Page 28
506178−01 05/2009
Gas Pressure Adjustment
Gas Flow (Approximate)
1 − Operate unit at least 15 minutes before checking gas
flow. Determine the time in seconds for one revolu-
tions of gas through the meter. A portable LP gas me-
ter (17Y44) is available for LP applications.
TABLE 14
Gas Flow Rate (Ft.
3
/Hr.)
Seconds for 1
Gas Meter Size
Seconds for 1
Revolution
1/2 cu ft Dial
1 cu ft Dial
10
180
360
12
150
300
14
129
257
16
113
225
18
100
200
20
90
180
22
82
164
24
75
150
26
69
138
28
64
129
30
60
120
32
56
113
34
53
106
36
50
100
38
47
95
40
45
90
42
43
86
44
41
82
46
39
78
48
38
75
50
36
72
52
35
69
54
33
67
56
32
64
58
31
62
60
30
60
2 − Compare the number of seconds and the gas meter
size in table 14 to determine the gas flow rate. Multiply
the gas flow rate by the heating value to determine the
unit input rate. If manifold pressure is correct and the
unit input rate is incorrect, check gas orifices for proper
size and restriction.
3 − Remove temporary gas meter if installed.
NOTE − To obtain accurate reading, shut off all other gas
appliances connected to meter.
Gas Pressure
1 − Check the gas line pressure with the unit firing at maxi-
mum rate. A minimum of 4.5 in. w.c. for natural gas or
11.0 in. w.c. for LP/propane gas should be maintained.
2 − After the line pressure has been checked and ad-
justed, check the low fire and high fire manifold pres-
sures. See figures 20 and 21 for the location of the
manifold pressure adjustment screws. Low and high
fire manifold pressures are given in table 15. A natural
gas to LP/propane gas changeover kit is required to
convert the unit.
High Altitude Information
Refer to table 15 for high altitude requirements and man-
ifold pressure settings at all altitudes.
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
NOTE − 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.
TABLE 15
High Altitude Requirements / Manifold Pressure Settings
Altitude
Manifold Pressure
Model
Input
Gas
0 − 7500 ft.
(0 − 2285 m)
7501−10,000 ft.
(2286 − 3048 m)
Manifold Pressure
at all altitudes
Input
Size
Gas
Required
Pressure
Required
Pressure
Low Fire
High Fire
Required
Conversion Kit
Pressure
Switch
Required
Conversion Kit
Pressure
Switch
in. w.g.
kPa
in. w.g.
kPa
−070, −090,
Nat.
N/A
No Change
44W51
44W31
1.7
0.42
3.5
0.87
−070, −090,
−110
LPG
44W48
No Change
44W50
44W31
4.9
1.22
10.0
2.5
Pressure switch is factory set. No adjustment necessary. All models use the factory installed pressure switch from 0−7500 feet (0−2285 m).
