20
VA Series Indoor LS Manual
Pipe Sizing Procedure - 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 Rinnai 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 propane gas for your location is 2516 BTU / FT
3
. The gas input of the R94LSi is
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
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.
Pipe Sizing Table - Natural Gas
Pipe Sizing Table - Propane Gas
Pipe Size (inches)
10
20
30
40
50
60
70
80
90
100
125
150
175
200
3/4
1
1 1/4
1 1/2
273
1060 1580
188
1090
151
873
129
747
114
662
104
600
95
368 552
89
343 514
83
322 482
79
304 455
70
269 403
63
244 366
58
224 336
54
514
353
284
243
215
195
179
167
157
148
131
119
109
102
726
583
499
442
400
209 313
Length
Length
Pipe Size (inches)
10
20
30
40
50
60
80
100
125
150
175
200
s
1/2 3/4 1 1
1/4
291
1150 2350
200
1620
160
1300
137
1110
122
985
110
892
101
821
94
372 763
89
349 716
84
330 677
74
292 600
67
787
632
541
480
434
400
608
418
336
287
255
231
212
197
185
175
155
140 265 543
Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.
Specific Gravity: 0.60
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
Schedule 40 Metallic Pipe
cubic feet per hour
Schedule 40 Metallic Pipe
cubic feet per hour
Gas Piping
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.
