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Kenmore 505 User Manual

Page 12

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Pipe Sizing Procedure - Example

The gas supply must be capable of handling the entire gas load at the location. Gas line sizing is based on gas type,
the pressure drop in the system, the gas pressure supplied, and gas line type. Refer to the National Fuel Gas Code,

NFPA54, for proper gas line sizing. The below information is provided as an example.

1. Determine the cubic feet per hour of gas required by dividing the gas input (on the rating plate) by the heating value

of the gas (available from the local gas company). The gas input needs to include all gas products at the location
and the maximum BTU usage at full load when all gas products are in use.

Gas Input of the water heater (BTU / HR)

Cubic Feet per Hour (CFH) =

----------------------------------------------------------

Heating Value of Gas (BTU / FT 3 )

2.

Use the table for your gas type to find the pipe size required for your cubic feet per hour of gas and your pipe

length.

Example: The heating value of natural gas for your location is 1020 BTU/FP

The gas input is 199,000 BTU/HR. Additional appliances at the location require 75,000 BTU/HR.
Therefore the cubic feet per hour = (199,000 + 75,000) / 1020 = 268.6 FP/HR.

If the pipe length is 100 ft then the 1 % inch pipe size capable of supplying 304 FP/HR of natural gas will
be adequate.

TABLE 2: Pipe Sizing Table - Natural Gas

cubic feet per hour Schedule 40 Metallic Pipe

Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.

Specific Gravity: 0.60

Length

Pipe Size (inches)

3/4

1

1 1/4

1 1/2

10

273

514

1060

1580

20

188

353

726

1090

30

151

284

583

873

40

129

243

499

747

50

114

215

442

662

60

104

195

400

600

70

95

179

368

552

80

89

167

343

514

90

83

157

322

482

100

79

148

304

455

125

70

131

269

403

150

63

119

244

366

175

58

109

224

336

200

54

102

209

313

TABLE 3: Pipe Sizing Table - Propane Gas

cubic feet per hour Schedule 40 Metallic Pipe

Inlet Pressure: 11 inches W.C.
Pressure Drop: 0.5 inches W.C.

Specific Gravity: 1.50

Length

Pipe Size (inches)

1/2

3/4

1

1 1/4

10

291

608

1150

2350

20

200

418

787

1620

30

160

336

632

1300

40

137

287

541

1110

50

122

255

480

985

60

110

231

434

892

80

101

212

400

821

100

94

197

372

763

125

89

185

349

716

150

84

175

330

677

175

74

155

292

600

200

67

140

265

543

12

305 & 505 Indoor Manual