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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
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