the low side valve on the gauge manifold and
operate the unit for 15 minutes.
16. Model 20 only.
a. Turn the unit OFF and shut off the truck engine.
b. Connect the electric power receptacle to an appro-
priate electric power supply. Start and run the unit
in cool on electric operation for a minimum of 15
minutes.
c. Turn the unit OFF and disconnect the electric
power supply. Start the truck and run the unit in
cool on engine operation for a minimum of 15
minutes.
17. Check the receiver tank sight glass with the unit run-
ning in cool, the box temperature at 0 F (-20 C), and a
head pressure of at least 180 psig (1241 kPa) for
R-134a systems and 275 psig (1896 kPa) for R-404A
systems. The ball should be at the top of the sight glass.
If not, open the valve on the refrigerant drum to deliv-
ery liquid and open the low side valve on the gauge
manifold. Add refrigerant liquid until the ball in the
receiver tank sight glass reaches the top of the sight
glass, then close the valve on the refrigerant drum and
close the low side valve on the gauge manifold.
18. Stop the unit, shut OFF the truck engine and remove the
gauge manifold set.
19. The above conditions MUST be established each time
the refrigerant level is checked or if refrigerant needs to
be added for any reason.
NOTE: To prevent oil migration from one compressor to
another, and for proper oil return when a compressor is
operating, operate the compressor for a minimum of 15
minutes. Do not operate the compressor for shorter inter-
vals.
Checking the Refrigerant Charge
If the unit has an insufficient charge of refrigerant, the evap-
orator will be “starved” and the box temperature will rise
even though the unit is operating. Also, an insufficient
charge does not circulate enough oil to properly lubricate
the compressor. The charge may be determined by inspec-
tion of the refrigerant through the receiver tank sight glass
with the following conditions established:
Testing the Refrigerant Charge with an Empty Box
1. Place a test box over the evaporator.
2. Install a gauge manifold set.
3. Run the unit in cool on engine-driven compressor oper-
ation until the thermometer reads 0 F (-18 C). By
allowing the box to leak a small amount, you will be
able to maintain 0 F (-18 C).
4. The discharge or head pressure gauge should read
175 psi (1206 kPa) on the gauge manifold. If the pres-
sure is below this, it can be raised by covering a portion
of the condenser grille with a piece of cardboard.
5. Under these conditions the ball should be at the top of
the sight glass to indicate a full charge.
Testing the Refrigerant Charge with a Loaded Box
1. Install a gauge manifold.
2. Run the unit in cool cycle on engine-driven compressor
operation.
3. Cover the condenser to drive any excess refrigerant
from the condenser into the receiver tank.
4. As the head pressure rises, check the receiver tank sight
glass. If there is no indication of refrigerant in the
receiver tank sight glass, indicated by the float ball
being down in the bottom sight glass, the unit contains
less than a full charge and more refrigerant MUST be
added. Refer to Charging the Refrigeration System to
add refrigerant.