Pipe Sizing Procedure - Example - Rinnai REU-VA3237FFU 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. Refer to the National Fuel
Gas Code, NFPA 54, 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.
Cubic Feet per Hour (CFH) =
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 2516 BTU / FT
190,000 BTU/HR. Additional appliances at the location require 75,000 BTU/HR.
Therefore the cubic feet per hour = (190,000+75,000) / 2516 = 105.3 FT
If the pipe length is 100 ft then the 3/4 inch pipe size capable of supplying 197 FT
will be adequate.
Pipe Sizing Table - Natural Gas
cubic feet per hour
Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.
Specific Gravity: 0.60
Length
3/4
10 273
20 188
30 151
40 129
50 114
60 104
70 95
89
80
90 83
79
100
125 70
150 63
175 58
200 54
20
Gas Input of Rinnai water heater (BTU / HR)
Schedule 40 Metallic Pipe
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
VA Series Indoor LS Manual
Heating Value of Gas (BTU / FT
Pipe Sizing Table - Propane Gas
cubic feet per hour
Inlet Pressure:
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
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 R94LSi is
3
/ HR.
3
/ HR of propane gas
Schedule 40 Metallic Pipe
11.0 inches W.C.
Pipe Size (inches)
1/2 3/4
291 608 1150
200 418 787
160 336 632
137 287 541
122 255 480
110 231 434
101 212 400
94 197 372
89 185 349
84 175 330
74 155 292
67 140 265
s
1 1 1/4
2350
1620
1300
1110
985
892
821
763
716
677
600
543