Lennox CBX25UHV Series Installation And Service Procedure page 31

VIII-SEQUENCE OF OPERATIONS
Heat Pump Heating — On a call for heat pump heating, the
room thermostat sends a 24VAC signal from terminal Y1 to
pin 6 on the blower motor (a field-provided jumper connects
terminals Y1 and Y2 on the air handler). The green wire
from the air handler terminal G carries a 24VAC signal to
pin 3 of the circuit board.
The blower motor cycles on at the selected heat pump
heating speed. The Y1 terminal on the room thermostat is
connected to the Y terminal in the outdoor unit. The air
handler C (Common) terminal is connected to terminal C in
the outdoor units. The contactor closes to bring on the
compressor and outdoor fan motor.
Cooling — On a call for cooling, the room thermostat sends
a 24 volt signal from terminal Y1 to pin 6 on the blower motor
(a field-provided jumper connects terminals Y1 and Y2 on
the air handler). A field-installed jumper between air
handler terminals R and O supplies a 24VAC signal from
the air handler O terminal to blower motor pin 9. The green
wire from air handler terminal G carries a 24VAC signal to
pin 3 of the circuit board.
The blower motor cycles on at the selected cooling blower
speed. The Y1 terminal on the room thermostat is
connected to the Y terminal on the outdoor unit. The air
handler C (Common) terminal is connected to terminal C in
the outdoor unit. The contactor in the outdoor closes to
bring on the compressor and outdoor fan motor.
Heating -- First-Stage Electric Heat with Conventional
Thermostat — On a call for heating, the room thermostat
sends a 24VAC signal to the air handler terminal W1.
The wire from W1 to terminal 5 on the 5-pin plug energizes
the coil in sequencer relay SEQ1.
If limit switches LS1 and LS2 are closed, sequencer relay
(SEQ1) normally open contacts 4 and 5 and 1 and 3 close
after a time delay to energize heating elements HE1 and
HE2.
The wire from SEQ1 terminal 5 carries 240VAC power to
pin 3 on the 6-pin plug to energize the blower relay coil.
The blower relay contacts close immediately to provide
24VAC power to terminal 2 on the circuit board.
A heating blower demand is sent from circuit board terminal
7 to pin 2 (W/W1) on the 16-pin plug on the blower motor.
The indoor blower is energized on the heating speed.
Heating -- Second-Stage
Conventional Thermostat — On a call for second-stage
heating, the room thermostat sends a 24VAC signal to the
air handler terminal W2.
The wire from W2 to terminal 6 on the 6-pin plug energizes
the coil in the sequencer relay SEQ2.
If limit switches LS3 and LS4 are closed, sequencer relay
SEQ2 normally open contacts 4 and 5 and 1 and 3 close
after a time delay to energize heating elements HE3 and
HE4.
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Electric Heat with