Page 31
SGH/SCH036, 060, 120, 240
Cooling Operation and Adjustments
A-Refrigerant Charge and Check
WARNING
Do not exceed nameplate charge under any condi
tion.
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 15 - 21) 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
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 the process until measured liquid
temperature agrees with the target liquid temperature.
Do not go below the target liquid temperature when
adjusting charge. Note that suction pressure can
change as charge is adjusted.
7- Example: SG/SC 240 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 15
SG/SC 036 Normal Operating Pressures - No Reheat - 580971-01
Outdoor Coil Entering Air Temperature
65
°
F
75
°
F
85
°
F
95
°
F
105
°
F
115
°
F
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
120
229
117
269
122
316
125
363
127
418
130
488
128
230
131
268
132
313
134
361
135
417
138
482
147
239
147
273
152
314
154
360
158
413
161
474
165
254
167
282
172
325
174
368
176
424
180
489
TABLE 16
SG/SC 036 Normal Operating Pressures - Reheat - 580979-01
Outdoor Coil Entering Air Temperature
65
°
F
75
°
F
85
°
F
95
°
F
105
°
F
115
°
F
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
113
246
114
293
113
363
115
439
119
534
125
561
121
249
125
276
124
352
125
423
129
475
133
540
136
264
143
288
147
324
148
380
151
440
152
514
154
278
160
307
168
339
171
382
174
439
176
507
