Installation Piping
RT-SVX34F-EN
37
Table 18.
Sizing natural gas pipe mains and branches
Gas Input (Cubic Feet/Hour)*
Gas Supply Pipe
Run (ft)
1-1/4” Pipe 1-1/2” Pipe
2" Pipe
2-1/2” Pipe
3"Pipe
4"Pipe
10
1050
1600
3050
4800
8500
17500
20
730
1100
2100
3300
5900
12000
30
590
890
1650
2700
4700
9700
40
500
760
1450
2300
4100
8300
50
440
670
1270
2000
3600
7400
60
400
610
1150
1850
3250
6800
70
370
560
1050
1700
3000
6200
80
350
530
990
1600
2800
5800
90
320
490
930
1500
2600
5400
100
305
460
870
1400
2500
5100
125
275
410
780
1250
2200
4500
150
250
380
710
1130
2000
4100
175
225
350
650
1050
1850
3800
200
210
320
610
980
1700
3500
Notes:
1.
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.
2.
Obtain the Specific Gravity and BTU/Cu.Ft. from the gas company.
3.
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 500 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
Table 17, p. 36
Cu.Ft/Hour = 500
Table 18
indicates that a 1-1/4” pipe is required.
*Table is based on a specific gravity of 0.60. Use
Table 17, p. 36
or the specific gravity of the local gas supply.
Figure 33.
Gas train configuration for low heat units
(high heat units utilize two gas trains.)