Page 44
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.
TABLE 13
ML193
Unit
CO
2
%
For
Nat
CO
2
%
For
L.P.
−045
7.2 − 7.9 8.6 − 9.3
−070
−090
−110
−135
The maximum carbon monoxide reading should not exceed 50 ppm.
High Altitude Information
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
ML193UH units require no manifold pressure adjustments
for operation at altitudes up to 10,000 feet (3048 m) above
sea level. Units installed at altitude of 4501 − 10,000 feet
(1373 to 3048m) require a pressure switch change which
can be ordered separately. Table 14 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 14
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 93W87 93W88
−070
−090
−110
−135
* 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).
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