Lennox EL280UHE Series Unit Information page 31

Cleaning the Heat Exchanger and Burners
NOTE - Use papers or protective covering in front of the fur­
nace during cleaning.
1 - Turn off both electrical and gas power supplies to fur­
nace.
2 - Remove flue pipe and top cap (some applications top
cap can remain) from the unit.
3 - Label the wires from gas valve, rollout switches, prima­
ry limit switch and make-up box then disconnect them.
4 - Remove the screws that secure the combustion air in­
ducer/pressure switch assembly to the collector box.
Carefully remove the combustion air inducer to avoid
damaging blower gasket. If gasket is damaged, it must
be replaced to prevent leakage.
5 - Remove the collector box located behind the combus­
tion air inducer. Be careful with the collector box gas­
ket. If the gasket is damaged, it must be replaced to
prevent leakage.
6 - Disconnect gas supply piping. Remove the screw se­
curing the burner box cover and remove cover. Re­
move the four screws securing the burner manifold as­
sembly to the vestibule panel and remove the assem­
bly from the unit.
7 - Remove screws securing burner box and remove
burner box.
8 - NOX units only - Remove screw securing NOX insert.
Remove NOX insert. See figure 24.
9 - Remove screws from both sides, top and bottom of
vestibule panel.
10 -Remove heat exchanger. It may be necessary to
spread cabinet side to allow more room. If so, remove
five screws from the left side or right side of cabinet.
See figure 25.
11 - Backwash using steam. Begin from the burner opening
on each clam. Steam must not exceed 275°F.
12 -To clean burners, run a vacuum cleaner with a soft brush
attachment over the face of burners. Visually inspect in­
side the burners and crossovers for any blockage
caused by foreign matter. Remove any blockage. Figure
23 shows burner detail.
13 -To clean the combustion air inducer visually inspect and
using a wire brush clean where necessary. Use com­
pressed air to clean off debris and any rust.
14 -Reinstall heat exchanger in vestibule. (Replace the
five screws in the cabinet from step 10 if removed).
15 -NOx units only - Replace NOx inserts.
16 -Reinstall collector box and combustion air assembly.
Reinstall all screws to the collector box and combustion
air inducer. Failure to replace all screws may cause
leaks. Inspect gaskets for any damage and replace if
necessary.
17 -Reinstall burner box, manifold assembly and burner box
cover.
Page 31