Procedure 4 - Cleaning Heat Exchangers, Drainage System

Procedure 4 — Cleaning Heat Exchangers

The following items should be performed by a qualified service technician.

A. Primary Heat Exchangers

If heat exchangers get an accumulation of light dirt or dust on the inside, they may be cleaned by the following procedure:

NOTE: If heat exchangers get a heavy accumulation of soot and carbon, both the primary and secondary heat exchangers 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, improper vent termination, incorrect size or damaged manifold orifice(s), improper gas, or a restricted heat exchanger (primary or secondary). Action must be taken to correct the problem.

1.Turn off gas and electrical supplies to furnace.

2.Remove main furnace door.

!CAUTION

ELECTRICAL SHOCK, UNIT DAMAGE HAZARD

Failure to follow this caution may result in personal injury or furnace component damage.

Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and dangerous operation.

3.Disconnect wires or connectors to flame rollout switch, gas valve, igniter, and flame sensor.

4.Using backup wrench, disconnect gas supply pipe from gas valve.

5.Remove screws attaching burner box to cell panel. (See Fig. 4.)

NOTE: Burner box, manifold, gas valve, and burner assembly should be removed as 1 assembly.

6.Clean heat exchanger openings with a vacuum and a soft brush. (See Fig. 5.)

NOTE: After cleaning, inspect heat exchangers to ensure they are free of all foreign objects that may restrict flow of combustion products.

7. Reverse items 4 and 5 for reassembly.

!CAUTION

UNIT MAY NOT OPERATE

Failure to follow this caution may result in improper unit operation.

The ground wire from the gas valve MUST be attached to the burner box attachment screw or furnace lockout may occur.

8.Refer to furnace wiring diagram and connect wires to flame rollout switch, gas valve, igniter, and flame sensor.

9.Reconnect pressure switch tubes to gas valve and intake housing. Refer to tube routing label on main furnace door for proper tube location. Be sure tubes are not kinked. (See Fig. 6 - 14.)

10.Turn on gas and electrical supplies to furnace.

11.Check furnace operation through 2 complete heat operating cycles. Burner flames should be clear blue, almost transparent. (See Fig. 15.)

!WARNING

FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings could result in personal
injury, death, or property damage.
injury, death, or property damage.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically for the		359AAV
detection of leaks to check all connections.		359AAV
detection of leaks to check all connections.

12.	Check for gas leaks.
13.	Replace main furnace door.

B. Secondary Heat Exchangers

NOTE: The condensing side (inside) of secondary heat exchangers CANNOT be serviced or inspected. A small number of bottom outlet openings can be inspected by removing inducer assembly. See Flushing Collector Box and Drainage System section for details on removing inducer assembly.