4. After completion of leak testing, release the test pressure, (observe local code) and pull an
initial deep vacuum of 500 microns on the system with a suitable pump.
5. After 4hours, check the pressure readings and, if they have not changed, break vacuum with
dry nitrogen. Pull a second and third vacuum to 500 microns or less. Re-check the pressure
after 2hours.
When the 3 checks are complete, proceed to Charging Air-cooled Systems with
UnheatedReceivers below.
Charging Air-cooled Systems with UnheatedReceivers
NOTICE
Risk of improper refrigerant charging. Can cause equipment damage.
R-410A is a blended refrigerant and must be introduced and charged from the cylinder only as
a liquid.
When adding liquid refrigerant to an operating system, it may be necessary to add the
refrigerant through the compressor suction service valve.service . Care must be exercised to
avoid damage to the compressor. We recommend connecting a sight glass between the
charging hose and the compressor suction service valve. This will permit adjustment of the
cylinder hand valve so that liquid can leave the cylinder while allowing vapor to enter the
compressor.
NOTICE
Risk of refrigerant overcharge. Can cause equipment damage.
Do not use the sight glass as an indicator when charging Liebert MC condenser systems.
To calculate the charge for the system:
1. Check the unit's nameplate for refrigerant type to be used. Unit control configurations differ
depending on refrigerant type.
2. The unit must be operating, refer to Checklist for Completed Installation on page57.
3. Calculate the amount of charge for the system. See Refrigerant Charge Requirements for
Air-cooled Systems on page36.
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 (.23kg).
5. Turn on the Liebert MC Condenser disconnect switch.
NOTE: We recommend charging the unit with the return-air setpoint between 75°F to 85°F (24 to
29°C). The return-air temperature to the charged unit must be stable and must be maintained greater
than 65°F (18°C). If this is not possible from lack of heat load, then use load banks to offset the cooling
load during start up. See Refrigerant-level Sight Glasses ontheUnheated Receiver on the facing page
for the proper charge level in the receiver based on return-air temperature and outdoor temperature at
time of charging.
6. Turn on the indoor-unit disconnect switch.
Vertiv | Liebert® PDX™ and PCW™ Installer/User Guide | 46
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