39
8. Run the furnace through two complete heating cycles to
check for proper operation
9. Install control door when complete.
CLEANING HEAT EXCHANGER
The following steps should be performed by a qualified
service agency:
NOTE
: If the heat exchangers get a heavy accumulation of soot
and carbon, they should be replaced rather than trying to clean
them thoroughly. A heavy build--up of soot and carbon indicates
that a problem exists which needs to be corrected, such as
improper adjustment of gas valve outlet pressure, insufficient or
poor quality combustion air, incorrect size or damaged 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 exchangers because of
dust or corrosion, proceed as follows:
1. Turn OFF gas and electrical power to furnace.
2. Remove outer access door.
3. Disconnect vent connector from furnace vent elbow.
4. Disconnect wires to the following components. Mark
wires to aid in reconnection of (be careful when discon-
necting wires from switches because damage may occur):
a. Inducer motor
b. Transducer
c. Limit over--temperature switch
d. Gas valve
e. Hot surface ignitor
f. Flame--sensing electrode
g. Burner thermal switch
h. DSS Draft Safeguard
5. Remove screws that fasten the inducer cover assembly to
the cell panel. Be careful not to damage the collector box.
Inducer assembly and elbow need not be removed from
collector box.
6. Disconnect gas supply line from gas valve.
7. Remove screws that attach the burner assembly to the cell
panel. The gas valve and burners tube need not be re-
moved from burner box.
NOTE
: Be very careful when removing burner assembly to
avoid breaking ignitor.
8. Remove insulation assembly from burner tube inlets.
NOTE
: Proper use of Personal Protective Equipment (PPE)
must be followed, including safety glasses, gloves, and dust mask
when removing and reinstalling the heat exchanger insulation
assembly.
9. Using field--provided large caliber rifle cleaning brush,
36--in. (914 mm) long steel spring cable, a variable speed,
reversible electric drill, and vacuum cleaner, clean cells as
follows:
NOTE
:
The materials needed in item 9. can usually be
purchased at local hardware stores.
a. Remove metal screw fitting from wire brush to allow in-
sertion into cable.
b. Insert the twisted wire end of brush into end of spring
cable, and crimp tight with crimping tool or crimp by
striking with ball--peen hammer. TIGHTNESS IS VERY
IMPORTANT.
A180230
Fig. 43 -- Ignitor Position
(1.) Attach variable--speed, reversible drill to the end of
spring cable (end opposite brush).
(2.) Insert brush end of cable into the outlet opening of
cell and slowly rotate with drill. DO NOT force
cable. Gradually insert cable into upper pass of cell.
(See Fig. 44)
(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 burner inlet opening of
cell, and proceed to clean two lower passes of cell
in same manner as upper pass.
(5.) Repeat foregoing procedures until each cell in
furnace has been cleaned.
(6.) Using vacuum cleaner, remove residue from each
cell.
(7.) Using vacuum cleaner with soft brush attachment,
clean burner assembly.
(8.) Clean flame sensor with fine steel wool.
(9.) Reinstall the insulation assembly.
NOTE
: If insulation assembly is damaged, do not attempt to
repair, must be replaced with insulation kit.
NOTE
: Proper use of Personal Protective Equipment (PPE)
must be followed, including safety glasses, gloves, and dust mask
when removing and reinstalling the heat exchanger insulation
assembly.
(10.) Reinstall burner assembly.
10. Remove old sealant from cell panel and collector box
flange.
11. Spray releasing agent on the heat exchanger cell panel
where inducer cover assembly contacts cell panel.
NOTE
: A releasing agent such as cooking spray or equivalent
(must not contain corn or canola oil, aromatic or halogenated
hydrocarbons or inadequate seal may occur) and RTV sealant
(G.E. 162, 6702, or Dow--Corning 738) are needed before
starting installation.
NOTE
: DO NOT substitute any other type of RTV sealant.
12. Apply new sealant to flange of collector box and attach to
cell panel using existing screws, making sure all screws
are secure.
13. Reconnect wires to the following components. (Use
connection diagram on wiring label, if wires were not
marked for reconnection locations.):
a. Inducer motor
b. Transducer
