Thermo King T-500R Maintenance Manual page 193

Unit Charging (UT-Series)
Initial System Charge
The UT-Series utilizes a receiver tank sight glass. This is used in order to attain an optimum charge given varied installations
(suction/ liquid line lengths vary).
Before charging the system, make sure that the refrigerant lines from the gauge manifold to the refrigerant supply bottle have
been evacuated or purged.
1. Backseat the suction service valve and make sure the receiver tank outlet valve is still open. Refrigerant will be added to the
high side of the unit with the unit OFF.
Set the refrigerant supply bottle for liquid. Open the gauge manifold hand valve and add partial charge of 2.5 kg (5.5 lb.) of
R-404A/R-452A refrigerant.
2. Do not add more than this. Remainder of charge will be added through suction service valve while unit is running.
3. After the liquid refrigerant is added, close the gauge manifold hand valve.
4. Remove hose from discharge line. A low loss fitting on this hose will prevent excessive loss of refrigerant.
5. Back seat (close) the receiver tank outlet valve.
6. Front seat the suction service valve (SSV). Run the unit until a 21 to 35 kPa (3 to 5 psi) reading is obtained on the suction
gauge. Stop the unit. Do not run the unit into a deep vacuum as it may damage the scroll compressor.
7. Back seat (close) suction service valve.
8. Remove the evacuation station hoses.
9. Cap service valve ports, backseat (close) suction service valve (SSV).
Final System Charge
1. Install a calibrated gauge manifold set on the suction service valve and the discharge port of the scroll compressor.
2. Start the unit and use the Service Test mode to run the unit in COOL. Maintain a -17.8 C (0 F) box and 37 C (99 F) ambient.
Suction pressure should be 83-174 kPa (12-20 psig) and discharge pressure to 2000-2137 kPa (290-310 psig) (suction service
valve cracked). Cover the condenser coil if needed.
3. Observe the suction pressure and slowly open gauge manifold hand valve to allow liquid refrigerant to flow into suction
service valve. Control liquid flow so suction pressure increases approximately 138 kPa (20 psig).
4. Add refrigerant until sight glass is 3/4 full - i.e. sight glass level ball should be at this marker.
5. Stop the flow of refrigerant into the system by closing the low-side gauge manifold hand valve.
6. Continue to operate unit in COOL for 10 minutes to ensure ball is at correct level in receiver tank sight glass. The total charge
in the system will be about 4.0-4.5 kg (8.8-9.9 lb) of refrigerant.
Refrigeration Maintenance 10-9