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INSTALLATION INSTRUCTIONS
Gas Piping
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. For gas pipe
sizing in the United States, refer to the National Fuel
Gas Code, NFPA 54. For Canadian gas pipe sizing,
refer to the Natural Gas and Propane Installation Code
CAN/CSA B149.1. The information below is provided as
an example. The appropriate table from the applicable
code must be used.
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.
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 propane gas for
your location is 2500 BTU/FT
3
. The gas input of the
tankless water heater is 199,900 BTU/HR. Additional
appliances at the location require 75,000 BTU/HR.
Therefore, the cubic feet per hour =
(199,900 + 75,000)/2500 = 109 FT
3
/HR. If the
pipe length is 100 ft., then the 3/4-inch pipe size
capable of supplying 197 FT
3
/HR of propane gas will
be adequate.
Gas Input of
Cubic Feet Water Heater (BTU/HR)
Per Hour (CFH) = Heating Value of Gas (BTU/FT
3
)
Pipe-Sizing Table – Natural Gas
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
(Capacity in cubic feet per hour)
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
Pipe-Sizing Table – Propane Gas
Schedule 40 Metallic Pipe
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
(Capacity in cubic feet per hour)
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
This is an example, in US, refer to current National Fuel Gas
Code, NFPA 54 for correct pipe sizing chart, and in Canada,
refer to current CAN/CSA B149.1.
Gas Supply
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