Vertiv Liebert CRV - Superheat and Refrigerant Charge Optimization

6.2.7 Superheat and Refrigerant Charge Optimization
Superheat on All Units
Compressor suction superheat for all unit types should be checked and adjusted per Table 6.14 on the
facing page. See Determining Suction Superheat on page136 and Adjusting Superheat Setting with the
TXV on page136 for superheat measurement and adjustment methods.
Optimizing Refrigerant Charge on Water/Glycol Units
Liebert CRV water/glycol systems are factory-charged with R-410A refrigerant and will operate without
refrigerant-charge adjustment at a wide range of return-air temperatures and water/glycol entering
temperatures. Adjusting the factory refrigerant charge while operating the unit at full-load room
conditions and at typical water/glycol temperatures can maximize the cooling capacity and unit
efficiency.
Table 6.13 below, describes the factory charge for the unit.
MODEL
R-410A REFRIGERANT CHARGE, LB
(KG)
INITIAL OIL CHARGE, OZ. (KG)*
CR019RW 6.5 (2.9) 60 (1.68)
CR020RW 13.0 (5.9) 60 (1.68)
CR035RW 17.0 (7.7) 110 (3.12)
1. The recommended oil is EMKARATE RL 32-3MA.
Table 6.13 R410-A refrigerant factory charge and oil charge forwater-cooledLiebertCRV
To optimize the refrigerant charge:
1. Operate the unit at full heat load, normal room conditions and normal water/glycol fluid
temperatures for a minimum of 30 minutes before measuring stable unit superheat and
subcooling temperatures and adjusting charge levels.
• Condensing temperatures should be in range of 100 to 130°F (38 to 54°C) depending on
fluid type and fluid temperature.
• Full heat load is required to stabilize the system and prevent digital scroll-compressors
from modulating.
2. Attach pressure and temperature instruments to the liquid line of the indoor unit. Use the
factory-installed Schrader valve located in the liquid line downstream of the condenser.
Measure the initial subcooling.
NOTE: To determine subcooling measurement, a liquid-line pressure reading (at the factory-installed
Schrader tap) must be measured along with the temperature reading on the liquid line. Convert the
liquid-line pressure reading into a liquid temperature by utilizing a Pressure-temperature Guide or
Liquid pressure andtemperature chart on page47. Subtract the measured temperature from the liquid-
saturation temperature. The difference is subcooling.
3. Adjust refrigerant charge levels as needed to achieve subcooling and superheat ranges shown
for your model in Table 6.14 on the facing page, while maintaining full load conditions.
Vertiv | Liebert CRV Installer/User Guide | 50