Subcooling charging - TXV indoor
About this task:
The outdoor unit comes equipped with subcooling charts
optimized for that particular unit. Follow the instructions
on the unit. If those instructions are not readily available,
follow the instructions below.
1. Set the system running in cooling mode by setting
the thermostat at least 6°F below the room
temperature and operate the system for at least 10
min to 15 min.
2. Refer to the Technical Guide for the indoor airflow
and verify it is correct (it must be between 350
SCFM/ton and 400 SCFM/ton).
3. Measure and record the indoor wet bulb (WB) and
the outdoor ambient dry bulb (DB) temperature.
4. Using the charging chart located on the unit, find
the intersection of the indoor wet bulb and the
outdoor dry bulb. This is the recommended liquid
pressure (and subcooling value).
5. Measure and record the pressure at the liquid valve
pressure port and compare to the value obtained in
Step 4.
6. Add charge if the measured liquid pressure is lower
than the recommended value. Remove or recover
charge if the measured liquid pressure is above the
recommended value.
Example:
The liquid pressure listed at the intersection of
the indoor WB and the outdoor DB is 320 psig.
The pressure at the liquid valve is 305 psig. It is
necessary to add refrigerant to increase the liquid
pressure to 320 psig.
Note:
Condenser subcooling is obtained by
calculating the difference between the
saturated refrigerant temperature of the
pressure measured at the liquid base valve
and the liquid tube temperature as measured
at the liquid base valve.
Subcooling Temperature (TC) = Saturated
Temperature (TS) – Liquid Temperature (T)
CAUTION
It is unlawful to knowingly vent, release, or
discharge refrigerant into the open air during
repair, service, maintenance, or the final
disposal of this unit.
R-410A saturation properties
Table 2: R-410A saturation properties
Temperature Pressure Temperature Pressure Temperature Pressure Temperature Pressure Temperature Pressure
°F psig °F psig °F psig °F psig °F psig
45 130 60 170 75 217 90 274 105 341
46 132 61 173 76 221 91 278 106 345
47 135 62 176 77 224 92 282 107 350
48 137 63 179 78 228 93 287 108 355
49 140 64 182 79 232 94 291 109 360
50 142 65 185 80 235 95 295 110 365
51 145 66 188 81 239 96 299 111 370
52 147 67 191 82 243 97 304 112 375
53 150 68 194 83 247 98 308 113 380
54 153 69 197 84 250 99 313 114 385
55 156 70 201 85 254 100 317 115 391
56 158 71 204 86 258 101 322 116 396
57 161 72 207 87 262 102 326. 117 401
58 164 73 211 88 266 103 331 118 407
59 167 74 214 89 270 104 336 119 412
Installation Manual: R-410A Outdoor Split-System Air Conditioner 15
Johnson Controls Ducted Systems
To Next Page
Loading...
Need help?
General
