Form I-UDB, P/N 202658 R10, Page 13
Gas Connection Size
Capacity of Piping
Cubic Feet per Hour based on 0.3" w.c. Pressure Drop
Specific Gravity for Natural Gas -- 0.6 (Natural Gas -- 1000 BTU/Cubic Ft)
Specific Gravity for Propane Gas -- 1.6 (Propane Gas -- 2550 BTU/Cubic Ft)
Length
Diameter of Pipe
of
1/2"
3/4"
1"
1-1/4"
1-1/2"
2"
Pipe
Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane
20'
92
56
190
116
350
214
730
445
1100
671
2100
1281
30'
73
45
152
93
285
174
590
360
890
543
1650
1007
40'
63
38
130
79
245
149
500
305
760
464
1450
885
50'
56
34
115
70
215
131
440
268
670
409
1270
775
60'
50
31
105
64
195
119
400
244
610
372
1105
674
70'
46
28
96
59
180
110
370
226
560
342
1050
641
80'
43
26
90
55
170
104
350
214
530
323
990
604
90'
40
24
84
51
160
98
320
195
490
299
930
567
100'
38
23
79
48
150
92
305
186
460
281
870
531
125'
34
21
72
44
130
79
275
168
410
250
780
476
150'
31
19
64
39
120
73
250
153
380
232
710
433
175'
28
17
59
36
110
67
225
137
350
214
650
397
200'
26
16
55
34
100
61
210
128
320
195
610
372
Note: When sizing supply lines, consider possibilities of future expansion and increased requirements.
Refer to National Fuel Gas Code for additional information on line sizing.
Sizing Gas Supply
Line
Gas Connection (inches)
Size
Natural
Propane
30, 45, 60, 75, 100, 125, 150, 175, 200
1/2
1/2
225, 250, 300, 350, 400
3/4
3/4
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FIGURE 9 - Gas
connection is at
the pipe nipple that
extends outside the
cabinet.
Illustration shows
both a vertical and
horizontal gas supply;
requirements are the
same.
NOTE:
Gas Conversion Kits
are available for changing
from propane gas to
natural gas or natural gas
to propane gas. A factory-
authorized conversion kit
MUST be used.
6.1.2 Valve Outlet
or Orifice Pressure
Setting
Measuring valve outlet gas pressure cannot be done until the heater is in operation. It
is included in the steps of the “Check-Test-Start” procedure in Paragraph 9. The follow-
ing warnings and instructions apply.
WARNING: Valve outlet gas pressure must never exceed 3.5”
w.c. for natural gas and 10” w.c. for propane gas.
For Natural Gas:
When the heater leaves the factory, the combination gas valve is set
so that the valve outlet gas pressure for a single-stage valve or high fire of a two-stage
valve is regulated to 3.5” w.c. Low fire on a two-stage valve is set to 1.8” w.c. Inlet sup-
ply pressure to the valve for natural gas must be a minimum of 5” w.c. or as noted on
the rating plate and a maximum of 14” w.c.
For Propane Gas:
When the heater leaves the factory, the combination gas valve is
set so that the valve outlet gas pressure for a single-stage valve or high fire of a two-
stage valve is regulated to 10” w.c. Low fire on a two-stage valve is set to 5.0” w.c.
Inlet supply pressure to the valve for propane gas must be a minimum of 11” w.c. and
a maximum of 14” w.c.
