Nor-Lake Refrigeration Systems - Manual (Page 17)

09/14 Rev. E 101628 17
Example: R-404A system with 1170 equivalent feet of 1/2 inch tubing in the condenser.
(1170 x 0.93)/100 = 10.9 pounds
TABLE 4
Equivalent Length Refrigerant per 100 Feet
Tubing
Size
for Each of Tubing
Return Bend Pounds @-20°F
Inches Feet R-404A
3/8 .20 .050
1/2 .25 .093
5/8 .30 .149
The amount of refrigerant calculated using Table 4 must be corrected since the condenser
might be already partially flooded, especially if charging is being done at low ambient
temperatures. Table 5 provides information on the percentage of the condenser to be flooded at
various ambient temperatures for high, medium, and low suction condensing units. To
determine the extra charge, determine the difference in percentage between the charging
ambient temperature and the minimum winter ambient temperature and multiply the figure by
the pounds of refrigerant calculated above.
Example: High Suction Condensing Unit, 40° Evaporating Temperature
-20°F Minimum Winter Ambient 79
50°F Charging Ambient -40
39
10.9 pounds x.39 = 4.3 pounds of extra charge
TABLE 5
Condenser Low Suction Medium Suction High Suction
Ambient Condensing Units Condensing Units Condensing Units
Temperature Evaporating Temperature - °F
°F -35° -25° -15° -5° 0° 10° 20° 30° 35° 40° 45° 50°
80° 27 15 0 0 0 0 0 0 0 0 0 0
70° 62 49 35 15 40 24 0 0 0 0 0 0
60° 76 65 56 45 60 47 33 17 26 20 10 4
50° 83 75 68 60 70 60 50 38 45 40 33 28
40° 86 80 74 68 76 68 60 50 56 52 46 42
30° 88 84 79 74 80 73 66 59 64 60 55 51
20° 90 86 82 78 83 77 72 65 69 66 62 59
0° 92 89 86 82 87 83 78 73 76 73 70 68
-20° 94 91 88 86 91 87 82 77 80 79 76 73
-40° 97 94 92 90 94 89 84 79 83 81 79 77
4. After the system has stabilized, check for excessive liquid flood back to the compressor. If
flooding occurs, adjust the expansion valve as required to correct the situation.
5. Do not leave the system unattended until it reaches normal operating conditions, and do not
allow product to be stored in the cold room until a complete system operational check is
completed.