Page 53
31-5000724 Rev. 0
Proper Combustion
Furnace should operate 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 100 ppm.
Unit
CO
2
% for Nat
CO
2
% for L.P.
All
7.6 - 8.6
9.1 - 10.0
Table 25. High Fire
Unit
CO
2
% for Nat
CO
2
% for L.P.
070
5.7
7.2 - 8.2
090
5.3 - 6.3
6.8 - 7.8
110
135
Table 26. Low Fire
High Altitude
NOTE:
In Canada, certification for installations at
elevations over 4500 feet (1372 m) is the jurisdiction of
local authorities.
NF97DM units require no manifold pressure adjustments
for operation at altitudes up to 10,000 feet (3048m) above
sea level. Units installed at altitude of 7,501 to 10,000 feet
(2287 to 3048m) require a pressure switch change per Table
28. Table 28 also lists gas conversion kit requirements at
all altitudes.
The combustion air pressure switch is factory-set and
requires no adjustment.
Model
Input
Size
LP/Propane Kit High Altitude Pressure Switch
Kit
0 - 10,000
(0-3048 m)
0 - 7,500
(0 - 2286 m)
7,501 - 10,000
(2287 - 3048m)
70
68W77
Not required
14T67
90
110
Table 27. Conversion Kit Requirements
Firing
Rate
Manifold Pressure Nat Gas
Manifold Pressure LP/Propane
Operating Pressure Signal (Delta P)
Min
Normal
Max
Min
Normal
Max
Min
Normal
Max
40%
0.5
0.6
0.7
1.3
1.6
1.9
0.25
0.30
0.35
70%
1.7
1.9
2.1
5.1
5.5
5.9
0.60
0.65
0.70
100%
3.2
3.5
3.8
9.5
10.0
10.5
1.10
1.15
1.20
NOTE:
The values given in table are measurements only. The gas valve should NOT be adjusted.
NOTE
:
A natural to LP/propane gas changeover kit (Table 28) is necessary to convert this unit. Refer to the changeover kit
installation instructions for the conversion procedure.
Table 28. Manifold and Operating Signal Pressures in inches 0-7500 ft (0-2286 m)