Lennox International Inc. o23v - Manual (Page 10)

Page 10
I−Cad Cell (R26)
Together the cad cell and the burner control prove flame.
The cad cell senses the presence of burner light (less re-
sistance) to close a circuit to the burner control.
IMPORTANT−Burner should not be installed so it is ex-
posed to direct sunlight or electric bulb light. If the cell
is exposed to light on start up, the burner will not oper-
ate.
Resistance for the cad cell can be checked while the burn-
er is firing and after ignition is off. Press (1/2 second or
less) and release the reset button. The LED will flash 1 to 4
times depending on the cad cell resistance. The cad cell
resistance should read less than 1600 Ohms. See table 7.
TABLE 7
LED FLASHES RESISTANCE
1 0 − 400Ohms
2 400 − 800 Ohms
3 800 − 1600 Ohms
4
 1600 Ohms
J−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 with 120V primary and 20,000V secon-
dary windings. The center of the secondary winding is
grounded. Each secondary terminal is 7000V to ground
and the total voltage 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.
Testing the Ignitor
WARNING
SHOCK HAZARD
Do not touch ignitor or any metal touching ignitor
when ignitor is energized. Can result in serious per-
sonal injury.
If the ignitor fails it will not produce a spark. Looking and
listening for the arc is a simple way to check. The most sure
way is to perform the screwdriver check. By placing the
blade of an insulated screwdriver across the ignitor termi-
nal leads will test for an arc. First, remove power from the
burner and disconnect the oil supply from nozzle. The cad
cell will not let the control energize the ignitor if the cad cell
senses light. Therefore remove one lead of the cad cell
from the burner control, or remove the cad cell all together
(do not forget to put back when test is complete). Place the
screwdriver blade across the terminals and slowly raise
one end of the blade off the terminal while the other re-
mains in contact with the other terminal. There should be
an arc from terminal to the blade up to 3/4" away. If not re-
place the ignitor. If an arc is present then place one end of
the screwdriver on one terminal and the other end with the
grounded baseplate. Raise the blade from the baseplate
and draw an arc. Repeat with the other terminal. If the arc
from the baseplate to one terminal is weaker than the arc
from the baseplate to the other terminal, replace the ignitor.
K−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.
L−Flame Retention Heads
The stainless steel flame retention head (see figure 4) is
used to swirl (cone) the fog-like oil and air mixture as it
enters the combustion chamber. Three different heads
are used in the O23V. The firing rate dictates which
head is used. See table 6. 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