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O23 / OHR23 / OF23−5 UNIT OPERATION SEQUENCE
:
1. When disconnect is closed, 120V is routed to the blower
control board (A15). The blower control board feeds line
voltage to transformer (T1).
2. When there is a call for heat, W1 of the thermostat ener
gizes W of the A15 board with 24VAC.
3. A15 energizes combustion air inducer B6 assuming pri
mary limit (S10) and [secondary limit (S21) in OHR units
only] are closed.
4. Burner control A3 energizes the electronic ignitor caus
ing a 20,000VAC spark . Burner motor (B6) and pump
valve (L35) are delayed for a 15 second pre−purge. The
pre−purge is followed by a 15 second trial for ignition.
5. After the pre−purge and trial for ignition (30 seconds)
voltage passes through contactor K1 the energizing the
indoor blower B3 on heating speed.
6.
When heat demand is satisfied, W1 of the thermostat
deenergizes W of the ignition control. Combustion air
inducer B6 is de−energized. The indoor blower runs for
a designated fan off" period (60−150 seconds) as set
delay switch on blower control.
7. When there is a call for cooling, Y1 of the thermostat ener
gizes Y and G of the A15 board with 24VAC.
8. A15 energizes relay K2. When K2 contacts close, the in
door blower B3 energizes on cooling speed.
9.
When cooling demand is satisfied, Y1 of the thermostat
deenergizes Y and G. The indoor blower and condensing
unit stops immediately.
10. When there is a call for continuous fan the indoor blower
(B3) is energized on cool speed. If blower control board
is wired for continuous fan, the indoor blower will energize
on low speed and remain energized after thermostat de
mand is satisfied.
