Thermo King – Adding Refrigerant to a Partially Charged, Operating Unit

Purpose: To add refrigerant to a unit low on charge.
1. Install a calibrated gauge manifold.
2. Attach the manifold service line to the refrigerant bottle and purge the line from the bottle to the manifold.
3. Set the refrigerant bottle to withdraw liquid refrigerant.
4. Operate the unit in high speed cool:
• Maintain discharge pressure for 100 F (38 C) ambient.
• R-404A = 325 psig
• R-134a = 190 psig
• Observe suction pressure. Refer to the table under “Normal System Pressures Refrigeration Cycle” on page 6.
5. Open the gauge manifold low pressure hand valve only enough to permit suction pressure to increase approximately 25 psig above noted suction pressure. This will meter liquid refrigerant slowly into the low side.

6. Maintain the discharge pressure and add liquid refrigerant until it appears in the receiver tank sight glass.
7. When liquid refrigerant appears in the receiver tank sight glass, the unit has enough refrigerant to operate at the present box temperature.
8. Close valve on refrigerant tank.
9. Remove gauges and reinstall valve caps.

CAUTION: Do not overcharge the unit. If an overcharge is suspected, perform the Overcharge Test.

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