Lennox LCH036 Installation Instructions Manual page 82

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,
reclaim the charge, evacuate the system, and add
required nameplate charge.
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
5
80 F dry bulb and 67
5- Compare the normal operating pressures to the
pressures 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
normal operating pressures to confirm readings.
This unit is equipped with
5
F wet bulb return air.
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)
1- Using the same thermometer, compare liquid
temperature to outdoor ambient temperature.
Approach Temperature = Liquid temperature (at
condenser outlet) minus ambient temperature.
2- Approach temperature should match values in table
17. An approach temperature greater than value
shown indicates an undercharge. An approach
temperature less than value shown indicates an
overcharge.
3- The approach method is not valid for grossly over or
undercharged systems. Use tables19 through21 as
a guide for typical operating pressures.
APPROACH TEMPERATURE - 094, 122, 152
Unit
094
122, 152
Page 32
TABLE 19
LGH/LCH094U
Discharge +10
Suction +5 psig
psig
238
273
313
361
396
448
TABLE 20
LGH/LCH122U
Discharge +10
Suction +5 psig
psig
250
288
331
378
412
463
TABLE 21
LGH/LCH152U
Discharge +10
Suction +5 psig
psig
266
305
346
391
443
498
TABLE 22
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)
136
141
143
146
149
152
134
138
141
143
144
147
129
132
134
138
141
143