Pipe Sizing Procedure - Example - Rinnai TANKLESS WATER HEATER V53E Operation And Installation Manual

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 below information is provided as an example. The
appropriate table from the applicable code must be used.
1. For some tables, you will need to determine the cubic feet per hour of gas required by dividing the gas input
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.
Cubic Feet per Hour (CFH) =
2. Use the table for your gas type and pipe type to find the pipe size required. The pipe size must be able to
provide the required cubic feet per hour of gas or the required BTU/hour.
Example: The heating value of natural gas for your location is 1000 BTU/FT
150,000 BTU/HR. Additional appliances at the location require 114,000 BTU/hr. Therefore the cubic
feet per hour = (150,000 + 114,000) / 1000 = 264 FT
pipe size is capable of supplying 264 FT
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
3/4
10 273
20 188
30 151
40 129
50 114
60 104
70 95
80 89
90 83
100 79
125 70
150 63
175 58
200 54
20
Gas Input of all gas products (BTU / HR)
Pipe Size (inches)
1 1 1/4
514 1060
353 726
284 583
243 499
215 442
195 400
179 368
167 343
157 322
148 304
131 269
119 244
109 224
102 209
V53i & V53e Operation and Installation Manual
Heating Value of Gas (BTU / FT
3
/HR. If the pipe length is 10 feet then the 3/4 inch
3
/HR of natural gas.
Pipe Sizing Table - Propane Gas
Inlet Pressure:
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
Capacity in Thousands of BTU per Hour
Length
1 1/2
1580
10
1090 20
873 30
747
40
662
50
600 60
552 80
514
100
482
125
455
150
403 175
366
200
336
313
3
)
3
. The gas input of the V53i is
Schedule 40 Metallic Pipe
11.0 inches W.C.
Pipe Size (inches)
1/2 3/4
291 608 1150
200 418
160 336
137 287
122 255
110 231
101 212
94 197
89 185
84 175
74 155
67 140
1 1 1/4
2350
787 1620
632 1300
541 1110
480 985
434 892
400 821
372 763
349 716
330 677
292 600
265 543