Proper Combustion; High Altitude - Lennox MERIT Series Installation Instructions Manual

Proper Combustion

Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. Take combustion sample beyond the flue outlet
and compare to the table below. The maximum carbon
monoxide reading should not exceed 100 ppm.
TABLE 16
CO % For Nat
ML296
2
Model Low Fire
045 5.6 - 6.6
070 5.5 - 6.5
090 5.9 - 6.9
0 - 4500 ft
Unit Gas
Low
Fire
Natural 1.7
All
LP/
Sizes
4.5
Propane
NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction
for the conversion procedure.
Unit
045
070
090
* Conversion requires installation of a gas valve manifold spring which is provided with the gas conversion kit. Pressure switch is factory
set. No adjustment necessary. All models use the factory-installed pressure switch from 0-4500 feet (0-1370 m).
CO % For L.P
2
High Fire Low Fire High Fire
7.8 - 8.8 6.6 - 7.6 9.1 - 10.1
7.3 - 8.3 6.5 - 7.5 8.6 - 9.6
7.8 - 8.8 6.9 - 7.9 9.1 - 10.1
Manifold and Supply Line Pressure 0-10,000ft.
4501 - 5500 ft.
High Low High
Fire Fire Fire
3.5 1.6 3.3
10.0 4.2 9.4
Conversion Kit and Pressure Switch Requirements at Varying Altitudes

High Altitude

Natural to
Natural Burner
LP/Propane
Orifice Kit
0 - 7500 ft 7501 - 10,000 ft
*11K51 73W37
High Altitude Information
NOTE - In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local
authorities.
Units may be installed at altitudes up to 10,000 ft. above
sea level without manifold adjustment. Units installed at al-
titude of 4501 - 10,000 feet (1373 to 3048m) may require a
pressure switch change which can be ordered separately.
TABLE 18 lists conversion kit and pressure switch require-
ments at varying altitudes. The combustion air pressure
TABLE 17
Manifold Pressure in. wg.
5501 - 6500 ft 6501 - 7500 ft
Low High Low
Fire Fire Fire
1.5 3.2 1.5
4.0 9.1 3.9
TABLE 18
High Altitude LP/
Propane Burner
Orifice Kit
7501 - 10,000 ft
*11K46
Page 44
Pressure in. w.g
7501 - 10,000 ft
High Low High
Fire Fire Fire
3.1 1.7 3.5
8.9 4.5 10.0
High Altitude Pressure Switch
4501 - 7500 ft 7501 - 10,000 ft
14A47
14A55
14A54
Supply Line
0 - 10,000 ft.
Min Max
4.5 13.0
11.0 13.0
14A50
14A56
14A53