Lennox LGT092H Installation Instructions Manual page 19

D-Refrigerant Charge and Check
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.
If weighing facilities are not available, or to check the
charge, use the following procedure:
IMPORTANT - Charge unit in standard cooling mode
at full load..
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.
Mobile service app:
Test>Cooling>Cooling Stage 3.
2- Check each system separately with all stages
operating. Compare the normal operating pressures
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 charging curve to
determine a target liquid temperature.
RTU Menu>Component
NOTE - Pressures are listed for sea level applications.
4- Use the same thermometer to accurately measure
the liquid temperature (in the outdoor section).
S If measured liquid temperature is higher than the
target liquid temperature, add refrigerant to the
system..
S If measured liquid temperature is lower than the
target
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: 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.
Page 19
liquid temperature, recover
process until measured
agrees with the
some
liquid
target liquid