Rinnai Demand Duo R Series Installation And Operation Manual page 28

The gas supply must be capable of handling the
entire gas load required 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.
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.
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
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is 1000 BTU/FT . The gas input of the
CHS19980R is 199,000 BTU/HR. Additional
appliances at the location require 65,000 BTU/hr.
Therefore the cubic feet per hour = (199,000 +
65,000) / 1000 = 264 FT
10 feet then the 3/4 inch pipe size is capable of
3
supplying 264 FT /HR of natural gas.
Gas Input of all gas products (BTU/HR)
(CFH) =
Heating Value of Gas (BTU/FT
Demand Duo™ R-Series Installation and Operation Manual
3
/HR. If the pipe length is
3
)
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
Cubic Feet per Hour (CFH)
Pipe Size (inches)
Length
3/4
10 273
20 188
30 151
40 129
50 114
60 104
70 95
80 89
90 83
100 79
Pipe Sizing Table - Propane Gas
Schedule 40 Metallic Pipe
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
Capacity in Thousands of BTU per Hour
Pipe Size (inches)
Length
1/2 3/4
10 291 608
20 200 418
30 160 336
40 137 287
50 122 255
60 110 231
80 101 212
100 94 197
1 1 1/4 1 1/2
514 1,060 1,580
353 726 1,090
284 583 873
243 499 747
215 442 662
195 400 600
179 368 552
167 343 514
157 322 482
148 304 455
1 1 1/4
1,150 2,350
787 1,620
632 1,300
541 1,110
480 985
434 892
400 821
372 763
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