STEP 5: INSTALLING & TESTING GAS PIPING

Connect the gas piping from the meter to the boiler using a 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. See Figure 2.10 for the appropriate gas pipe sizing and example.

Good piping practices should be followed at all times. See Figure 2.11 for a typical gas piping arrangement. All piping must be supported by hangers, not by the boiler or its accessories.

Install a full-sized sediment trap at the low point in gas line upstream of gas valve. Install a non-restrictive lubricated plug valve in the gas line close to the boiler. Install a ground joint union at the gas valve inlet to allow for servicing. Check local codes and utilities for any special requirements and procedures.

Pipe joint compound (pipe dope) must be compatible with the fuel (natural gas or propane) being used.

Maximum Capacity of Pipe in Cubic Feet of Natural Gas per Hour for Gas Pressures of

0.5Psig or Less and a Pressure Drop of 0.3 Inch Water Column (Based on a 0.60 Specific Gravity Gas)

 

Nominal

 

 

 

 

 

 

 

Length of Pipe, Feet

 

 

 

 

 

 

 

Iron Pipe

Internal

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Size,

Diameter,

10

20

30

40

50

60

70

80

90

100

125

150

175

200

 

Inches

Inches

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1/4"

.326

32

22

18

15

14

12

11

11

10

9

8

8

7

6

3/8"

.493

72

49

40

34

30

27

25

23

22

21

18

17

15

14

1/2"

.622

132

92

73

63

56

50

46

43

40

38

34

31

28

26

3/4"

.824

278

190

152

130

115

105

96

90

84

79

72

64

59

55

1"

1.049

520

350

285

245

215

195

180

170

160

150

130

120

110

100

1-1/4"

1.380

1,050

730

590

500

440

400

370

350

320

305

275

250

225

210

1-1/2"

1.610

1,600

1,100

890

760

670

600

560

530

490

460

410

380

350

320

2"

2.067

3,050

2,100

1,650

1,450

1,270

1,150

1,500

990

930

870

780

710

650

610

2-1/2"

2.469

4,800

3,300 2,700

2,300

2,000

1,850

1,700

1,600

1,500

1,400

1,250

1,130

1,050

980

3"

3.026

8,500

5,900

4,700

4,100

3,600

3,250

3,000

2,800

2,600

2,500

2,200

2,000

1,850

1,700

 

4"

4.026

17,500

12,000

9,700

8,300

7,400

6,800

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 Water Column Inlet Pressure)

(Based on a Pressure Drop of 0.5 Inch Water Column)

Nominal

 

 

 

 

 

Length of Pipe, Feet

 

 

 

 

Iron Pipe

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Size,

10

20

30

40

50

60

70

80

90

100

125

150

Inches

 

 

 

 

 

 

 

 

 

 

 

 

1/2"

275

189

152

129

114

103

96

89

83

78

69

63

3/4"

567

393

315

267

237

217

196

185

173

162

146

132

1"

1071

732

590

504

448

409

378

346

322

307

275

252

1-1/4"

2205

1496

1212

1039

937

834

771

724

677

630

567

511

1-1/2"

3307

2299

1858

1559

1417

1275

1180

1086

1023

967

866

787

2"

6221

4331

3465

2992

2646

2394

2205

2047

1921

1811

1606

1498

Example: Boiler Model GB250-7 is to be installed. The distance from the existing gas meter installation site is 20 feet. What pipe size must be used? The local utility indicates the heating value of the natural gas being supplied is 1,000 Btu per cubic foot. Determine the cubic feet of gas per hour for above boiler model:

300,000 Btu per hour

= 300 cu. ft. per hour

1,000 Btu per cu. ft.

 

1.Find 20 ft. in the upper portion of the table for natural gas under Length of Pipe, Feet heading.

2.Moving down the column, match the required capacity. The higher capacity is acceptable. In our case, it is 350 cu. ft.

3.Move to the left-hand column Nominal Iron Pipe Size, Inches to read required pipe size. In our case, it is 1".

FIGURE 2.10

10