CHARGING PROCEDURE
AIRFLOW CHECK - Both airflow and refrigerant charge must be monitored
for a proper system set‐up. It may be necessary to alternately check and
adjust the airflow and the refrigerant charge.
NOTE - Be sure that filters and indoor and outdoor coils are clean before testing.
To determine temperature drop across indoor coil (Delta-T), measure the entering air dry
bulb (DB) and wet bulb (WB) temperatures at the indoor coil. Find Delta-T in table 1. Measure
coil's leaving air DB and subtract that value from entering air DB. The measured difference
should be within +
3ºF (+1.8ºC) of table value; if too low, decrease the indoor fan speed (refer
to indoor unit for information). If the Delta-T is too high, increase the indoor fan speed. Repeat
charging procedure and Delta-T (air flow adjustment) procedure until both are correct.
Example: assume entering air DB - 72, WB - 64, leaving DB - 53. Therefore, Delta-T should
be 15 (per table); delta across coil is 72 - 53 or 19 (which is 4ºF higher than table value); action
necessary: increase fan speed.
Table 1. Evaporator Coil Delta-T
Dry bulb 80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
temperature 78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
of air 76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
entering 74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
indoor 72 20 20 19 18 17 17 16 15 15 14 13 12 11 10
coil (ºF) 70 19 19 18 18 17 17 16 15 15 14 13 12 11 10
ºF 57 58 59 60 61 62 63 64 65 66 67 68 69 70
[ Wet bulb temperature of air entering indoor coil ]
Table 2. Superheat (SH) Value RFC System - +5ºF
40 15 18 20 23 26 29 32 34 38 41 43 46 48 51
45 13 16 18 21 24 27 30 33 36 39 41 44 46 49
50 11 14 16 19 22 25 28 31 34 37 39 42 44 47
Dry bulb 55 9 12141720232730333638404244
temperature 66 7 10121518212427303335384043
of ambient 65 ‐ 6 10 13 16 19 21 24 27 30 33 36 38 41
air entering 70 ‐ ‐ 7 1013161921242730333639
outdoor 75 ‐ ‐ ‐ 6 9 121518212428313437
unit (ºF) 80 ‐ ‐ ‐ ‐ 5 8 12 15 18 21 25 28 31 35
85 ‐‐‐‐‐‐811151922263033
90 ‐‐‐‐‐‐59131620242731
95 ‐‐‐‐‐‐‐6101418222529
100 ‐‐‐‐‐‐‐‐81216212428
105 ‐‐‐‐‐‐‐‐5913172226
110 ‐‐‐‐‐‐‐‐‐611152025
115 ‐‐‐‐‐‐‐‐‐‐8141824
ºF 50 52 54 56 58 60 62 64 66 68 70 72 74 76
[ Wet bulb temperature of air entering indoor coil ]
Model -18 -24 -30 -36 -42 -48 -60
Table 3- Normal Operating Pressures
1
°F(°C)
2
TXV System - Liquid Line (+10 psig) / Vapor Line (+5 psig)
65 (18) 230 / 138 233 / 138 230 / 136 240 / 137 236 / 138 238 / 136 239 / 133
75 (24) 265 / 140 271 / 140 265 / 139 278 / 139 273 / 141 277 / 139 278 / 136
85 (29) 307 / 142 313 / 143 308 / 141 321 / 140 318 / 143 320 / 139 323 / 138
95 (35) 351 / 144 361 / 145 355 / 144 368 / 142 366 / 146 369 / 141 370 / 140
105 (41) 407 / 145 412 / 147 405 / 146 419 / 144 417 / 148 422 / 144 415 / 143
115 (45) 466 / 147 468 / 149 461 / 148 477 / 146 475 / 151 481 / 148 476 / 147
°F(°C)
2
RFC System - Liquid Line (+10 psig) / Vapor Line (+5 psig)
65 (18) 232 / 124 230 / 121 231 / 123 234 / 130 248 / 135 240 / 126 244 / 125
75 (24) 267 / 131 272 / 133 270 / 132 270 / 136 285 / 141 281 / 133 281 / 131
85 (29) 307 / 138 312 / 140 314 / 140 313 / 141 327 / 145 324 / 138 324 / 136
95 (35) 351 / 143 361 / 144 359 / 144 358 / 145 372 / 149 371 / 142 370 / 141
105 (41) 400 / 148 409 / 149 408 / 147 409 / 150 421 / 152 420 / 146 418 / 145
115 (46) 457 / 153 467 / 152 467 / 151 463 / 152 476 / 154 473 / 150 471 / 147
Table 4- Approach (APP) Values
3
- TXV System - ºF (ºC) +1ºF (0.5ºC)
65 (18) 4 (2.2) 5 (2.8) 4 (2.2) 5 (2.8) 6 (3.3) 7 (3.9) 8 (4.4)
75 (24) 5 (2.8) 6 (3.3) 5 (2.8) 5 (2.8) 8 (4.4) 8 (4.4) 9 (5.0)
85 (29) 6 (3.3) 6 (3.3) 6 (3.3) 6 (3.3) 8 (4.4) 8 (4.4) 9 (5.0)
95 (35) 5 (2.8) 7 (3.9) 6 (3.3) 6 (3.3) 8 (4.4) 8 (4.4) 9 (5.0)
105 (41) 3 (1.7) 6 (3.3) 6 (3.3) 5 (2.8) 8 (4.4) 8 (4.4) 9 (5.0)
115 (45) 3 (1.7) 6 (3.3) 6 (3.3) 6 (3.3) 8 (4.4) 9 (5.0) 9 (5.0)
Table 5- Subcooling (SC) Values
4
- TXV System - ºF (ºC) +1ºF (0.5ºC)
65 (18) 10 (5.6) 10 (5.6) 10 (5.6) 11 (6.1) 10 (5.6) 8 (4.4) 8 (4.4)
75 (24) 6 (3.3) 8 (4.4) 8 (4.4) 11 (6.1) 7 (3.9) 8 (4.4) 7 (3.9)
85 (29) 6 (3.3) 8 (4.4) 7 (3.9) 11 (6.1) 7 (3.9) 8 (4.4) 8 (4.4)
95 (35) 6 (3.3) 8 (4.4) 7 (3.9) 10 (5.6) 7 (3.9) 8 (4.4) 7 (3.9)
105 (41) 10 (5.6) 8 (4.4) 7 (3.9) 10 (5.6) 7 (3.9) 8 (4.4) 6 (3.3)
115 (46) 10 (5.6) 8 (4.4) 6 (3.3) 9 (5.0) 7 (3.9) 7 (3.9) 6 (3.3)
1 Typical pressures; indoor evaporator match up, indoor air quantity, and evaporator load will cause
the pressures to vary.
2 Temperature of air entering outside coil.
3 Approach = Liquid Line Temp. minus Outdoor Ambient Temperature
4 Subcooling = Saturation Temp. minus Liquid Line Temp Temperature
*2P1107* *P401289S*
11/07 401289S
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