Adjusting Sub-cooling and Superheat
Temperatures
1. The system is overcharged if the sub-cooling tem-
perature is too high and the evaporator is fully loaded
(low loads on the evaporator result in increased sub-
cooling) and the evaporator superheat is within the
temperature range as shown in the table above (high
superheat results in increased sub-cooling).
2. Correct an overcharged system by reducing the
amount of refrigerant in the system to lower the
sub-cooling.
3. The system is undercharged if the evaporator super-
heat is too high, compressor discharge gas tempera-
ture is too high and the sub-cooling is too low.
4. Correct an undercharged system by adding refrig-
erant to the system to reduce superheat and raise
sub-cooling.
5. If the sub-cooling is correct and the superheat is too
high, the TXV may need adjustment to correct the
superheat.
CAUTION
Do not overcharge!
Refrigerant overcharging leads to excess refrigerant in
the condenser coils resulting in elevated compressor dis-
charge pressure.
Table R2: R410a Refrigerant Temperature vs. Pressure
°F PSIG °F PSIG °F PSIG °F PSIG °F PSIG
20
78.3 47 134.7 74 213.7 101 321.0 128 463.2
21
80.0 48 137.2 75 217.1 102 325.6 129 469.3
22
81.8 49 139.7 76 220.6 103 330.2 130 475.4
23
83.6 50 142.2 77 224.1 104 334.9 131 481.6
24
85.4 51 144.8 75 227.7 105 339.6 132 487.8
25
87.2 52 147.4 79 231.3 106 344.4 133 494.1
26
89.1 53 150.1 80 234.9 107 349.3 134 500.5
27
91.0 54 152.8 81 238.6 108 354.2 135 506.9
28
92.9 55 155.5 82 242.3 109 359.1 136 513.4
29
94.9 56 158.2 83 246.0 110 364.1 137 520.0
30
96.8 57 161.0 84 249.8 111 369.1 138 526.6
31
98.8 58 163.8 85 253.7 112 374.2 139 533.3
32 100.9 59 166.7 86 257.5 113 379.4 140 540.1
33 102.9 60 169.6 87 261.4 114 384.6 141 547.0
34 105.0 61 172.5 88 265.4 115 389.9 142 553.9
35 107.1 62 175.4 89 269.4 116 395.2 143 560.9
36 109.2 63 178.4 90 273.5 117 400.5 144 567.9
37 111.4 64 181.5 91 277.6 118 405.9 145 575.1
38 113.6 65 184.5 92 281.7 119 411.4 146 582.3
39 115.8 66 187.6 93 285.9 120 416.9 147 589.6
40 118.1 67 190.7 94 290.1 121 422.5 148 596.9
41 120.3 68 193.9 95 294.4 122 428.2 149 604.4
42 122.7 69 197.1 96 298.7 123 433.9 150 611.9
43 125.0 70 200.4 97 303.0 124 439.6
44 127.4 71 203.6 98 307.5 125 445.4
45 129.8 72 207.0 99 311.9 126 451.3
46 132.2 73 210.3 100 316.4 127 457.3
VCES-VHC-IOM-1F – VHC-36, -42 & -50
90
