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STEP 4: INSTALLING & TESTING GAS PIPING
➤ PROCEDURE A: Select gas pipe size which will result in a pressure drop of less than 0.3" W.C.
for natural gas or 0.5" W.C. for propane, following example below.
Example: Boiler Model EW-125 is to be installed. Distance from existing gas meter to installation site is 20 ft.
What pipe size must be used? Local utility indicates heating value of natural gas being supplied is 1020 Btu per
cu.ft. Determine cubic feet of gas per hour for above boiler model:
125,000 Btu per hour = 122.5 cu.ft. per hour
1020 Btu per cu.ft.
1. Find 20 ft. in upper portion of the table for natural gas under “Length of Pipe, Feet” heading.
2. Moving down the column, match required capacity. Higher capacity acceptable. In our case it is 190 cu.ft.
3. Move to left-hand column “Nominal Iron Pipe Size, Inches”; read required pipe size. In our case it is 3/4
4. Take into account the effects of pipe fittings when determining the correct pipe size.
Maximum Capacity of Pipe in Cubic Feet of Natural Gas per Hour for Gas Pressures of
0.5 Psig or Less and a Pressure Drop of 0.3 Inch Water Column
(Based on a 0.60 Specific Gravity Gas)
Nominal
Iron Pipe Internal
Size, Diameter,
Inches
Inches
1/4"
3/8"
1/2"
3/4"
1"
1-1/4"
1-1/2"
2"
2-1/2"
3"
4"
.326
.493
.622
.824
1.049
1.380
1.610
2.067
2.469
3.026
4.026
Length of Pipe, Feet
10
20
30
40
50
60
32
22
72
49
132
92
278
190
520
350
1,050
730
1,600 1,100
3,050 2,100
4,800 3,300
8,500 5,900
17,500 12,000
18
40
73
152
285
590
890
1,650
2,700
4,700
9,700
15
34
63
130
245
500
760
1,450
2,300
4,100
8,300
14
30
56
115
215
440
670
1,270
2,000
3,600
7,400
12
27
50
105
195
400
600
1,150
1,850
3,250
6,800
70
80
90
100
125
150
175
200
11
11
10
9
8
8
7
6
25
23
22
21
18
17
15
14
46
43
40
38
34
31
28
26
96
90
84
79
72
64
59
55
180
170
160
150
130
120
110 100
370
350
320
305
275
250
225 210
560
530
490
460
410
380
350 320
1,500
990
930
870
780
710
650 610
1,700 1,600 1,500 1,400 1,250 1,130 1,050 980
3,000 2,800 2,600 2,500 2,200 2,000 1,850 1,700
6,200 5,800 5,400 5,100 4,500 4,100 3,800 3,500
Maximum Capacity of Pipe in Thousands of Btu per Hour of Undiluted Liquefied
Petroleum gases (at 11 Inches of Water Column Inlet Pressure)
(Based of a Pressure Drop of 0.5 Inch Water Column)
Nominal
Iron Pipe
Size,
Inches
1/2"
3/4"
1"
1-1/4"
1-1/2"
2"
Length of Pipe, Feet
10
275
567
1071
2205
3307
6221
20
30
189 152
393 315
732 590
1496 1212
2299 1858
4331 3465
40
50
60
129
114
267
237
504
448
1039
937
1559 1417
2992 2646
103
217
409
834
1275
2394
70
80
96
89
196 185
378 346
771 724
1180 1086
2205 2047
90
100
83
78
173 162
322 307
677 630
1023 967
1921 1811
125
150
69
146
275
567
866
1606
63
132
252
511
787
1498
FIGURE 1.16
10