Carrier 38HDR Installation Instructions Manual page 13

Subcooling Method
NOTE: Units are charged at the factory for 15 ft of tubing. Adjust
charge by plus or minus 0.6 oz per foot of tubing greater or less
than 15 ft respectively.
For 38HDR units, the subcooling method is used to check and
adjust charge during the cooling season. Refer to Table 4 and the
following procedure:
1. Operate unit a minimum of 15 minutes before checking
charge.
2. Measure liquid line temperature near liquid line service
valve, and measure the liquid pressure at the liquid line ser-
vice valve. Use a digital thermometer for all temperature
measurements. DO NOT use mercury or dial- -type ther-
mometers.
LIQUID
PRES-
SURE AT
SERVICE
8
VALVE
psig
°C
_F
189 58 32
195 60 33
202 62 34
208 64 36
215 66 37
222 68 38
229 70 39
236 72 40
243 74 41
251 76 42
259 78 43
266 80 44
274 82 46
283 84 47
291 86 48
299 88 49
308 90 50
317 92 51
326 94 52
335 96 53
345 98 54
354 100 56
364 102 57
374 104 58
384 106 59
395 108 60
406 110 61
416 112 62
427 114 63
439 116 64
450 118 66
462 120 67
474 122 68
486 124 69
499 126 70
511 128 71
Table 4—Subcooling Charging Table
REQUIRED LIQUID LINE TEMPERATURE
Required Subcooling Temperature
10 12
°C
_F _F
56 31 54
58 32 56
60 33 58
62 34 60
64 36 62
66 37 64
68 38 66
70 39 68
72 40 70
74 41 72
76 42 74
78 43 76
80 44 78
82 46 80
84 47 82
86 48 84
88 49 86
90 50 88
92 51 90
94 52 92
96 53 94
98 54 96
100 56 98
102 57 100
104 58 102
106 59 104
108 60 106
110 61 108
112 62 110
114 63 112
116 64 114
118 66 116
120 67 118
122 68 120
124 69 122
126 70 124
3. Refer to Table 4. Find the temperature point at which the
required subcooling temperature intersects the measured liq-
uid line pressure.
4. If the measured liquid line temperature does not agree with
the required liquid line temperature, ADD refrigerant to
lower the temperature, or REMOVE refrigerant to raise the
temperature (allow a tolerance of ±3_F/1.67_C).
14
°C °C
_F
30 52 29
31 54 30
32 56 31
33 58 32
34 60 33
36 62 34
37 64 36
38 66 37
39 68 38
40 70 39
41 72 40
42 74 41
43 76 42
44 78 43
46 80 44
47 82 46
48 84 47
49 86 48
50 88 49
51 90 50
52 92 51
53 94 52
54 96 53
56 98 54
57 100 56
58 102 57
59 104 58
60 106 59
61 108 60
62 110 61
63 112 62
64 114 63
66 116 64
67 118 66
68 120 67
69 122 68
13
16 18
°C
_F _F
50 28 48
52 29 50
54 30 52
56 31 54
58 32 56
60 33 58
62 34 60
64 36 62
66 37 64
68 38 66
70 39 68
72 40 70
74 41 72
76 42 74
78 43 76
80 44 78
82 46 80
84 47 82
86 48 84
88 49 86
90 50 88
92 51 90
94 52 92
96 53 94
98 54 96
100 56 98
102 57 100
104 58 102
106 59 104
108 60 106
110 61 108
112 62 110
114 63 112
116 64 114
118 66 116
120 67 118
°C
27
28
29
30
31
32
33
34
36
37
38
39
40
41
42
43
44
46
47
48
49
50
51
52
53
54
56
57
58
59
60
61
62
63
64
66