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Installation
Table 13. Sizing natural gas pipe mains and branches
Gas SupplyPipe Run (ft)
10
20
30
40
50
60
70
80
90
100
125
150
175
200
Notes:
1.
Table is based upon specific gravity of 0.60. Refer to the latest edition of the National Fuel Gas Code, Z223.1, unless superseded by local gas codes.
2.
If more than one unit is served by the same main gas supply, consider the total gas input (cubic feet/hr.) and the total length when determining the appropriate gas
pipe size.
3.
Obtain the Specific Gravity and BTU/Cu.Ft. from the gas company.
4.
The following example demonstrates the considerations necessary when determining the actual pipe size:
Example: A 40' pipe run is needed to connect a unit with a 850 MBH furnace to a natural gas supply having a rating of 1,000 BTU/Cu.Ft. and a specific gravity of
0.60
Cu.Ft/Hour = Furnace MBH Input
Gas BTU/Cu.Ft. X Multiplier
Cu.Ft/Hour = 850
The above table indicates that a 2" pipe is required.
Table 14. Specific gravity multipliers
Specific
Gravity
Multiplier
0.50
1.10
0.55
1.04
0.60
1.00
0.65
0.96
Table 15. Natural gas – high altitude gas input rating reduction orifice chart
Heater size (MBh)
250
350
500
850
1200
Note: Orifice sizes required to reduce input ratings by 4% per every 1000' above 2000' per the National Fuel Gas Code Z223.1.
44
1¼" Pipe
1½" Pipe
1,060
1,580
1,090
726
583
873
499
747
442
662
400
600
368
552
343
514
322
482
304
455
269
403
244
366
224
336
209
313
Table 14, p. 44
0-2000'
3000'
4000'
#34
#36
#36
#32
#34
#35
#34
#36
#36
#34
#36
#36
3.00 mm
#34
#35
Gas Input (Cubic Feet/Hour)
2" Pipe
2½" Pipe
3,050
4,860
2,090
3,340
1,680
2,680
1,440
2,290
1,280
2,030
1,160
1,840
1,060
1,690
1,580
989
1,480
928
877
1,400
1,240
777
1,120
704
1,030
648
602
960
5000'
6000'
7000'
#37
#37
#38
#35
#36
#36
#37
#37
#38
#37
#37
#38
#35
#36
#36
3" Pipe
4" Pipe
8,580
17,500
5,900
12,000
4,740
9,660
4,050
8,270
3,590
7,330
3,260
6,640
3,000
6,110
2,790
5,680
2,610
5,330
2,470
5,040
2,190
4,460
1,980
4,050
1,820
3,720
1,700
3,460
8000'
9000'
10000'
#39
#40
#42
#37
#38
#40
#39
#40
#42
#39
#40
#42
#37
#38
#40
RT-SVX063G-EN
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