Installation Manual
Demand Duo™ R-Series Installation and Operation Manual 28
Length
Pipe Size (inches)
3/4 1 1 1/4 1 1/2
10 273 514 1,060 1,580
20 188 353 726 1,090
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
Pipe Sizing Table - Natural Gas
Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.
Specific Gravity: 0.60
Schedule 40 Metallic Pipe
Cubic Feet per Hour (CFH)
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
is 1000 BTU/FT
3
. 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
3
/HR. If the pipe length is
10 feet then the 3/4 inch pipe size is capable of
supplying 264 FT
3
/HR of natural gas.
Gas Input of all gas products (BTU/HR)
Heating Value of Gas (BTU/FT
3
)
(CFH) =
Length
Pipe Size (inches)
1/2 3/4 1 1 1/4
10 291 608 1,150 2,350
20 200 418 787 1,620
30 160 336 632 1,300
40 137 287 541 1,110
50 122 255 480 985
60 110 231 434 892
80 101 212 400 821
100 94 197 372 763
Pipe Sizing Table - Propane Gas
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Specific Gravity: 1.50
Schedule 40 Metallic Pipe
Capacity in Thousands of BTU per Hour