Lennox XP16 Series Unit Information page 49

Cooling
A – First Stage Low Capacity
Transformer from indoor unit supplies 24VAC power to
the thermostat and outdoor unit controls.
1− Internal wiring energizes terminal O by cooling mode
selection, energizing the reversing valve. Cooling
demand initiates at Y1 in the thermostat.
2 − The defrost board checks for open low or high−pressure
switches and proper coil, ambient and discharge sensor
readings.
If checks show no issues, the defrost board sends
D
24 volts through Y1 OUT signal to the K1
compressor contactor coil.
XP16−060−05 only − defrost board sends 24 volts
D
through Y1 OUT signal to the yellow wire to the
outdoor fan motor.
HARD START KIT IF USED − Compressor begins start up.
Relay K31 remains closed during start up and capacitor C7
remains in the circuit. As compressor speeds up K31 is
energized, de−energizing capacitor C7.
3− K1−1 N.O. closes energizing compressor B1 and
outdoor fan motor B4.
4− Solenoid L34 is NOT energized.
The slider ring remains open limiting compressor
D
to low capacity.
XP16−060−05 only − The 24 volt input on the
D
yellow wire to the outdoor fan motor will allow it to
run on low speed.
B – Second Stage High Capacity
5− Second stage thermostat demand goes through Y2 on
the defrost board and energizes rectifier plug D4. D4
converts the AC voltage to DC voltage and energizes
L34 unloader solenoid.
L34 then closes the slider ring, allowing the
D
compressor to operate at high capacity.
XP16−060−05 only − The 24 volt input to the
D
yellow and blue wires of the outdoor fan will
provide high speed operation.
Heating
A – Low Capacity
1− Internal wiring de−energizes terminal O by heating mode
selection, de−energizing the reversing valve. Heating
demand initiates at Y1 in the thermostat.
2 − The defrost board checks for open low or high−pressure
switches and proper coil, ambient and discharge sensor
readings.
XP16
Sequence of Operation XP16−024/060
Page 49
If checks show no issues, the defrost board sends
D
24 volts through Y1 OUT signal to the K1
compressor contactor coil.
XP16−060−05 only − defrost board sends 24 volts
D
through Y1 OUT signal to the yellow wire to the
outdoor fan motor.
HARD START KIT IF USED − Compressor begins start up.
Relay K31 remains closed during start up and capacitor C7
remains in the circuit. As compressor speeds up K31 is
energized, de−energizing capacitor C7.
3− K1−1 closes, energizing the compressor and outdoor fan
motor.
4− Solenoid L34 is NOT energized. The slider ring remains
open limiting compressor to low capacity.
B – High Capacity (Ambient temperature above
defrost board Y2 lock−in temperature)
1− Room thermostat in heating mode. Room thermostat
outputs Y1 and Y2 (if applicable to that room thermostat)
signal to the defrost board in the heat pump and to the
indoor unit.
2− The defrost board checks for open low or high−pressure
switches and proper coil, ambient and discharge sensor
readings.
D If checks show no issues, the defrost board sends
24 volts through Y1 OUT signal to the K1
compressor contactor coil.
XP16−060−05 only − defrost board sends 24 volts
D
through Y1 OUT signal to the yellow wire to the
outdoor fan motor.
3 − The defrost board sends:
24 volts through Y2 OUT to the L34 compressor
D
solenoid plug.
XP16−060−05 only − 24 volts through Y2 OUT to
D
the blue wire to the outdoor fan motor.
The 2− wire compressor solenoid plug converts the 24volt
AC outputs to a 24volt DC signal input to the L34 internal
high capacity solenoid valve in the compressor.
4 − K1−1 closes, energizing the compressor and outdoor fan
motor through the normally closed fan relay contacts on
the defrost board.
D The compressor runs high capacity.
XP16−060−05 only − The 24 volt input to the The
D
compressor runs high capacity yellow and blue
wires of the outdoor fan will provide high speed
operation.