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Service instructions, Motor and fan wheel assembly, Air proving switch with paddle – L.B. White AD250(Spark Ignition) User Manual

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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