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G-Refrigerant Charge and Check - Fin/Tube Coil & TXV
LGH/LCH094U, 122U, 152U
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, re
claim the charge, evacuate the system, and add required
nameplate charge. This unit is equipped with solenoid valves
which do not allow refrigerant flow between the high side and
the low side when the unit is de-energized. When reclaiming/
evacuating the system, make sure refrigerant/vacuum is
pulled from both the suction and discharge lines. When adding
nameplate charge, add 1/3 to the suction line and 2/3 to the
discharge line.
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- Attach gauge manifolds and operate unit in cooling
mode with economizer disabled until system stabilizes
(approximately five minutes). Make sure outdoor air
dampers are closed.
2- Make sure both compressors are operating.
3- Use a thermometer to accurately measure the outdoor
ambient temperature.
4- Apply the outdoor temperature to tables 19 through 21
to determine normal operating pressures. Pressures
are listed for sea level applications at 80
5F dry bulb
and 67
5F wet bulb return air.
5- Compare the normal operating pressures to the pres
sures obtained from the gauges. Minor variations in
these pressures may be expected due to differences in
installations. Significant differences could mean that
the system is not properly charged or that a problem
exists with some component in the system. Correct
any system problems before proceeding.
6- If discharge pressure is high, remove refrigerant from
the system. If discharge pressure is low, add refrigerant
to the system.
S Add or remove charge in increments.
S Allow the system to stabilize each time refrigerant
is added or removed.
7- Use the following approach method along with the nor
mal operating pressures to confirm readings.
TABLE 19
LGH/LCH094U
Outdoor Coil
Entering Air
Temp
Discharge +10
psig
Suction +5 psig
655 F 238 136
755 F 273 141
855 F 313 143
955 F 361 146
1055 F 396 149
1155 F 448 152
TABLE 20
LGH/LCH122U
Outdoor Coil
Entering Air
Temp
Discharge +10
psig
Suction +5 psig
655 F 250 134
755 F 288 138
855 F 331 141
955 F 378 143
1055 F 412 144
1155 F 463 147
TABLE 21
LGH/LCH152U
Outdoor Coil
Entering Air
Temp
Discharge +10
psig
Suction +5 psig
655 F 266 129
755 F 305 132
855 F 346 134
955 F 391 138
1055 F 443 141
1155 F 498 143
Charge Verification - Approach Method - AHRI Testing
(Fin/Tube Coil Continued)
1- Using the same thermometer, compare liquid tempera
ture to outdoor ambient temperature.
Approach Temperature = Liquid temperature (at con
denser outlet) minus ambient temperature.
2- Approach temperature should match values in table
22. An approach temperature greater than value
shown indicates an undercharge. An approach tem
perature less than value shown indicates an over
charge.
3- The approach method is not valid for grossly over or
undercharged systems. Use tables19 through21 as a
guide for typical operating pressures.
TABLE 22
APPROACH TEMPERATURE - 094, 122, 152
Unit
Liquid Temp. Minus Ambient Temp.
Full Load (Both Compressors)
094 5°F + 1 (2.8°C + 0.5)
122, 152 4°F + 1 (2.2°C + 0.5)
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