Approach Temperature; Kgb/Kcb024 Normal Operating Pressures - Lennox KGB024 Installation Instructions Manual

TABLE 12
KGA 060S -5 & HIGHER; KCA 060S -4 & HIGHER
NORMAL OPERATING PRESSURES
Outdoor Coil
Entering Air Temp
65
75
85
95
105
115
D-Charge Verification-Approach Method--Fin/Tube Coils
KGA/KCA 036-060 Units
1- Using the same thermometer, compare liquid
temperature to outdoor ambient temperature.
Approach Temperature = Liquid temperature minus
ambient temperature.
2- Approach temperature should match values in table
13. An approach temperature greater than value
shown indicates an undercharge. An approach
temperature less than value shown indicates an
overcharge.
3- Do not use the approach method if system pressures
do not match pressures in tables 7 through 12. The
approach method is not valid for grossly over or
undercharged systems.
TABLE 13

APPROACH TEMPERATURE

Unit Liquid Temp. Minus Ambient Temp.
036S
048S
060S
E-Refrigerant Charge and Check - All-Aluminum Coil
KGA/KCA 072, 090 & KGB/KCB024-074
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.
65 °F
Suct Disc Suct
(psig) (psig) (psig)
118 224 119
125 227 127
141 232 144
159 236 164
KG/KC 024, 030, 036, 048, 060, 072, 074, 090
Discharge Suction + 5
+10 psig psig
279 130
317 135
359 139
404 143
454 143
508 143
7°F + 1 (3.9°C + 0.5)
11°F + 1 (6.1°C + 0.5)
6°F + 1 (3.3°C + 0.5)

KGB/KCB024 Normal Operating Pressures

Outdoor Coil Entering Air Temperature
75 °F 85 °F
Disc Suct Disc
(psig) (psig) (psig)
259 121 297
262 129 301
267 149 306
273 168
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- Compare the normal operating pressures (see table
14 through 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
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 KG/KC 090: At 95°F outdoor ambient and
a measured suction pressure of 130psig, the target
liquid temperature is 99°F. For a measured liquid
temperature of 106°F, add charge in increments
until measured liquid temperature agrees with the
target liquid temperature.
TABLE 14
95 °F
Suct Disc
(psig) (psig)
121 342
130 343
151 347
311 171 354
Page 44
process until measured
agrees with the target
105 °F 115 °F
Suct Disc Suct
(psig) (psig) (psig)
122 390 124
131 391 134
153 393 154
173 400 176
liquid
liquid
Disc
(psig)
442
441
444
449