Proper Combustion; High Altitude - Lennox MERIT ML193UH 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 tables below.
TABLE 13
ML193
Unit
−045
−070
−090
−110
−135
The maximum carbon monoxide reading should not exceed 50 ppm.
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
Natural to
LP/Propane
ML193
Unit
0 − 7500 ft
(0 − 2286m)
−045
−070
−090
*69W73
−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).
CO % CO %
2 For Nat 2 For L.P.
7.2 − 7.9 8.6 − 9.3

High Altitude

Natural Burner
Orifice Kit
7501 − 10,000 ft
(2286 − 3038m)
73W37
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
LP/Propane High Altitude
to LP/Propane
Natural Burner Orifice Kit
0 − 7500 ft 7501 − 10,000 ft
(0 − 2286m) (2286 − 3038m)
*73W81 *68W68
Page 44
High Altitude Pressure Switch
4501 − 7500 ft 7501 −10,000 ft
(1373 − 2286m) (2286 − 3048m)
93W87 93W88