Lennox O23 User Manual

Page 28
VIII−WIRING DIAGRAMS AND SEQUENCE OF OPERATIONS
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O23 / OHR23 / OF23−1 through −4 UNIT OPERATION SEQUENCE:
1. When disconnect is closed, 120V is routed to the blower
control board BCC2 (A15). The BCC2 feeds line voltage
to transformer (T1).
2. T1 supplies 24VAC to the burner control (A3). In turn, A3
supplies 24VAC to A15, which supplies the indoor ther
mostat (not shown) with 24VAC.
3. When there is a call for heat, W1 of the thermostat ener
gizes W of the A15 board with 24VAC.
4. A15 energizes combustion air blower relay (K13). When
K132 closes, assuming primary limit (S10) and [secon
dary limit (S21) in OHR units only] are closed, 24VAC is
routed to 1K, which closes 1K1 and 1K2. When 1K2
closes combustion air blower / pump (B6) is energized.
Simultaneously 24VAC is routed through the blower relay
(K36). When K361 closes blower motor (B6) is ener
gized on heating speed.
5. When 1K2 closes the electronic ignitor is energized
causing a 14,000VAC spark, igniting the burner. When
1K1 closes the solid state switch and cad cell are ener
gized. When the cad cell senses light the solid state
switch deenergizes the safety heater, keeping the burner
operating.
6. A15 energizes accessory relay (K109). When K1091
closes the accessory terminal on the A15 board is ener
gized with 120VAC.
7. When heat demand is satisfied, W1 of the thermostat
deenergizes W of the ignition control. W deenergizes
K13 in turn deenergizing 1K. When 1K is deener
gized B6 and A73 stop immediately. The indoor blower
runs for a designated fan off" period (90−330 seconds)
as set by jumper on BCC2 control.
8. When there is a call for cooling, Y1 of the thermostat ener
gizes Y and G of the A15 board with 24VAC.
9. A15 energizes blower relay K3. When K31 closes B3
starts on the speed set for cooling.
10. A15 energizes accessory relay K109. When K1091
closes the accessory terminal on the A15 board is ener
gized with 120VAC.
11. Provided that condensing unit is connected to Y ter
minal, cooling will start.
12. When cooling demand is satisfied, Y1 of the thermostat
deenergizes Y and G. The indoor blower and condensing
unit stops immediately.

Lennox O23 Specifications

General

Brand	Lennox
Model	O23
Category	Furnace
Language	English