Lennox LGT156H Installation Instructions Manual page 22

EVAPORATOR COIL
(not to scale)
CIRCUITS
1 & 2
INTERTWINED
CIRCUITS 3 & 4
INTERTWINED
D-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:
IMPORTANT - Charge unit in normal cooling mode.
1- Attach gauge manifolds to discharge and suction
lines. 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 4
2- Use a thermometer to accurately measure the
outdoor ambient temperature.
3- Apply the outdoor temperature to tables 4 through 13
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
LGT/LCT156, 180, 210, 240, 300
210, 240, 300 REFRIGERANT CIRCUITS
ALL FOUR EVAPORATOR
COIL CIRCUITS ARE
INTERTWINED
FIGURE 20
E-Charge Confirmation and Fine Tuning - Liquid
Temperature Check
Note - Pressures are listed for sea level applications.
Page 22
CONDENSER COIL
CIRCUIT 3 & 4
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.
S Add or remove charge in increments.
S Allow the system to stabilize each time
refrigerant is added or removed.
6- Confirm charge amount using liquid temperature
plots. Fine tune charge amount(s) to match liquid
temperature plots as needed per the next section.
1- Use the same thermometer to accurately measure the
liquid temperature (in the outdoor section).
D If measured liquid temperature is higher than the
target liquid temperature, add refrigerant to the
system.
D
If measured liquid temperature is lower than the
target liquid temperature, recover some refrigerant from
the system.
CONDENSER COIL
CIRCUIT 1 & 2