Do not use the sight glass as an indicator when charging Liebert MC condenser systems.
5. Turn On the Liebert MC disconnect switch.
6. Turn on the indoor unit disconnect switch. Operate the unit for 30 minutes using the charging
function of the indoor-unit control for each circuit of the system. The charging function is in
the diagnostic section of Liebert iCOM® (see Liebert iCOM user manual, SL-18847, available at
www.VertivCo.com.
The charging function operates the compressor(s) at full capacity and energizes the liquid line
solenoid valve(s). The reheat and humidifier are disabled. Manual operation of the indoor fans
from the diagnostic menu of Liebert iCOM is required. A minimum 20psig (138kPa) must be
established and maintained for the compressor to operate. The charging function can be reset
as many times as required to complete unit charging.
Line Size O.D., in.
R-407C (R-22), lb/100 ft. (kg/30m) R-410A, lb/100 ft. (kg/30m)
Hot Gas Line Liquid Line Hot Gas Line Liquid Line
3/8 — 3.6 (1.6) — 3.2 (1.4)
1/2 0.5 (0.2) 6.7 (3.0) 0.7 (0.3) 5.9 (2.7)
5/8 0.8 (0.4) 10.8 (4.8) 1.1 (0.5) 9.6 (4.3)
3/4 1.2 (0.5) 16.1 (7.2) 1.6 (0.7) 14.3 (6.4)
7/8 1.7 (0.8) 22.3 (10.0) 2.3 (1.0) 19.8 (8.8)
1-1/8 2.9 (1.3) 38.0 (17.0) 3.9 (1.7) 33.8 (15.1)
1-3/8 4.4 (2.0) 57.9 (25.9) 5.9 (2.6) 51.5 (23.0)
1-5/8 6.2 (2.8) — 8.4 (3.7) —
Data based on 50°F Evap, 15°F superheat, 125°F SCT, 10°F subcooling.
Source: DPN002411, Rev. 7
Table 5.9 Charge amounts per 100 ft. (30m) of pipe by line size
7. Attach pressure and temperature instruments to the liquid line of the indoor unit. Measure the
initial subcooling and continue to add charge until reaching the recommended subcooling for
the current outdoor ambient temperature (see Table 5.10 below). The outdoor ambient can be
read from the Liebert MC condenser control menu ID F02.
NOTE: To determine subcooling measurement, a liquid line pressure reading (at the factory-installed
Schrader tap) needs to be measured along with obtaining a temperature reading on the liquid line.
Convert the liquid line pressure reading into a temperature by utilizing a Pressure-Temperature Guide
or Table 5.11 on the facing page. The difference between this converted temperature and the actual
temperature will determine the system’s subcooling. For R-407C make sure to use the saturated liquid
temperature to calculate subcooling.
Ambient Temp °F (C°) Subcooling °F (C°)
0 (-17.8) 22 (12.0)
10 (-12.2) 22 (12.0)
20 (-6.7) 22 (12.0)
30 (-1.1) 22 (12.0)
Table 5.10 Target subcooling for ambient outdoor temperature
Vertiv | Liebert® MC™ Installer/User Guide | 80
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