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LGH/LCH036, 048, 060, 072, 074
D-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 - On Ultra high efficiency units, use Unit Controller
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 20 through
32 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.
E-Charge Verification - Fin/Tube Coil - AHRI TESTING
Approach Method -
Standard and High Efficiency Units
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 33.
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 tables 20 through 32 as
a guide for typical operating pressures.
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 Unit
Controller 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 34. A subcooling temperature greater than this
value indicates an overcharge. A subcooling
temperature less than this value indicates an
undercharge.
TABLE 20
LG/LC 036S/H NORMAL OPERATING PRESSURES
Outdoor Coil
Entering Air Temp
Discharge
+
10 psig
Suction + 5
psig
655 F 265 140
755 F 299 143
855 F 348 145
955 F 394 148
1055 F 445 150
1155 F 500 153
TABLE 21
LG/LC 036S/H REHEAT NORMAL OPERATING
PRESSURES
Outdoor Coil
Entering Air Temp
Discharge
+
10 psig
Suction + 5
psig
655 F 262 139
755 F 300 141
855 F 342 144
955 F 388 148
1055 F 437 150
1155 F 491 153
TABLE 22
LG/LC 036U NORMAL OPERATING PRESSURES
Outdoor Coil
Entering Air Temp
Discharge
+
10 psig
Suction + 5
psig
655 F 238 146
755 F 277 149
855 F 317 150
955 F 363 151
1055 F 416 151
1155 F 474 154
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