Refrigerant Charge And Check - All-Aluminum Coils; Normal Operating Pressures - Lennox LGH180H Installation Instructions Manual

D-Refrigerant Charge and Check - All-Aluminum Coils
WARNING-Do not exceed nameplate charge under
any condition.
This unit is factory charged and should require no further
adjustment. If the system requires additional refrigerant,
reclaim the charge, evacuate the system, and add
required nameplate charge.
NOTE - System charging is not recommended below
60_F (15_C). In temperatures below 60_F (15_C), the
charge must be weighed into the system.
If weighing facilities are not available, or to check the
charge, use the following procedure:
IMPORTANT - Charge unit in standard cooling mode.
1- Make sure outdoor coil is clean. Attach gauge
manifolds and operate unit at full CFM in cooling mode
with economizer disabled until system stabilizes
(approximately five minutes). Make sure all outdoor air
dampers are closed.
2- Check each system separately with all stages
operating. Compare the normal operating pressures
(see tables 4 - 8) to the pressures obtained from the
gauges. Check unit components if there are
significant differences.
3- Measure the outdoor ambient temperature and the
suction pressure. Refer to the appropriate circuit
LGH/LCH156H NORMAL OPERATING PRESSURES - ALUMINUM COIL
65 °F
Suct Disc
(psig) (psig)
110 241
118 245
Circuit 1
137 255
154 266
111 249
119 253
Circuit 2
137 263
153 276
115 256
123 261
Circuit 3
140 273
157 284
TABLE 4

Normal Operating Pressures

Outdoor Coil Entering Air Temperature
75 °F 85 °F
Suct Disc Suct
(psig) (psig) (psig)
112 279 115
121 282 124
140 292 142
160 304 163
112 287 113
120 291 122
139 301 142
158 313 162
116 294 118
125 299 128
143 311 146
162 324 166
charging curve on Page 26 through Page 35 to
determine a target liquid temperature.
Note - Pressures are listed for sea level applications.
4- Use the same thermometer to accurately measure the
liquid temperature (in the outdoor section).
D If measured liquid temperature is higher than
the target liquid temperature, add refrigerant to
the system.
D If measured liquid temperature is lower than
the target liquid temperature, recover some
refrigerant from the system.
5- Add or remove charge in increments. Allow the system
to stabilize each time refrigerant is added or removed.
6- Continue the
temperature
temperature. Do not go below the target liquid
temperature when adjusting charge. Note that
suction pressure can change as charge is adjusted.
7- Example LGH/LCH180H Circuit 1: At 95°F outdoor
ambient and a measured suction pressure of
130psig, the target liquid temperature is 96.5°F. For
a measured liquid temperature of 106°F, add charge
in increments until measured liquid temperature
agrees with the target liquid temperature.
95 °F
Disc Suct Disc
(psig) (psig) (psig)
321 117 367
324 127 370
333 145 378
346 163 392
328 116 374
332 124 378
342 145 387
356 164 402
335 120 381
340 130 386
353 149 398
367 169 413
Page 23
process until measured
agrees with the target
105 °F
Suct Disc Suct
(psig) (psig) (psig)
119 419 122
129 420 131
148 431 152
171 441 174
118 423 121
127 428 129
146 438 149
167 451 171
122 429 124
132 436 133
152 449 154
171 462 174
507124-04
liquid
liquid
115 °F
Disc
(psig)
472
474
484
496
474
481
490
505
480
488
502
515
3/2016