Lennox LGM Series Manual page 16

PLUMBING, COMPRESSOR AND REFRIGERANT CIRCUITS DETAIL
Suction Line
Stage 2
Discharge Line
Stage 1
Discharge Line
Stage 2
Low Pressure Switch
S88
High Pressure
Switch
S7
High Pressure
Switch
S4
B-Cooling Components
Units use two separate refrigeration circuits. Circuit 1 uses
a variable speed compressor (B1) and Circuit two uses a
fixed speed scroll compressor (B2). The single evaporator
coil is row-split and return air first goes to circuit two before
passing through circuit one. A single condenser coil is used
that has interlaced circuits for circuit one and two. See fig­
ure 6. Units are equipped with a direct drive drive blower
which draws air across the evaporator during unit opera­
tion.
Suction Line
Stage 1
Compressor
B2
FIGURE 6
Page 16
Low Pressure Switch
Compressor
B1
Units are equipped with a single slab style evaporator. The
evaporator uses two thermostatic expansions valves.
Evaporators are equipped with enhanced fins and rifled
tubing.
In all units, each compressor is protected by a crankcase
heater, high pressure switch and low pressure switch. Ad­
ditional protection comes from the use of temperature sen­
sors that are located in the evaporator and condenser coils.
See sub section 10 for more details on location of of the
thermistors (temperature sensors) for added compressor
reliability.
Cooling may be supplemented by a factory‐ or field‐in­
stalled economizer.
Evaporator Coil
S87