Lennox ML193DFE Series Unit Information page 46

Condensate Hose Screen
FIGURE 57
Cleaning Heat Exchanger
If cleaning the heat exchanger becomes necessary, follow
the below procedures and refer to figure 1 when disas-
sembling unit. Use papers or protective covering in front of
furnace while removing heat exchanger assembly.
1 - Turn off electrical and gas supplies to the furnace.
2 - Remove the furnace access panels.
3 - Disconnect the 2 wires from the gas valve.
4 - Remove gas supply line connected to gas valve.
remove as valve/manifold assembly.
5 - Remove sensor wire from sensor. Disconnect 2-pin
plug from the ignitor.
6 - Disconnect wires from flame roll-out switches.
7 - Loosen clamps
condensate drain tubing from flue collar. and
remove the vent elbow.
8 - Remove four burner box screws at the vestibule
panel and remove burner box. Set burner box
assembly aside.
NOTE - If necessary, clean burners at this time.
Follow procedures outlined in Burner Cleaning
section.
9 - Mark and disconnect all combustion air pressure
tubing from cold end header collector box.
10 - Mark and remove wires from pressure switches.
Remove pressure switches. Keep tubing attached
to pressure switches.
11 - Disconnect the plug from the combustion air inducer.
Remove two screws which secure combustion air
inducer to collector box. Remove combustion air
inducer assembly. Remove ground wire from vest
panel.
12 - Remove electrical junction box from the side of the
furnace.
13 - Mark and disconnect any remaining wiring to
heating compartment components. Disengage
strain relief bushing and pull wiring and bushing
through the hole in the blower deck.
14 - Remove the primary limit from the vestibule panel.
15 - Remove two screws from the front cabinet flange
atthe blower deck. Spread cabinet sides slightly to
allow clearance for removal of heat exchanger.
Hose
at vent elbow. Disconnect
16 - Remove screws along vestibule sides and bottom
which secure vestibule panel and heat exchanger
assembly to cabinet. Remove two screws from
blower rail which secure bottom heat exchanger
flange. Remove heat exchanger from furnace
cabinet.
17 - Back wash heat exchanger with soapy water
solution or steam. If steam is used it must be below
275°F (135°C) .
18 - Thoroughly rinse and drain the heat exchanger.
Soap solutions can be corrosive. Take care to rinse
entire assembly.
19 - Reinstall heat exchanger into cabinet making sure
that the clamshells of the heat exchanger assembly
are resting on the support located at the rear of the
cabinet. Remove the indoor blower to view this area
through the blower opening.
20 - Re-secure the supporting screws along the
vestibule sides and bottom to the cabinet. Reinstall
blower and mounting screws.
21 - Reinstall cabinet screws on front flange at blower
deck.
22 - Reinstall the primary limit on the vestibule panel.
23 - Route heating component wiring through hole in
blower deck and reinsert strain relief bushing.
24 - Reinstall electrical junction box.
25 - Reinstall the combustion air inducer. Reconnect the
combustion air inducer to the wire harness.
26 - Reinstall pressure switches and reconnect pressure
switch wiring.
27 - Carefully connect combustion air pressure switch
hosing from pressure switches to proper stubs on
cold end header collector box.
28 - Reinstall condensate trap.
29 - Reconnect exhaust piping and exhaust drain tubing.
30 - Reinstall burner box assembly in vestibule area.
31 - Reconnect flame roll-out switch wires.
32 - Reconnect sensor wire and reconnect 2-pin plug
from ignitor.
33 - Secure burner box assembly to vestibule panel
using four existing screws. Make sure burners line
up in center of burner ports.
34 - Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
35 - Reconnect 2 wires to gas valve.
36 - Replace the blower compartment access panel.
37 - Refer to instruction on verifying gas and electrical
connections when re-establishing supplies.
38 - Follow lighting instructions to light and operate
furnace for 5 minutes to ensure that heat exchanger
is clean and dry and that furnace is operating
properly.
39 - Replace heating compartment access panel.
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