Page 17
3 − Compare stabilized pressures with those provided in
table 7, Normal Operating Pressures." Minor varia-
tions in these pressures may be expected due to differ-
ences in installations. Significant differences could
mean that the system is not properly charged or that a
problem exists with some component in the system.
Pressures higher than those listed indicate that the
system is overcharged. Pressures lower than those
listed indicate that the system is undercharged. Verify
adjusted charge using the approach method.
Approach Method
4 − Use the same digital thermometer used to check out-
door ambient temperature to check liquid line tempera-
ture. Verify the unit charge using the approach method.
The difference between the ambient and liquid temper-
atures should match values given in table 6. Add refrig-
erant to lower the approach temperature and remove it
to increase the approach temperature. Loss of charge
results in low capacity and efficiency.
5 − If the values do not agree with the those in table 6, add
refrigerant to lower the approach temperature or re-
cover refrigerant from the system to increase the ap-
proach temperature.
Table 6
Approach Values for Charging
Model Number Approach Temperature
Liquid Line Temp. − Outdoor Ambient °F (°C)
HPXA12−18 5 (2.8)
HPXA12−24 8.0 (4.4)
HPXA12−30 12.5 (6.9)
HPXA12−36 13 (7.2)
HPXA12−42 13 (7.2)
HPXA12−48 8.5 (4.7)
HPXA12−60 12 (6.7)
IMPORTANT
Use table 7 as a general guide when performing
maintenance checks. This is not a procedure for
charging the unit (Refer to Charging/Checking
Charge section). Minor variations in these pressures
may be expected due to differences in installations.
Significant differences could mean that the system
is not properly charged or that a problem exists with
some component in the system.
Table 7
Normal Operating Pressures
(Liquid ±10 and Vapor ±5 psig)
Cooling Operation
Outdoor Coil
HPXA12−18
HPXA12−24 HPXA12−30 HPXA12−36 HPXA12−42 HPXA12−48 HPXA12−60
Entering Air
Tem
. °F
°C
Liquid Vapor
Liquid vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor
65 (18.3)
223 147
254 130 244 136 262 135 260 133 240 126 250 123
75 (23.9)
270 149
290 134 282 139 304 138 300 135 280 130 300 132
85 (29.4)
312 150
335 137 325 141 349 141 345 137 320 134 345 137
95 (35.0)
360 152
382 140 375 143 399 143 397 139 360 136 378 140
105 (40.6)
406 154
433 143 426 145 454 146 452 142 415 137 430 142
115 (46.1)
463 155
490 146 485 147 514 149 510 145 470 139 497 145
Heating Operation
Outdoor Coil
HPXA12−18
HPXA12−24 HPXA12−30 HPXA12−36 HPXA12−42 HPXA12−48 HPXA12−60
Entering Air
Tem
. °F
°C
Liquid Vapor
Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor
20 (−6.6)
265 63
295 59 340 60 278 59 288 60 315 60 282 57
30 (−1.1)
280 78
315 72 350 75 290 72 297 70 325 74 300 70
40 (4.4)
294 96
335 87 362 90 305 89 310 85 340 90 310 82
50 (10.0)
310 112
350 103 374 110 317 105 325 105 360 106 325 92
60 (15.5)
320 133
375 120 390 132 333 128 344 127 380 128 335 100
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