Gas Piping - AHRI APEX Installation, Operating And Service Instructions

VII. Gas Piping
Explosion Hazard. Failure to properly pipe gas
supply to boiler may result in improper operation
and damage to the boiler or structure. Always
assure gas piping is absolutely leak free and of
the proper size and type for the connected load.
An additional gas pressure regulator may be
needed. Consult gas supplier.
NOTICE
Size corrugated stainless steel tubing (CSST)
to ensure proper capacity and minimize flow
restrictions.
A. Size gas piping. Design system to provide
adequate gas supply to boiler. Consider
these factors:
Table 16A: Maximum Capacity of Schedule 40 Black Pipe in CFH* (Natural Gas) For Gas Pressures
of 1/2 psi (3.4 kPa) or Less
Inlet Pressure 13.8 in wc (3.4 kPa)or less; 0.3 in wc (0.07 kPa) Pressure Drop
Nominal Pipe Inside
Size, In. Diameter, In.
½ 0.622
¾ 0.824
1 1.049
1¼ 1.380
1½ 1.610
2 2.067
2½ 2.469
3 3.068
Inlet Pressure 13.8 in wc (3.4 kPa) or less; 0.5 in wc (0.12 kPa) Pressure Drop
Nominal Pipe Inside
Size, In. Diameter, In.
½ 0.622
¾ 0.824
1 1.049
1¼ 1.380
1½ 1.610
2 2.067
2½ 2.469
3 3.068
* 1 CFH of Natural Gas is approximately equal to 1 MBH; contact your gas supplier for the actual heating value of your
gas.
WARNING
10 20
131 90
273 188
514 353
1056 726
1582 1087
3046 2094
4856 3337
8584 5900
10 20
172 118
360 247
678 466
1392 957
2085 1433
4016 2760
6401 4400
11316 7778
1. Allowable pressure drop from point of
delivery to boiler.
pressure is ½ psig (3.4 kPa). Actual point of delivery
pressure may be less; contact gas supplier for
additional information. Minimum gas valve inlet
pressure is printed on the rating label located in the
boiler's vestibule compartment.
2. Maximum gas demand.
input as printed on its rating label. Also consider
existing and expected future gas utilization
equipment (i.e. water heater, cooking equipment).
3. Length of piping and number of fittings.
Refer to Tables 16A (natural gas) or 16B (LP gas)
for maximum capacity of Schedule 40 pipe. Table
17 lists equivalent pipe length for standard fittings.
4. Specific gravity of gas.
gas with a specific gravity of 0.60 can be sized
directly from Table 16A and gas with a specific
gravity of 1.5 can be sized from Table 16B, unless
authority having jurisdiction specifies a gravity
factor be applied. For other specific gravity, apply
gravity factor from Table 18. If exact specific
gravity is not shown choose next higher value.
Length of Pipe, Ft.
30 40 50
72 62 55
151 129 114
284 243 215
583 499 442
873 747 662
1681 1439 1275
2680 2294 2033
4738 4055 3594
Length of Pipe, Ft.
30 40 50
95 81 72
199 170 151
374 320 284
768 657 583
1151 985 873
2217 1897 1681
3533 3024 2680
6246 5345 4738
Maximum allowable system
Refer to the boiler's
Gas piping systems for
60 70 80
50 46 42
104 95 89
195 179 167
400 368 343
600 552 514
1156 1063 989
1842 1695 1576
3256 2996 2787
60 70 80
65 60 56
137 126 117
257 237 220
528 486 452
791 728 677
1523 1402 1304
2428 2234 2078
4293 3949 3674
90 100
40 38
83 79
157 148
322 304
482 455
928 877
1479 1397
2615 2470
90 100
52 50
110 104
207 195
424 400
635 600
1223 1156
1950 1842
3447 3256
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