L.B. White AD250(Spark Ignition) - Manual (Page 15)

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1. Shut off the gas supply to the heater.
2. Disconnect the heater from its electrical supply.
3. Open the case fan access panel on the control box
end of the heater.
4. Disconnect the motor leads.
5. Remove the screws securing the motor mounting
plate to the fan housing.
6. Pull the fan and motor assembly from the housing.
7. Loosen the square head set screw(s) on the fan
wheel with a wrench.
8. Pull the fan wheel from the motor shaft. Use a wheel
puller if necessary.
9. Remove the four (4) nuts securing the motor to the
mounting plate.
10. To replace the motor and fan, reverse the above
procedures.
NOTES: a. Fan wheel to motor mount plate spacing
must be adjusted to the clearance
specified in the table below before
tightening the fan wheel to the motor
shaft.
b. Make sure that set screw(s) of the fan are
on the flats of motor shaf t when
tightening.
Model Clearance
AD 250 1/8 - 3/16 In.
FIG. 9
Service Instructions
MOTOR AND FAN WHEEL ASSEMBLY
MOTOR MOUNT PLATE
FAN WHEEL
CLEARANCE
MOTOR
AIR PROVING SWITCH WITH PADDLE
NUTS
SWITCH W/PADDLE
PADDLE
OBLONG HOLE
LEADS
HOUSING SIDE
PANEL
1. Shut off the gas supply to the heater.
2. Disconnect the heater from its electrical supply.
3. Open the case access panel on the control box end of
the heater.
4. 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.
5. Disconnect the leads from the air proving switch.
6. To replace the switch, reverse the above procedure.
The replacement switch will be pre-assembled to its
mounting bracket.
IMPORTANT
Make sure you don’t bend the switch arm when installing
the replacement switch. Bending the switch arm may
create ignition problems later.
FIG. 10