ÐCleaning Heat Exchanger Cell, A91252

9.Mark blower wheel, motor, and motor support in relation to blower housing before disassembly to ensure proper reassem- bly.

10.Loosen setscrew holding blower wheel on motor shaft.

11.Remove bolts holding motor mount to blower housing and slide motor and mount out of housing. Disconnect ground wire attached to blower housing before removing motor.

12.Lubricate motor (when oil ports are provided).

a.Remove dust caps or plugs from oil ports located at each end of motor.

b.Use a good grade of SAE 20 nondetergent motor oil and put 1 teaspoon, 5 cc, 3/16 oz, or 16 to 25 drops in each oil port. Do not over-oil.

c.Allow time for total quantity of oil to be absorbed by each bearing.

d.Wipe excess oil from motor housing.

e.Replace dust caps or plugs on oil ports.

13.Remove blower wheel from housing.

a.Mark cutoff location to ensure proper reassembly.

b.Remove screws holding cutoff plate and remove cutoff plate from housing.

c.Lift blower wheel from housing through opening.

14.Clean blower wheel and motor using a vacuum cleaner with soft brush attachment. Do not remove or disturb balance weights (clips) on blower wheel blades. The blower wheel should not be dropped or bent as balance will be affected.

15.Reinstall blower wheel by reversing steps 13 a. through c. Be sure wheel is positioned for proper rotation.

16.Reassemble motor and blower by reversing steps 5 through 11. If motor has ground wire, be sure it is connected as before.

Be sure the motor is properly positioned in the blower housing. The motor oil ports must be at a minimum of 45° above the horizontal centerline of the motor after the blower assembly has been reinstalled in the furnace.

17.Reinstall blower assembly in furnace. Connect electrical leads to blower speed selector. Connections are polarized for assembly. DO NOT FORCE.

18.Reinstall control box.

19.Reconnect wires to auxiliary limit switch on blower housing (downflow furnace only).

20.Reinstall vent pipe and enclosure (downflow furnaces only).

21.Turn on electrical power and check for proper rotation and speed changes between heating and cooling.

22.Replace blower access door and secure with 2 screws (down- flow furnace only).

CLEANING HEAT EXCHANGER

The following steps should be performed by a qualified service technician:

NOTE: Deposits of soot and carbon indicate the existence of a problem which needs to be corrected. Take action to correct the problem.

If it becomes necessary to clean the heat exchanger because of carbon deposits, soot, etc., proceed as follows:

1.Turn off gas and power to furnace.

2.Remove 2 screws from blower access door (downflow furnace only). Remove control and blower access doors.

3.Remove vent pipe enclosure (downflow furnace only) and disconnect vent pipe from relief box.

4.Remove 2 screws that secure relief box. (See Fig. 4 or 5.)

5.Disconnect wires to the following components:

a.Draft safeguard switch

b.Inducer motor

c.Pressure switch

d.Limit overtemperature switch

e.Gas valve

f.Edge connector leading to control box

6.Remove 8 screws that secure flue collector box to center panel. Be careful not to damage sealant.

7.Remove complete inducer assembly from furnace, exposing flue openings.

8.Clean cells as follows using field-provided small wire brush, steel spring cable, reversible electric drill, and vacuum cleaner.

a.Assemble wire brush and steel spring cable.

(1.) Use 48 in. of 1/4-in. diameter high-grade steel spring cable (commonly known as drain clean-out or Roto- Rooter cable).

(2.) Use 1/4-in. diameter wire brush (commonly known as 25-caliber rifle cleaning brush).

NOTE: The items needed in steps (1.) and (2.) can usually be purchased at local hardware stores.

(3.) Insert twisted wire end of brush into end of steel spring cable, and crimp tight with crimping tool or strike with ball-peen hammer. TIGHTNESS is very important.

(4.) Remove metal screw fitting from wire brush to allow insertion into cable.

b.Clean each heat exchanger cell.

(1.) Attach variable-speed, reversible drill to end of steel spring cable (end opposite brush).

(2.) Insert brush end of cable into upper opening of cell and slowly rotate with drill. DO NOT force cable. Gradually insert at least 36 in. of cable into 2 upper passes of cell. (See Fig. 6.)

A91252

Fig. 6ÐCleaning Heat Exchanger Cell

(3.) Work cable in and out of cell 3 or 4 times to obtain sufficient cleaning. DO NOT pull cable with great force. Reverse drill and gradually work cable out.

(4.) Remove burner assembly and cell inlet plates.

(5.) Replace screws in center panel and cells before cleaning.