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TK 61753-2-MM-EN
Refrigeration Maintenance
NNoottee:: Some of the following service procedures are regulated by EU regulation known as "F-Gas" and /or local laws. All
regulated refrigeration service procedures must be performed by a certified technician, using approved
equipment and complying with all EU and local laws.
A Service Test mode on these controllers allows technicians to operate the unit under known conditions while
performing diagnosis and service procedures. See the appropriate Operating and Diagnostic manual for
instructions on how to use the Service Test mode.
NNoottee:: The following procedures can be found in the Thermo King Truck and Trailer Diagnosing Manual TK 60201-8-OD
1. Installing Gauge Mainfold
2. Compressor Pump Down and Checkout
3. Low Side Pump Down
Refrigerant Charge
NNoottee:: Use the Service Test mode to operate units.
Testing The Refrigerant Charge With An Empty Trailer
If the unit has an insufficient charge of refrigerant, the evaporator will be “starved” and the box temperatures will rise
even though the unit is operating. The suction pressure will drop as the refrigerant charge decreases. If the unit has an
overcharge of refrigerant, the unit may not cool properly and the suction and discharge pressure may be high. The
charge may be determined by inspection of the refrigerant through the receiver tank sight glasses with the following
conditions established:
1. Place a test box over evaporator.
2. Install a gauge manifold.
3. Use the microprocessor thermometer to monitor the return air temperatures.
4. Run the evaporator in cool until the air in each box is at -18 C (0 F). By allowing a box to leak a small amount, you
will be able to maintain -18 C (0 F).
5. The ball in the sight glass should be floating under the conditions below. If refrigerant is not visible in the receiver
tank sight glass, the unit is low on refrigerant.
• Discharge pressure reading:
a. R452A: The discharge pressure gauge should read 20.00 bar, 290 psi.
NNoottee:: If the discharge pressure is low, raise it by covering a portion of the condenser grille with a piece of
cardboard.
•
• Suction pressure reading:
a. R-452A Systems: The compound gauge should be indicating 1.1 to 1.4 bar, 15 to 20 psi.
NNoottee:: If there is any doubt about the accuracy of the discharge or compound gauge, check the calibration.
Testing the Refrigerant Charge with a Loaded Trailer
1. Install a gauge manifold.
2. Run the unit on the Cool cycle 5 to 10 minutes.
3. Cover at least three quarters of the condenser grille to drive any excess refrigerant from the condenser coil into the
receiver tank.
4. As the head pressure is rising, check the receiver tank sight glass.
5. The ball in the sight glass should be floating. If there is no indication of refrigerant in the sight glass, the unit is low
on refrigerant.
6. Under these conditions, refrigerant should be visible in the receiver tank sight glass. If refrigerant is not visible in the
receiver tank sight glass, the unit is low on refrigerant.
NNoottee:: If the ball floats, there is sufficient refrigerant in the unit for that load at that particular compartment
temperature. This test does not determine if the unit contains a full charge of refrigerant.
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