Liebert PX018 Installer's/User's Manual page 48

Optimizing Refrigerant Charge on Water/Glycol Units
Liebert PDX/PCW 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 5.11 below, describes the factory charge for the unit.
Table 5.11 Approximate R-410A refrigerant factory charge
for water/glycol-cooled Liebert PDX
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—R-410A
the liquid-saturation temperature. The difference is subcooling.
3. Adjust refrigerant charge levels as needed to achieve subcooling range of 12 to 14°F
(6.7 to 7.8°C) while maintaining full load conditions.
Vertiv | Liebert® PDX™ and PCW™ Installer/User Guide |
Downflow,
Model
lb (kg)
PX011 5.7 (2.6)
PX018 6.2 (2.8)
PX023 6.2 (2.8)
PX029 8.5 (3.9)
on page 42. Subtract the measured temperature from
Upflow,
lb (kg)
6.3 (2.9)
9.0 (4.1)
9.0 (4.1)
9.5 (4.3)
48