26
PROPER COMBUSTION
HIGH ALTITUDE
Furnace should operate a minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Take combustion sample beyond the flue outlet
and compare to the tables below. The maximum carbon
monoxide reading should not exceed 50 ppm.
Table 3
Unit
CO
2
% For Nat
CO
2
% For L.P.
-070
6.3 - 7.8
7.0 - 9.0
-090
-110
-135
The manifold pressure may require adjustment and
combustion air pressure switch may need replacing to
ensure proper combustion at higher altitudes. Refer to table
4 for manifold pressure and Table 5 for pressure switch
change and gas conversion kits.
For safety, shut unit off and remove
manometer as soon as an accurate reading
has been obtained. Take care to replace
pressure tap plug.
IMPORTANT
!
Table 4
Manifold Pressure Settings at all Altitudes
Model
Input
Size
Gas
0-610m*
(0-2000 ft)
611-914m*
(2001-3000 ft)
915-1219m*
(3001-4000 ft)
1220-1524m*
(4001-5000 ft)
1525-1981m*
(5001-6500 ft)
Line
Pressure
(kPa)
Min
Max
All
Models
Nat
0.87
0.72
0.67
0.62
0.87
1.12 3.20
LP/propane
2.30
2.30
2.19
2.12
2.30
2.74 3.20
* See table 5 for proper high altitude gas conversion kit.
