Cleaning Heat Exchangers, Unit MAY not Operate

21.Check for gas leaks.

22.Replace main furnace door.

Step 4 — Cleaning 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 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 orifices(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

UNIT DAMAGE HAZARD

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

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

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

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 fur- nace gas control valve.

8.Disconnect pressure tubing from gas valve.

PRIMARY HX

INLET OPENINGS

A96305

Fig. 8 - Cleaning Inlet Openings of Primary

Heat Exchangers

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

10.Remove screws attaching burner box to cell panel. (See Fig. 6).

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

11.Clean heat exchanger openings with a vacuum and a soft brush. (See Fig. 8.)

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

12.Reverse items 4 through 10 for reassembly.

!CAUTION

UNIT MAY NOT OPERATE

Failure to attach this ground wire to an adequate casing ground may cause the furnace control to lock out.

The ground wire from the gas valve MUST be attached to the burner box attachment screw.

NOTE: Be sure burner box gasket is installed between burner box and cell panel. (See Fig. 6.) If gasket is damaged, replace it.

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 nor canola oil, halogenated hydrocarbons nor aromatic content, to prevent inadequate seal from occurring) 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. 9.)

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

14.Reconnect pressure switch tubes to gas valve and intake housing. Refer to tube routing label on main furnace door or Fig. 10 for proper tube location. Be sure tubes are not kinked.

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 transparent. (See Fig. 11.)

!WARNING

FIRE OR EXPLOSION HAZARD

Failure to follow this safety warning could result in personal injury, death, or property damage.

Never test for gas leaks with an open flame. Use a commercially available soap solution made specifically for the detection of leaks to check all connections.

17.Check for gas leaks.

18.Replace main furnace door.

SECONDARY HEAT EXCHANGERS

NOTE: The condensing side (inside) of the secondary heat exchangers CANNOT be serviced or inspected. A small number of bottom outlet openings can be inspected by removing the

58MEC