COOLING ONLY PROCEDURE
Units with Cooling Mode TXV
Units installed with cooling mode TXV require charging by the
subcooling method.
1. Operate unit a minimum of 10 minutes before checking
charge.
2. Measure liquid service valve pressure by attaching an accurate
gage to service port.
3. Measure liquid line temperature by attaching an accurate
thermistor type or electronic thermometer to liquid line near
outdoor coil.
4. Refer to unit rating plate for required subcooling temperature.
5. Refer to Table 3. Find the point where required subcooling
temperature intersects measured liquid service valve pressure.
6. To obtain required subcooling temperature at a specific liquid
line pressure, add refrigerant if liquid line temperature is
higher than indicated or reclaim refrigerant if temperature is
lower. Allow a tolerance of ± 3°F.
Units with Indoor Pistons
Units installed with indoor pistons require charging by the super-
heat method.
The following procedure is valid when indoor airflow is within
± 21 percent of its rated CFM.
1. Operate unit a minimum of 10 minutes before checking
charge.
2. Measure suction pressure by attaching an accurate gage to
suction valve service port.
3. Measure suction temperature by attaching an accurate ther-
mistor type or electronic thermometer to suction line at service
valve.
4. Measure outdoor air dry-bulb temperature with thermometer.
5. Measure indoor air (entering indoor coil) wet-bulb tempera-
ture with a sling psychrometer.
6. Refer to Table 4. Find outdoor temperature and evaporator
entering air wet-bulb temperature. At this intersection, note
superheat.
7. Refer to Table 5. Find superheat temperature located in item 6
and suction pressure. At this intersection, note suction line
temperature.
8. If unit has a higher suction line temperature than charted
temperature, add refrigerant until charted temperature is
reached.
9. If unit has a lower suction line temperature than charted
temperature, reclaim refrigerant until charted temperature is
reached.
10. When adding refrigerant, charge in liquid form into suction
service port using a flow-restricting device.
11. If outdoor air temperature or pressure at suction valve
changes, charge to new suction line temperature indicated on
chart.
Table 3—Required Liquid-Line Temperature (°F)
LIQUID
PRESSURE AT
SERVICE VALVE
(PSIG)
REQUIRED SUBCOOLING
TEMPERATURE
(°F)
8 1012141618
189 58 56 54 52 50 48
195 60 58 56 54 52 50
202 62 60 58 56 54 52
208 64 62 60 58 56 54
215 66 64 62 60 58 56
222 68 66 64 62 60 58
229 70 68 66 64 62 60
236 72 70 68 66 64 62
243 74 72 70 68 66 64
251 76 74 72 70 68 66
259 78 76 74 72 70 68
266 80 78 76 74 72 70
274 82 80 78 76 74 72
283 84 82 80 78 76 74
291 86 84 82 80 78 76
299 88 86 84 82 80 78
308 90 88 86 84 82 80
317 92 90 88 86 84 82
326 94 92 90 88 86 84
335 96 94 92 90 88 86
345 98 96 94 92 90 88
354 100 98 96 94 92 90
364 102 100 98 96 94 92
374 104 102 100 98 96 94
384 106 104 102 100 98 96
395 108 106 104 102 100 98
406 110 108 106 104 102 100
416 112 110 108 106 104 102
427 114 112 110 108 106 104
439 116 114 112 110 108 106
450 118 116 114 112 110 108
462 120 118 116 114 112 110
474 122 120 118 116 114 112
486 124 122 120 118 116 114
499 126 124 122 120 118 116
511 128 126 124 122 120 118
7
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