ÐCleaning Heat Exchangers, Primary Heat Exchangers

Never use matches, candles, flame, or other sources of ignition to check for gas leakage. Use a soap-and-water solution. Failure to follow this warning could result in a fire, personal injury, or death.

19. Replace main furnace door.

Step 4ÐCleaning Heat Exchangers

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

PRIMARY HEAT EXCHANGERS

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

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

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

4.Disconnect combustion-air intake pipe from intake housing.

5.Remove the pressure switch tube from intake housing.

6.Remove screws attaching intake housing to burner box, and rotate intake housing away from burner box for removal.

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

8.Disconnect pressure tubing from gas valve.

9.Remove 2 screws attaching top filler panel and rotate upwards to gain access to screws attaching burner box to cell panel.

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

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

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

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

12. Reverse items 4 through 10 for reassembly.

The ground wire from the gas valve MUST be attached to the burner box attachment screw. Failure to attach this ground wire to an adequate casing ground will cause the furnace control to lock out.

NOTE: Be sure burner box gasket is installed between burner box and cell panel. If gasket is damaged, replace it.

PRIMARY HX

INLET OPENINGS

A93080

Fig. 6ÐCleaning Inlet Openings of Primary Heat

Exchangers

NOTE: Inspect combustion-air intake housing. If foamed gasket was removed, check for any damage. If gasket is damaged in any way, it must be repaired. To repair, remove damaged gasket section, apply sealant releasing agent such as PAM cooking spray or equivalent (must not contain corn or canola oil, aromatic or halogenated hydrocarbons) to burner box and apply a small bead of G.E. RTV 162, G.E. RTV 6702, or Dow-Corning RTV 738 sealant to edge of combustion-air intake housing. (See Fig. 7.)

RTV

PAM

A93087

Fig. 7ÐCombustion-Air Intake Housing Gasket

Repair

13.Refer to furnace wiring diagram and reconnect wires to rollout switch, gas valve, ignitor, and flame sensor.

14.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. 8.)

15.Turn on gas and electrical supplies to furnace.

16.Check furnace operation through 2 complete heat operating cycles. Look through sight glass in burner enclosure to check burners. Burner flames should be clear blue, almost transpar- ent. (See Fig. 9.)

17.Check for gas leaks.