Vertiv Liebert CRV - Page 45

To calculate the charge for the system:
1. Check the nameplate on the indoor unit for refrigerant type to be used. Unit control
configurations differ depending on refrigerant type.
2. The unit must be operating. Refer to the following if necessary:
• Checks to Perform after Start-up on page112 to operate the system.
• The operating manual for the Liebert MC Condenser.
Manuals are available at https://www.vertivco.com/en-us/support/.
3. Calculate the amount of charge for the system. See Refrigerant Charge Requirements for
Air-cooled Systems on page40.
4. Accurately weigh in as much of the system charge as possible before starting the unit. Do not
exceed the calculated charge by more than 0.5 lb (.23kg).
5. Turn on the Liebert MC disconnect switch.
6. Turn on the Liebert CRV disconnect switch, and operate the unit for 30minutes using the
charging function for each circuit of the system.
• You must operate the indoor fan using the "Diagnostic" menu of the Liebert iCOM control.
• A minimum 20psig (138kPa) must be established and maintained for the compressor to
operate.
• The charging function operates the compressor at full capacity and energizes the liquid-
line solenoid valve. The reheat and humidifier are disabled.
• The charging function can be reset as many times as required to complete unit charging.
7. Attach pressure and temperature instruments to the liquid-line of the indoor unit, measure the
initial subcooling, and continue to add charge until the recommended subcooling for the
current outdoor ambient temperature is reached. See Table 6.11 on the next page. Read the
outdoor ambient temperature from the Liebert MC condenser control menu ID F02.
NOTE: To determine subcooling measurement, you must measure the liquid-line pressure reading (at
the factory-installed Schrader tap) and obtain a temperature reading on the liquid line. Convert the
liquid-line pressure reading into a liquid temperature using a Pressure-Temperature Guide or Table 6.12
on page47. Subtract the measured temperature from the saturated-liquid temperature. The difference
is subcooling. Make sure to use the saturated liquid temperature to calculate subcooling.
8. As head pressure builds, the variable-fan-speed controlled condenser fan begins rotating. The
fan will run at full speed when sufficient head pressure is developed.
Vertiv | Liebert CRV Installer/User Guide | 45