508146-01
Issue 2051
Page 5
4
of 7
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 - 10.1
Table 27. 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 28. Low Fire
High Altitude
NOTE:
In Canada, certification f or i nstallations at
elevations over 4500 feet (1372 m is the jurisdiction of
local authorities.
GUH97M
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
30. Table 30 also lists gas conversion kit requirements at
all altitudes.
The combustion air pressure switch is factory-set and
requires no adjustment.
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
:
installation instructions for the conversion procedure.
Table 29. Manifold and Operating Signal Pressures in inches 0-7500 ft (0-2286 m)
Unit
LP/Propane
Kit
High Altitude Pressure
Switch Kit
Manifold Pressure at All Altitudes (in. w.g.)
Gas Orifice
Size
0 - 10,000
(0 - 3048 m)
0 - 7,500
(0 - 2286 m)
7,501 - 10,000
(2287 - 3048 m)
Low Fire
(35% rate)
High Fire
(100% rate)
Natural
Gas
LP/
Propane
Natural
Gas
LP/Propane
Nat
LP
070
68W77
Not required
14T65
0.40 - 0.60
1.2 - 1.8
3.2 - 3.8
9.5 - 10.5
.0625
.034
090
110
135
NOTE
:
The values given are measurements only. The gas valve should not be adjusted.
Table 30. Conversion Kit Requirements and Manifold Test Pressures