Purpose: To check a unit for the recommended charge.
1. Install a calibrated gauge manifold.
2. Operate the unit in high speed cool.
3. Maintain a 0 F (-18 C) box temperature.
4. Cover the condenser as required to maintain discharge pressure equivalent for 100 F (38 C) ambient. Refer to the table under “Normal System Pressures Refrigeration Cycle” on page 6 to confirm refrigerant type and recommended pressures.
5. Suction pressure should be near the approximate pressure shown on the chart for a 0 F (-18 C) box.
6. Liquid refrigerant should be visible in the receiver tank sight glass when the unit is sufficiently charged.
7. If refrigerant needs to be added, refer to “Adding Refrigerant to a Partially Charged, Operating Unit” on page 17.
NOTE: If the ball drops and cooling is reduced before a 0 F (-18 C) box temperature can be reached, the unit probably has a low charge. A low charge is probably caused by a refrigerant leak that must be repaired.
IMPORTANT: Operating a unit with less than a full charge or with an overcharge can cause major compressor damage.
Always leak check, repair and properly check the refrigerant charge before returning a unit to service.
