Bryant 393AAV instruction manual III. Cleaning Heat Exchanger, Ð4Ð

WARNING: Blower access door switch opens 115-v power to control center. No component operation can occur. Caution must be taken when manually closing this switch for service purposes. Failure to follow this warn- ing could result in electrical shock, personal injury, or death.

NOTE: If thermostat terminals are jumpered before blower ac- cess door switch is closed, blower will run for 90 sec before beginning a heating or cooling cycle.

14.If furnace is operating properly, REMOVE TAPE TO RELEASE BLOWER ACCESS DOOR SWITCH, replace blower access door.

III.CLEANING HEAT EXCHANGER

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

13 32"

BURNER

11 32"

CELL

PANEL

HOT SURFACE IGNITOR ASSEMBLY

NOTE: If the heat exchangers get a heavy accumulation of soot and carbon, they should be replaced rather than trying to clean them thoroughly due to their intricate design. A build-up of soot and carbon indicates that a problem exists which needs to be corrected, such as improper adjustment of manifold pressure, insufficient or poor quality combustion air, incorrect size, or damaged manifold orifice(s), improper gas, or a restricted heat exchanger. Action must be taken to correct the problem.

If it becomes necessary to clean the heat exchanger because of dust or corrosion proceed as follows:

1.Turn gas and electrical power to furnace to OFF.

2.Remove control access door.

3.Disconnect vent connector from furnace flue collar.

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

5.Disconnect wires to the following components. Mark wires to aid in reconnection of:

a.Blocked vent safeguard switch.

b.Inducer motor.

c.Pressure switch.

d.Limit overtemperature switch(es).

e.Gas valve.

f.Hot surface ignitor.

g.Flame-sensing electrode

h.Flame rollout switch(es), if applicable.

6.Remove complete inducer assembly and relief box from furnace.

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

8.Remove burner assembly and cell inlet plates. IMPORTANT: Replace screws in center panel before cleaning.

NOTE: Be very careful when removing burner assembly to avoid breaking ignitor. See Fig. 3 for correct ignitor location.

9.Using field-provided small wire brush, steel spring cable, reversible electric drill, and vacuum cleaner, clean cells as follows:

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-Rootertcable).

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

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

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C IGNITOR

L

7 8"

C BURNER

L

IGNITOR

ASSEMBLY

A93347

Fig. 3ÐPosition of Ignitor to Burner

(3.) Insert twisted wire end of brush into end of 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 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. 4.)

A91252

Fig. 4±Cleaning 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.) Insert brush end of cable in lower opening of cell, and proceed to clean 2 lower passes of cell in same manner as 2 upper passes.