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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 tables below.
The maximum carbon
monoxide reading should not exceed 50 ppm.
TABLE 14
ML193
Unit
CO
2
%
For Nat
CO
2
%
For L.P.
-045
7.2 - 7.9
8.6 - 9.3
-070
-090
-110
High Altitude Information
NOTE
- In Canada, certification for installations at eleva
tions over 4500 feet (1372 m) is the jurisdiction of local au
thorities.
Units may be installed at altitudes up to 10,000 ft. above
sea level. See table 15 for de-rate manifold values. Units
installed at altitude of 7501 - 10,000 feet require an orifice
change. Units installed at altitude of 4501 - 10,000 feet re
quire a pressure switch change which can be ordered sep
arately. Table 16 lists conversion kit and pressure switch
requirements at varying altitudes.
The combustion air pressure switch is factory-set and re
quires no adjustment.
NOTE
- A natural to LP/propane gas changeover kit is nec
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
TABLE 15
Manifold and Supply Line Pressure 0-10,000ft.
ML193
Unit
Gas
Manifold Pressure in. wg.
Supply Line
Pressure
in. w.g.
0 - 10000 ft.
0-4500 ft.
4501-5500 ft.
5501-6500 ft.
6501 -
7500ft.
7501 - 10000ft.
All Sizes
Natural
3.5
3.3
3.2
3.1
3.5
4.5
13.0
LP/propane
10.0
9.4
9.1
8.9
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 16
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
ML193
Unit
Natural to
LP/Propane
High Altitude
Natural Burner
Orifice Kit
LP/Propane
to Natural
High Altitude
LP/Propane
Burner Orifice Kit
High Altitude Pressure
Switch
0 - 7500 ft
(0 - 2286m)
7501 - 10,000 ft
(2286 - 3038m)
0 - 7500 ft
(0 - 2286m)
7501 - 10,000 ft
(2286 - 3038m)
4501 - 7500
ft
(1373 -
2286m)
7501 -10,000
ft
(2286 -
3048m)
-045
*69W73
73W37
*73W81
*68W68
11U65
11U66
-070
-090
-110
* 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).
