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Proper Cumbustion
Furnace should operate minimum 15 minutes with correct 
-
   
and compare to the table below.
TABLE 20 
EL297
Model
CO
2
% For Nat CO
2
% For L.P
Low Fire High Fire Low Fire High Fire
045 5.4 - 6.4 7.5 - 8.5 6.4 - 7.4 8.8 - 9.8
070 5.3 - 6.3 7.4 - 8.4 6.3 - 7.3 8.7 - 9.7
090 5.8 - 6.8 7.6 - 8.6 6.8 - 7.8 8.9 - 9.9
110 6.1 - 7.1 8.0 - 9.0 7.1 - 8.1 9.3 - 10.3
135 6.1 - 7.1 7.8 - 8.8 7.1 - 8.2 9.1 - 10.1
The maximum carbon monoxide reading should not exceed 100ppm.
High Altitude
NOTE - In Canada, certication 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. See TABLE 21 for de-rate manifold values. Units 
change. Units installed at altitude of 4501 - 10,000 feet 
require a pressure switch change which can be ordered 
separately. TABLE 22 lists conversion kit and pressure 
switch requirements at varying altitudes.
The combustion air pressure switch is factory-set and re-
quiresno adjustment.
TABLE 21 
Manifold and Supply Line Pressure 0-10,000ft.
Unit Gas
Manifold Pressure in. wg. Supply Line 
Pressure in. w.g 
0 - 10,000 ft.
0 - 4500 ft 4501 - 5500 ft. 5501 - 6500 ft 6501 - 7500 ft 7501 - 10,000 ft
Low 
Fire
High 
Fire
Low 
Fire
High 
Fire
Low 
Fire
High 
Fire
Low 
Fire
High 
Fire
Low 
Fire
High 
Fire
Min Max
All 
Sizes
Natuarl 1.7 3.5 1.6 3.3 1.5 3.2 1.5 3.1 1.7 3.5 4.5 13.0
LP/ 
Propane
4.5 10.0 4.2 9.4 4.0 9.1 3.9 8.9 4.5 10.0 11.0 13.0
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.
TABLE 22 
LP/Propane Conversion Kit and Pressure Switch Requirements at Varying Altitudes
Unit
Natural to
LP/Propane
High Altitude 
Natural Burner 
High Altitude LP/
Propane Burner 
High Altitude Pressure Switch
0 - 7500 ft 7501 - 10,000 ft 7501 - 10,000 ft 4501 - 7500 ft 7501 - 10,000 ft
045
*11K51 73W37 *11K46
14A51 14A53
070 14A48 14A54
090 14A54 14A53
110 25B93 14A45
135 25B94 25B95
* 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).