Lennox SL280UHNV - Page 39

Page 39
TABLE 25
Air Orice Replacement
Capacity Production Di󰀩cult Igniting (Need less combustion air)
Two-Stage Models Air Production Size (Part #) Catalog Number Air Orice Size (Part #) Catalog Number
060 0.880 (28) 23A31 0.860 (05) 25B19
080 1.030 (30) 24G44 1.000 (02) 19X30
100 1.160 (29) 23A32 1.140 (24) 22J97
Gray Coupling
Air Orice
Air Intake Coupling
Loosen Clamps
Air Orice Location -05 and later models
Aluminum Elbow
Pressure Switch
With Bracket
FIGURE 23
Air Orice Replacement -05 Models
Do not replace the air orice until the problem has been
determined. If the unit has di󰀩culty igniting the air orice
is oversized and brings in too much combustion air. If the
unit ignites but with loud resonance, go to Troubleshoot-
ing. The air orice is located inside the gray coupling be-
tween the clamps. See gure 23 for air orice location.
1 - Turn o󰀨 the electrical power and gas supply to the
furnace.
2 - Remove the air pressure tubing from the tting on
the aluminum elbow and air intake coupling.
3 - Use a 5/16” nut driver to loosen the clamp on the
right side of the gray coupling.
4 - Remove the four screws on the aluminum elbow,
make note of the pressure switch bracket location.
It may be necessary to disconnect the gas pipe to
the gas valve before removing the screws.
5 - Remove the air orice. Check the “Part” number
stamped on the air orice. See table 25. If incorrect
replace with proper air orice. Repeat manifold
check. If air orice is correct then it must be
replaced. See table 25 for replacement.
6 - Reinstall the air orice on the right side of the
coupling and push rmly into place.
7 - . Reinstall aluminum elbow with the four screws
removed from step 4. Make sure the gray coupling
is fully seated again the aluminum elbow and the
pressure switch bracket is in the correct location.
The bracket should be under the screw head
and not under the ange on the aluminum elbow.
Tighten clamp to secure the gray coupling. Reinstall
the gas pipe to gas valve.
8 - Reconnect the air pressure tubing.
9 - Repeat manifold and system operating pressure
check. If unit ignites and manifold and system
operating pressures are correct, move on to
combustion check. If unit still does not ignite or
ignites with loud resonance go to Troubleshooting.