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6-Electronic Ignitor (A73)
The electronic ignitor provides the needed hot spark at the
electrodes to ignite the fuel mixture. The ignitor is a solid state
transformer which has 115V primary and 14,000V secondary
windings. The center of the secondary winding is grounded.
Each secondary terminal is 7000V to ground and the total volt
age between the electrodes is 14,000V.
NOTE-The leads for the solid state transformer are re
placeable and are available in a kit form.
NOTE-When testing the solid state transformer, do not
use a transformer tester designed for iron magnet trans
formers. Damage to the tester may result.
7-Gun Assembly
The gun assembly receives oil from the oil pump and feeds
it to the nozzle. The nozzle converts liquid oil into a fog-like
mist that is discharged through the flame retention head
into the combustion chamber.
8-Flame Retention Heads
The stainless steel flame retention head (see figure 4) is
used to swirl (cone) the foglike oil and air mixture as it
enters the combustion chamber. Three different heads
are used in the O24/OF24. The firing rate dictates which
head is used. See table 1. The greater the FB number the
larger the slots on the head. When combustion takes
place, the flame will be cylindrical compact shaped as a
result.
FLAME RETENTION HEAD
FB3 SHOWN
FIGURE 4
B-Primary Fan/Limit Control (S10)
The primary limit on all O24and OF24 units, is located on
the vestibule panel (see figures 1 and 2 for location and fig
ure 5 for type). When excess heat is sensed in the heat ex
changer, the limit will open. If the limit is tripped, the blower
control deenergizes the thermostat, in turn shutting
down the unit. The limit automatically resets when unit tem
p
erature
returns to normal. See table 2 for limit set-points. The
fan control is factory set and is temperature acuated to con
trol blower operation. The fan control is set at 125
F (52
C )
on /100
F (38
C) off.
CAUTION
This furnace must not operate with a FAN ON
temperature greater than 130 degrees.
TABLE 2
PRIMARY LIMIT CONTROL (S10)
UNIT
ACTUATES
ON TEMP. RISE
ACTUATES
ON TEMP. FALL
O24-70
210
F (99
C)
180
F (82
C)
O24-105/120
220
F (104
C)
190
F (88
C)
O24-140/154
210
F (99
C)
180
F (82
C)
OF24-105/120
OF24-105/120R
240
F (116
C)
210
F (99
C)
OF24-140/154
OF24-140/154R
210
F (99
C)
180
F (82
C)
FIGURE 5
LIMIT CONTROL (S10)
S10
