Blower Compartment - Lennox LGA Series Unit Information

Units charged with R22
When liquid pressure rises to 275 +10 psig (1896 + 69
kPa), the switch closes and the condenser fan is ener-
gized. When discharge pressure in one refrigerant circuit
drops to 150 + 10 psig (1034 + 69 kPa), the switch opens
and the condenser fan in that refrigerant circuit is de−ener-
gized. This intermittent fan operation results in higher
evaporating temperature allowing the system to operate
without icing the evaporator coil and losing capacity.
Units charged with R410A
When liquid pressure rises to 450 ± 10 psig (3102 ± 69
kPa), the switch closes and the condenser fan is ener-
gized. When discharge pressure in one refrigerant circuit
drops to 240 ± 10 psig (1655 ± 69 kPa), the switch opens
and the condenser fan in that refrigerant circuit is de−ener-
gized. This intermittent fan operation results in higher
evaporating temperature allowing the system to operate
without icing the evaporator coil and losing capacity.
5−Low Pressure Switches S87, S88, S98, S97
The low pressure switch is an auto-reset SPST N.O.
switch (held N.C. by refrigerant pressure) which opens
on a pressure drop. All units are equipped with this
switch. The switch is located in the compressor suction
line.
S87 (compressor one), S88 (compressor two), S98
(compressor three), and S97 (compressor four) are
wired in series with the main control module A55.
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-strike counter, during first thermostat demand, before the
compressor is locked out. The control is reset by breaking and
remaking the thermostat demand or manually resetting the
control.
Units charged with R22
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), due to many causes such as refrig-
erant being added.
Units charged with R410A
When suction pressure drops to 40 + 5 psig (276 ± 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 90 + 5
psig (620 ± 34 kPa), due to many causes such as refrig-
erant being added.
6−Service Valve (optional all units)
Units may be equipped with service valves located in the
discharge and liquid lines. The service valves are manu-
ally operated valves used for service operation.
7−Filter Drier (all units)
All units have a filter drier located in the liquid line of each re-
frigerant circuit at the exit of each condenser coil. The drier
removes contaminants and moisture from the system.
8−Freezestats S49, S50, S53, S95
Each unit is equipped with a low temperature switch (freezes-
tat) located on the return bend of each evaporator coil. S49
(first circuit), S50 (second circuit), S53 (third circuit),
and S95 (fourth circuit) are located on the correspond-
ing evaporator coils.
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 re-
spective compressor until the coil warms sufficiently to
melt any accumulated frost.
If the freezestats are tripping frequently due to coil icing, check
the unit charge, airflow and filters before allowing unit back in
operation. Make sure to eliminate conditions which might pro-
mote evaporator ice buildup.
9−Condenser Fans B4, B5, B21, B22, B23, B24
See Specifications section in this manual for specifica-
tions of condenser fans used in LGA/LGC/LCA/LCC
units. All condenser fans used have single−phase motors.
All units are equipped with six condenser fans. The complete
fan assembly may be removed for servicing and cleaning
by removing the fan grill and turning the complete as-
sembly until the motor brackets line up with the notches
in the top panel. Lift the fan assembly out of the unit and
disconnect the jack plug located on the motor.
C−Blower Compartment
The blower compartment in all units is located between the
evaporator coil and the compressor / control section on the op-
posite side of the condenser coil. The blower assembly is ac-
cessed by disconnecting the blower motor jack plug J98/P98
(and all other plugs) and removing the screws on either side of
the sliding base. The base pulls out as shown in figure 12.
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