78
TK 61555-2-MM-EN
Refrigeration Maintenance
N
No
otte
e:: 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.
N
No
otte
e:: 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
N
No
otte
e:: Use the Service Test mode to operate units with an SR-3 controller.
For additional information regarding unit configuration categories, see SLXi charging
procedure later in this chapter.
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 each evaporator.
2. Install a gauge manifold.
3. Use the microprocessor thermometer to monitor the return air temperatures.
4. Run all the evaporators 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. R404A: The discharge pressure gauge should read 19.00 bar, 275 psi.
b. R452A: The discharge pressure gauge should read 20.00 bar, 290 psi.
N
No
otte
e:: If the discharge pressure is low, raise it by covering a portion of the condenser grille
with a piece of cardboard. For SLXi, it is located on the side of the unit, above the
control panel.
•
Suction pressure reading:
a. R-404A Systems: The compound gauge should be indicating 0.90 to 1.24 bar, 13 to
18 psi.
b. R-452A Systems: The compound gauge should be indicating 1.1 to 1.4 bar, 15 to 20
psi.
N
No
otte
e:: 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.
