Lennox LGH094U Unit Information page 54

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 21 through 23
to determine normal operating pressures. Pressures
are listed for sea level applications at 80
5
and 67 F 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.
Outdoor Coil
Entering Air
Temp
655 F
755 F
855 F
955 F
1055 F
1155 F
Outdoor Coil
Entering Air
Temp
655 F
755 F
855 F
955 F
1055 F
1155 F
Outdoor Coil
Entering Air
Temp
655 F
755 F
855 F
955 F
1055 F
1155 F
Charge Verification - Approach Method - AHRI Testing
(Fin/Tube Coil Continued)
5
F dry bulb
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
24. 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 tables21 through23 as a
guide for typical operating pressures.
APPROACH TEMPERATURE - 094, 122, 152
Unit
094
122, 152
Page 54
TABLE 21
LGH/LCH094U
Discharge +10
Suction +5 psig
psig
238 136
273 141
313 143
361 146
396 149
448 152
TABLE 22
LGH/LCH122U
Discharge +10
Suction +5 psig
psig
250 134
288 138
331 141
378 143
412 144
463 147
TABLE 23
LGH/LCH152U
Discharge +10
Suction +5 psig
psig
266 129
305 132
346 134
391 138
443 141
498 143
TABLE 24
Liquid Temp. Minus Ambient Temp.
Full Load (Both Compressors)
5°F + 1 (2.8°C + 0.5)
4°F + 1 (2.2°C + 0.5)