Table 6 Target Subcooling For Ambient Outdoor Temperature - Emerson Liebert Challenger iCOM 3000 Operation & Maintenance Manual

Table 6 Target subcooling for ambient outdoor temperature
Ambient Temp
°F (C°)
0 (-17.8)
10 (-12.2)
20 (-6.7)
30 (-1.1)
40 (4.4)
50 (10.0)
60 (15.6)
70 (21.1)
9. Verify the subcooling calculated from measured values at the evaporator against the subcooling
reading of the Liebert MC
differs from the Liebert MC subcooling by more than 3°F (1.7°C), then adjust the charge amount
to achieve the target subcooling per Table 6 based the Liebert MC control subcooling.
Failure to check measured subcooling with refrigerant gauges against the Liebert MC subcooling
may result in an overcharged system. See NOTE below and Table 7 for correction to Liebert MC
subcooling that may be required based on condenser elevation above the indoor evaporator.
NOTE
If the condenser is part of an R-22 system, the configuration of the condenser must be changed
to read the subcooling correctly. The value of menu ID C09 of the Liebert MC control must be
changed to "1".
NOTE
The evaporator subcooling will be greater than the condenser subcooling when the Liebert MC
is mounted higher than the indoor evaporator. Subcooling adjustment is needed when the
Liebert MC is located greater than 40 ft above evaporator.
Sample Calculations
The Liebert MC is 40 ft. above the evaporator of an R-407C system. The outdoor ambient from the
Liebert MC condenser control menu ID F02, is 94.8°F. The liquid pressure is 300 psig and the liquid
temperature is 113°F. The subcooling from the Liebert MC control is 5°F. Determine the subcooling
and verify the calculated subcooling against the reading of the Liebert MC control [menu ID F50 &
F51].
Evaporator Subcooling Calculation
Refrigerant Type: R-407C
a. Ambient Temperature: 94.8°F
b. Condenser Elevation: 40 ft.
c. Condenser Elevation Temperature Correction: 4°F
d. Liquid Line Pressure: 300
e. Liquid Pressure converted to Saturated Liquid Temperature: 120.3°F
f. Measured Liquid Line Temperature: 113.2°F
g. MC Condenser Subcooling Reading: 5°F
(Menu ID F50 for Circuit #1 or Menu ID F51 for Circuit #2)
Subtract Line f (Measured Line Temperature) from Line e. (Liquid Pressure converted to
Temperature) to obtain Calculated Subcooling.
Line e:
Line f:
h. Calculated Subcooling:
™
Liebert ® Challenger 3000
Subcooling Ambient Temp
°F (C°)
22 (12.0) 80 (26.7)
22 (12.0) 90 (32.2)
22 (12.0) 95 (35.0)
22 (12.0) 100 (37.8)
22 (12.0) 105 (40.6)
21 (11.7) 110 (43.3)
19 (10.8) 125 (51.7)
17 (9.3)
control [menu ID F50 & F51]. If the subcooling calculated with gauges
™
120.3°F
-113.2°F
7.1°F or 7°F
Subcooling
°F (C°) °F (C°)
13 (7.2)
9 (5.0)
7 (3.9)
5 (2.9)
3 (1.8)
1 (0.7)
16
Component Operation and Maintenance
0 0