Rinnai REU-VA3237FFU - Manual (Page 20)

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.