Lennox SL280UHNV - Page 35

Page 35
TABLE 18
Manifold and Pressure Signal wc. Natural
Altitude Unit
Manifold Signal
High
Fire
Low
Fire
High Fire Low Fire
0-4500ft
-060
3.0-3.8 1.3-1.7
0.77-0.85 0.34-0.42
-080 0.78-0.86 0.35-0.43
-100 0.62-0.70 0.30-0.45
4500-
7500ft
-060
2.5-3.3 1.3-1.7 0.60-0.85 0.30-0.45-080
-100
TABLE 19
Manifold and Pressure Signal wc. Propane
Altitude Unit
Manifold Signal
High
Fire
Low
Fire
High Fire Low Fire
0-4500ft
-060
1
3.4-3.8 1.5-1.9
0.77-0.85 0.34-0.42
-080
2
0.78-0.86 0.35-0.43
-100 N/A N/A 0.62-0.70 0.30-0.45
4500-
7500ft
-060
1
2.7-3.2 1.3-1.7 0.60-0.85 0.30-0.45
-080 N/A N/A N/A N/A
-100 N/A N/A N/A N/A
1 Use LP Kit 20P40
2 Use LP Kit 20P41 (0-4500ft only)
Air Orice Replacement -01 through -04 Models
Do not replace the air orice until the problem has been
determined. If the unit has di󰀩culty igniting the orice is
oversized and brings in too much air.
If the unit ignites but with loud resonance the orice is too
small and needs more air. The air orice is located inside
the gray coupling between the clamps. Figure 20 shows
corresponding steps with the steps below.
1 - Turn o󰀨 the electrical power and gas supply to the
furnace.
2 - Remove the air hose tting from the brass tting on
the air inlet screen.
3 - Use a 5/16” nut driver to loosen the clamps on the
gray coupling.
4 - Remove the air inlet screen housing and coupling.
5 - Remove the air orice. Check the “Part” number
stamped on the air orice. See Table 20. If incorrect
replace with proper air orice. Repeat manifold
check. If air orice is correct then it must be
replaced. See Table 20 for replacement.
6 - Reinstall the air orice on the right side of the
coupling and push rmly into place.
7 - Reinstall air inlet housing and coupling making
sure the coupling is fully seated against the air inlet
elbow. Tighten clamps to secure the coupling.
8 - Reconnect the air pressure tubing.
9 - Repeat manifold and signal pressure check. If
unit ignites and manifold and signal pressure are
correct, move on to combustion check. If unit still
does not ignite or ignites with loud resonance go to
Troubleshooting gure 22.
Gray Coupling
2
Inlet Screen
3
4
5
6
7
7
8
Part Number
Air Orifice Replacement -01 to -04 models
FIGURE 20