Lennox LCH036 Installation Instructions Manual page 80

F-Refrigerant Charge and Check - Fin/Tube Coil & RFC
LGH/LCH092H, 102H, 120H, 150S
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 table 18) 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
65 F
Suct
(psig)
108
114
Circuit 1
119
125
108
115
Circuit 2
124
131
LGH/LCH150S Normal Operating Pressures - Fin/Tube - RFC
75 F
Disc Suct Disc
(psig) (psig) (psig)
253 112 295
255 119 296
257 129 303
264 136 308
273 111 314
277 119 318
284 131 327
289 140 334
charging curve 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
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/LCH150 Circuit 1: At 95°F outdoor
ambient and a measured suction pressure of
130psig, the target liquid temperature is 96°F. For a
measured liquid temperature of 106°F, add charge in
increments until measured liquid temperature agrees
with the target liquid temperature.
TABLE 18
Outdoor Coil Entering Air Temperature
85 F 95 F
Suct Disc Suct
(psig) (psig) (psig)
114 338 117
122 342 125
136 348 141
146 358 155
114 356 117
122 362 125
137 372 141
148 382 155
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the process until measured
agrees with the
105 F
Disc Suct Disc
(psig) (psig) (psig)
384 119 438
390 127 444
403 145 460
413 161 470
400 119 451
409 128 460
422 145 474
434 160 486
liquid
target liquid
115 F
Suct Disc
(psig) (psig)
122 501
129 501
149 522
167 530
121 508
129 512
147 532
163 541