L.B. White AW250(building controller) - Manual (Page 16)

16
AIR PROVING SWITCH WITH PADDLE
NUTS
SWITCH W/PADDLE
PADDLE
OBLONG HOLE
LEADS
HOUSING SIDE
PANEL
1. Open the case access panel on the control box end of
the heater.
2. Remove the two (2) sheet metal screws holding the
switch with bracket to blower housing. Remove the
assembly by turning the switch assembly 90°so the
paddle on the switch arm can be pulled through the
oblong hole on side of fan housing.
3. Disconnect the leads from the air proving switch.
4. To replace the switch, reverse the above procedure.
The replacement switch will be pre-assembled to its
mounting bracket.
FIG. 11
1. See Fig. 12 for dissassembly.
2. Position the replacement igniter so its lip and
mounting slot and screw hole of igniter bracket.
3. Reassemble remaining parts. Tighten the mounting
screw snugly. ( Do not overtighten).
Testing
-- Perform an ohm check across the igniter leads of a
cold igniter. Ohm readings will vary somewhat, but
generally will be in the 40-70 ohm range. A reading
showing overload or infinite resistance indicates a
defective igniter.
IGNITER
1. Remove the sensor from its mounting bracket. See
Figs. 12 and 13. Clean the sensor rod with steel wool
or emery cloth. Rub briskly to remove build up of dust,
dirt and aluminum oxide. 2. Check the flame sensor’s insulator base for cracks. If
cracks are found, replace the sensor.
3. Position the flame sensor as shown in Fig. 13.
FLAME SENSOR
IGNITER
SHIELD
SCREW
WASHER
MALE CONNECTOR
FEMALE CONNECTOR
SCREW
BRACKET
BURNER
SENSOR
BURNER
FLAME
BURNER
CASTING
FLAME SENSOR
3/8 TO 1/2 IN.
1/2 to 3/4 in. FIG. 12 FIG. 13