Thermo King SLXi Spectrum, Maintenance Manual

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Refrigeration Maintenance 10-5
REFRIGERANT CHARGE
NOTE: Use the Service Test mode to operate units with a TG-VI, µP-IV, µP-V, µP-VI, SR-2 or SR-3 controller. See the
appropriate Controller Operation and Diagnosis manual for instructions.
NOTE: For additional information regarding category A, B & C for SLX/SLXe/SLXi, see SLX/ SLXe/SLXi charging
procedure later in this chapter. For SLXe Spectrum, use Category C.
Checking Refrigerant Charge with an Empty Trailer
If the unit has an insufficient charge of refrigerant, the evaporator will be “starved” and the compartment temperature will rise
even though the unit is operating. The suction pressure will decrease as the refrigerant charge decreases. The charge may be
determined by inspection of the refrigerant through the receiver tank sight glass with the following conditions established:
1. Place a test compartment over the evaporator.
2. Place a thermometer (P/N 204-135) test lead in the compartment near the evaporator return air opening.
3. Install the gauge manifold.
Note: For Category B unit, close all doors on unit and ensure all unit panels and skins are securely attached.
4. Operate the unit (and all remote evaporators) on Cool until the air in the compartment indicates -18 C. By allowing the
compartment to leak a small amount, you can maintain -18 C.
5. The ball in the sight glass should be floating under the conditions below.
For category B SLX, open doors to view the sight glass and close again
• Discharge pressure reading:
R404A:
The discharge pressure gauge should read 19.00 bar, 275 psi.
R452A:
The discharge pressure gauge should read 20.00 bar, 290 psi.
NOTE: If the discharge pressure is low, raise it by covering a portion of the condenser grille with a piece of cardboard. On
SL and SLe models, the condenser grille is located above the unit control panel. For SLX, SLXe and SLXi, it is located on the
side of the unit, above the control panel.
• Suction pressure reading:
R-404A Systems:
The compound gauge should be indicating 0.90 to 1.24 bar, 13 to 18 psi.
R-452A Systems:
The compound gauge should be indicating 1.1 to 1.4 bar, 15 to 20 psi.
NOTE: If there is any doubt about the accuracy of the discharge or compound gauge, check the calibration.
Checking Refrigerant Charge with a Loaded Trailer
1. Install a gauge manifold (optional).
2. Operate the unit (and all remote evaporators) 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. On SL and SLe models, the condenser grille is located above the unit control panel. For SLX, SLXe and SLXi, it is
located on the side of the unit, above the control panel.
Note: For Category B unit, close all doors on unit and ensure all unit panels and skins are securely attached.
4. As the head pressure is rising, check the receiver tank sight glass.