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LGM/LCM036, 048, 060, 074
Cooling Start-Up
A-Operation
1- Initiate full load cooling operation using the following
mobile service app menu path:
SERVICE > TEST > COOL > COOL 3
(COOL 4 on 074U units)
Note - Refer to Cooling Operation section for ultra 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 - Fin/Tube 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- Attach gauge manifolds and operate unit in cooling
mode on
HIGH SPEED
with economizer disabled
until system stabilizes (approximately five minutes).
Make sure outdoor air dampers are closed.
Note - Use mobile service app menu path SERVICE >
TEST > COOL > COOL 3 for 036, 048 and 060U units.
Use COOL 4 for 074U units.
2- Use a thermometer to accurately measure the
outdoor ambient temperature.
3- Apply the outdoor temperature to tables 5 through 8
to determine normal operating pressures. Pressures
are listed for sea level applications at 80°F dry bulb
and 67°F wet bulb return air.
4- 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.
5- If discharge pressure is high, remove refrigerant from
the system. If discharge pressure is low, add
refrigerant to the system.
Add or remove charge in increments.
Allow the system to stabilize each time
refrigerant is added or removed.
6- Use one of the following charge verification methods
along with the normal operating pressures to confirm
readings.
Subcooling Method - Ultra High Efficiency Units
1- Attach gauge manifold to the liquid line. With the
economizer disabled, operate the unit in
cooling
mode at high speed
using the following mobile
service app menu path:
SERVICE > TEST > COOL > COOL 3
(COOL 4 on 074U units)
2- Use the liquid line pressure and a PT chart to
determine the saturated liquid temperature.
3- Measure the liquid line temperature at the condenser
outlet.
Subcooling Temperature = Liquid Saturated
Temperature Minus Liquid Temperature.
4- The subcooling temperature should be as shown in
figure 9. A subcooling temperature greater than this
value indicates an overcharge. A subcooling
temperature less than this value indicates an
undercharge.
TABLE 5 581009-01
LG/LC 036SU NORMAL OPERATING PRESSURES
Outdoor Coil
Entering Air Temp
Discharge
+10 psig
S 5
psig
65
5
F
232
146
75
5
F
267
149
85
5
F
307
150
95
5
F
351
151
105
5
F
400
151
115
5
F
454
154
