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LGT/LCT036, 048, 060, 072
Cooling Start-Up
A-Operation
1- Initiate full load cooling operation using the following
mobile service app menu path:
RTU MENU > COMPONENT TEST > COOLING >
COOLING STAGE 2
Note - Refer to Cooling Operation section for high
efficiency unit operation in zone sensor mode.
2- Units contain one refrigerant circuit or stage.
3- Unit is charged with R-410A refrigerant. See unit
rating plate for correct amount of charge.
4- Refer to Cooling Operation and Adjustment section for
proper method to check refrigerant charge.
B-Refrigerant Charge and Check - All-Aluminum Coil
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:
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 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.
Note - Pressures are listed for sea level applications.
4- Use the same thermometer to accurately measure the
liquid temperature (in the outdoor section).
If measured liquid temperature is higher than the
target liquid temperature, add refrigerant to the
system.
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 process until measured liquid
temperature agrees with the target liquid
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 97°F. For a measured liquid
temperature of 106°F, add charge in increments until
measured liquid temperature agrees with the target
liquid temperature.
