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Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. Table 10 shows acceptable combustion for ALL
EL280UH models. The maximum carbon monoxide
reading should not exceed 100 ppm
TABLE 10
Firing Rate
CO
High Fire
Low Fire
Manifold Pressure in.
Unit
Gas
Input
Low Firer
Natural
070
LP/propane
3
Natuarl
090
LP/propane
3
Natural
110
LP/propane
3
Natural
135
LP/propane
3
1
This is the only permissible derate for these units.
2
Natural gas high altitude orifice kit required.
3
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.
NOTE - Units may be installed at altitudes up to 4500 ft. above sea level without modifications
High Altitude Pressure Switch Kit
Unit Input
0-4500 ft
070
090
No Change
110
135
NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruc-
tion for the conversion procedure.
% Nat
CO
% LP
2
2
6.0 - 7.5
7.0 - 8.5
5.0 - 6.5
5.8 - 7.3
Manifold Pressure Settings
wg. 0 - 4500 ft
High Fire
Low Fire
1.7
3.5
4.9
10.0
1.7
3.5
4.9
10.0
1.7
3.5
4.9
10.0
1.7
3.5
4.9
10.0
Pressure Switch and Gas Conversion Kits at all Altitudes
4501- 7500 ft
7501-10,000 ft
91W53
73W35
91W53
73W35
91W53
73W35
73W33
73W34
High Altitude
The manifold pressure may require adjustment and com-
bustion air pressure switch may need replacing to ensure
proper combustion at higher altitudes. Refer to table 11
for manifold pressure and table 12 for pressure switch
change and gas conversion kits.
TABLE 11
Manifold Pressure in.
wg. 4500 - 7500 ft
High Fire
1.6
3.4
4.9
10.0
1.5
3.2
4.9
10.0
1.5
2.8
4.9
10.0
1.5
2.8
4.9
10.0
TABLE 12
High Altitude
Natural Gas Kit
7501-10,000 ft
73W37
Page 31
Manifold Pressure in. wg.
7500 - 10,000 ft
2
Low Fire
High Fire
1.7
3.5
4.9
10.5
1.7
3.5
4.9
10.0
1.7
3.5
4.9
10.0
1.7
3.5
4.9
10.0
.
LP/Propane Gas Kit
7501 - 10,000
0-7500 ft
ft
11K51
11K46
Supply Line
Pressure
in. w.g.
Min
Max
4.5
13.0
11.0
13.0
4.5
13.0
11.0
13.0
4.5
13.0
11.0
13.0
4.5
13.0
11.0
13.0
LP/Propane to
Natural Kit
0 -7500 ft
77W09
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