Refrigerant Connections for Air-Cooled Units
Liebert
®
CRV
™
46
Sample Calculations
The Liebert MC is 40 ft. (12.2m) above the evaporator of an R-410A system. The outdoor ambient
from the Liebert MC condenser control menu ID F02, is 94.8°F (34.9°C). The liquid pressure is
421 psig (2903kPA) and the liquid temperature is 113°F (45.1°C). The subcooling from the
Liebert MC control is 7°F (3.9°C). Determine the subcooling and verify the calculated subcooling
against the reading of the Liebert MC control (menu ID F50 and F51).
Evaporator Subcooling Calculation
Subtract Line
(Measured Line Temperature) from Line
Temperature) to obtain Calculated Subcooling.
Elevation Correction
Subtract Line
(Condenser Elevation Temperature Correction) from Line
(Calculated
Subcooling) to obtain Corrected Subcooling.
Verification Against MC Condenser
Subtract Line
(MC Condenser Subcooling Reading) from Line
(Corrected Subcooling) to obtain
Difference.
• If Line
(Difference value) is less than ± 3°F (±1.7°C), NO charge adjustment is needed.
• If Line
(Difference value) is less than -3°F (-1.7°C), add additional charge.
If Line
(Difference value) is greater than +3°F (+1.7°C), the system is overcharged and
some of the charge must be removed.
9. 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.
Refrigerant Type
R-410A
1.
Ambient Temperature
94.8°F (34.9°C)
2.
Condenser Elevation
40ft. (12.2m)
3.
Condenser Elevation Temperature Correction
2°F (1.1°C)
4.
Liquid Line Pressure
421psig (2902kPa)
5.
Liquid Pressure Converted to Saturated Liquid
Temperature
120.3°F (49.0°C)
6.
Measured Liquid Line Temperature
113.2°F (45.1°C)
7.
MC Condenser Subcooling Reading (Menu ID
F50 for Circuit #1 or Menu ID F51 for Circuit #2)
7°F (3.9°C)
Line 5
120.3°F
(49.0°C)
Line 6
-113.2°F
(45.1°C)
8.
Calculated Subcooling
7.1°F or 7°F
(3.9°C or (4°C)
Line 8
7°F
(3.9°C)
Line 3
-2°F
- (2.2°C)
9.
Corrected Subcooling
5°F
(1.7°C)
Line 9
5°F
(1.7°C)
Line 7
-7°F
-(2.8°C)
10. Difference
-2°F
(-1.1°C)
Table 24
Difference in subcooling measurements—Indoor minus outdoor
Liebert MC elevation above
evaporator, ft (m)
Elevation Subcooling Correction - °F(°C)
80 (24)
60 (18)
40 (12)
20 (6)
Refrigerant
R-22
12 (6.6)
9 (5.0)
5 (2.8)
1 (0.6)
R-407C
10 (5.5)
7 (3.8)
4 (2.2)
1 (0.6)
R-410A
6 (3.3)
4 (2.2)
2 (1.1)
0 (0.0)
* Assumes liquid line is sized for no more than 2°F (1.1°C)pressure drop.