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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
K132 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 K361 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 deenergizes the safety heater, keeping the burner
operating.
6. A15 energizes accessory relay (K109). When K1091
closes the accessory terminal on the A15 board is ener
gized with 120VAC.
7.
When heat demand is satisfied, W1 of the thermostat
deenergizes W of the ignition control. W deenergizes
K13 in turn deenergizing 1K. When 1K is deener
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 K31 closes B3
starts on the speed set for cooling.
10. A15 energizes accessory relay K109. When K1091
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
deenergizes Y and G. The indoor blower and condensing
unit stops immediately.
