Lennox Signature XP21 Series Installation And Service Procedure page 66

CRANKCASE HEATER (HR1)
Compressors in all units are equipped with a 70 watt belly-
band type crankcase heater. HR1 prevents liquid from
accumulating in the compressor. HR1 is controlled by the
crankcase heater thermostat.
CRANKCASE HEATER THERMOSTAT (S40)
Thermostat S40 controls the crankcase heater in all units.
S40 is located on the liquid line. When liquid line tempera-
ture drops below 50°F the thermostat S40 closes
energizing HR1. The thermostat will open, de−energizing
HR1 once liquid line temperature reaches 70°F .
SOLENOID
TO COMPRESSOR
DISCHARGE LINE
LINE TO OUTDOOR
COIL
SUCTION LINE (TO
COMPRESSOR)
VAPOR LINE (TO SERVICE VALVE)
IMPORTANT CONFIRM CORRECT CONNECTIONS OF
REFRIGERANT LINES TO REVERSING VALVE BEFORE
BRAZING IN VALVE.
XP21
IMPORTANT
VALVE.
Figure 33. Typical Reversing Valve Components and Operation
REVERSING VALVE (L1)
The primary components of the reversing valve are revers-
ing valve, solenoid and wiring harness.
ENSURE NEW REVERSING VALVE IS INSTALL EXACTLY AS ORIGINAL
1. WHEN THE SOLENOID IS ENERGIZED (ON), THE
EVAPORATOR (INDOOR COIL
PRESSURE IS DIRECTED TO THE SUCTION (S) BACK
TO THE COMPRESSOR.
2. WHEN THE SOLENOID IS DE−ENERGIZED (OFF),
REFRIGERANT PRESSURE IS DIRECTED FROM THE
CONDENSER (OUTDOOR COIL (C) TO THE SUCTION
(S) BACK TO THE COMPRESSOR.
Page 66
REVERSING VALVE
OPERATION
E) REFRIGERANT