Rinnai RC80HPI - Manual (Page 20)

20 Manual - Rinnai Condensing Water Heaters
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.
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. 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.
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
Length 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
Pipe Sizing Table - Natural Gas Pipe Sizing Table - Propane Gas
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
Capacity in Thousands of BTU per Hour