Lennox LGM Series Manual page 20

A192
INVERTER
208/230V INVERTER
BOARD SHOWN
W V U
B1
COMPRESSOR
INVERTER HEAT SINK
P47
FIGURE 9
INVERTER WIRE ROUTING
T61
TRANSFORMER
T
S
R
High voltage enters
the compressor
L43
here.
REACTOR
FIGURE 8
3-Crankcase Heaters HR1, HR2
All LGM units use insertion type heaters. Heater HR1 is in­
stalled around compressor B1 and heater HR2 is installed
around compressor B2. Crankcase heater wattage varies
by compressor size. Power to crankase heater (HR1) is
controlled through the K191 relay and power to HR2 con­
trolled by auxiliary contact on K2 compressor contactor that
is normally closed.
B47 4-High Pressure Switches S4, S7
The high pressure switch is an auto‐reset SPST N.C. which
open on a pressure rise. The switch is located in the com­
pressor discharge line and is wired to the both the compres­
sor contactor via controller A55. S4 protects compressor
B1 and S7 protects compress B2. S4 is wired to the K1 con­
tactor that disables power to the A192 Compressor Vari­
able Speed Inverter. S7 is wired to the K2 contactor that
dissables the B2 compressor.
When discharge pressure rises to 640 ± 10 psig (4413 ± 69
kPa) (indicating a problem in the system) the switch opens
and the respective compressor is de-energized (the econo­
mizer can continue to operate). When discharge pressure
drops to 475 ± 20 psig (3275 ± 138 kPa) the pressure switch
will close.
The A55 Unit Controller has a three-strike counter before
locking out. This means the control allows three high pres­
sure trips per one thermostat demand. The control can be
reset by breaking and remaking the thermostat demand or
manually resetting the control.
Page 20
T
S
R
FL1
FILTER BOARD
R S T
High voltage en­
ters the filter board
here.