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The main control module A55 governs the low pressure
switches by shunting the switches during start up until pres-
sure is stabilized. After the shunt period, the control has a
three-strikecounter, during first thermostatdemand, before the
compressor is locked out. The control is reset by breaking and
remaking the thermostat demand or manually resetting the
control.
When suction pressure drops to 25 + 5 psig (172 ± 34
kPa) (indicating low pressure), the switch opens and the
compressor is de-energized. The switch automatically
resets when pressure in the suction line rises to 55 + 5
psig (379 ± 34 kPa).
7-Service Valves (optional on LGA/LCA units)
LGA/LCA units may be equipped with service valves lo-
cated in the discharge and liquid lines. The service
valves are manually operated valves used for service
operation.
8-Filter Drier (all units)
LGA/LCA units have a filter drier located in the liquid line of
each refrigerant circuit upstream of the TXV in the blower
compartment. The drier removes contaminants and mois-
ture from the system.
9-Freezestats S49 (all units)
Each unit is equipped with a low temperature switch (freezes-
tat) S49 located on a return bend of each evaporator coil.
Each freezestat is wired to the main control module A55.
Each freezestat is a SPST N.C. auto-reset switch which
opens at 29°F + 3°F (-1.7°C + 1.7°C) on a temperature drop
and closes at 58°F + 4°F (14.4°C + 2.2°C) on a tempera-
ture rise. To prevent coil icing, freezestats open during
compressor operation to temporarily disable the com-
pressoruntil thecoilwarmssufficientlytomeltany accu-
mulated frost.
If the freezestat is tripping frequently due to coil icing, checkthe
unit charge, airflow and filters before allowing unit back in op-
eration. Make sure to eliminate conditions which might pro-
mote evaporator ice buildup.
10-Condenser Fan B4 (all units)
Refer to Specifications section of this manual for speci-
fications of condenser fan B4 used in LGA/LCA units.
The condenser fan used is a single-phase motor. The fan
may be removed for servicing and cleaning by removing
the fan grill.
C-Blower Compartment
Overview
Units may be equipped with direct-drive or belt-drive blow-
ers. See unit nameplatefor blowertype.Direct driveblowers
will use a 3/4 hp. motor. Belt drive blowers will use a 1 1/2, 2
or 3 hp. motor.
Theblower housing in belt-drive models can be removed for
cleaningand inspection. In addition,removing blower allows
access to the heat exchanger tubes for inspection.
Line and low voltage make-up in all models is located in the
upper corner ofthe blowercompartment. Electrical entrance
is made through the base pan of the unit or through the cor-
ner mullion for horizontal position units. Lower voltage con-
nections can be accessed by removing the blower compart-
ment front panel. High voltage can be accessed through the
makeup box cover on corner mullion.
Access (Figure 8)
In all models, the blower can be accessed by removing the
unit front panel orend panel.In belt-drivemodels, the blower
motor can most easily be accessed by removing the blower
compartment end panel.
In all models, the evaporator coil, expansion valve and drain
pan can be accessed by removing the blower compartment
end panel.
1-Terminal Strip TB1
All units are equipped with a low voltage terminal strip (TB1)
located above the line voltage make-up box inside the blower
compartment. The strip is equipped with screw terminals
which are used for making all indoor thermostat and unit low
voltage control wiring connections.
2-Line Voltage Terminal Strip TB2
TB2 is a terminal strip which provides a means for connecting
all line voltage wiring. The strip is located in the line voltage
make-up box inside the blower compartment
3-Blower Wheel (all units)
All 3 to 6 ton (10.5 to 21 kW) LGA/LCA units have one 11 1/2
in. x 9 in. (292 to 228 mm) blower wheel.
4-Indoor Blower Motor B3 (all units)
All direct-drive LGA/LCA units use single-phase PSC motors.
Belt-drive units use single or three-phase motors (same as
supply voltage).
Single-phase Direct-drive 208/230V motors
Direct-drive motors are equipped with five speed taps for
adjusting blower speed. All motors are ball bearing type
and use a single capacitor (C4) located on the blower
housing.
Single-phase Direct-drive 460V motors
All LGA/LCA 460V and 575V units use a 460V single-phase
PSC blower motor. The motor has three cap-plugs (J38) for
adjusting blower speed. All motors are ball bearing type and
use a capacitor (C4) located on the blower housing.
The blower motor in 575V units uses an auto-transformer (T4)
to step-down 575V to 460V. T4 is located in the blower
compartment and is powered at all times.
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