Rinnai . REU-VC2025FFU-US, Installation And Operation Manual

Page: 19 / 80

Value Series Manual 19
Size the gas pipe
The gas supply must be capable of handling the en re
gas load at the loca on. 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 siz ‐
ing in the United States, refer to the Na onal Fuel Gas
Code, NFPA 54 . The below informa on is provided as
an example. The appropriate table from the applica ‐
ble 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 hea ng value of the gas
(available from the local gas company). The gas
input needs to include all gas products at the lo ‐
ca on 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
fi nd 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 hea ng value of natural gas for your loca on is
1000 BTU/FT
3
. The gas input of the V75i is 180,000
BTU/HR. Addi onal appliances at the loca on require
65,000 BTU/hr. Therefore the cubic feet per hour =
(180,000 + 65,000) / 1000 = 245 FT
3
/HR. If the pipe
length is 10 feet then the 3/4 inch pipe size is capable
of supplying 273 FT
3
/HR of natural gas.
Gas Input of all gas products (BTU / HR)
Hea ng Value of Gas (BTU / FT
3
)
Cubic Feet
per Hour =
(CFH)
•
Any compound used on the threaded joint of the
gas piping shall be a type which resists the ac on
of lique fi ed petroleum gas (propane / LPG).
•
The gas supply line shall be gas ght, sized, and so
installed as to provide a supply of gas su ffi cient to
meet the maximum demand of the heater and all
other gas consuming appliances at the loca on
without loss of pressure.
INFORMATION
•
Refer to an approved pipe sizing chart if in doubt
about the size of the gas line.
Length
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
Pipe Sizing Table ‐ Natural Gas
Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.
Speci fi c Gravity: 0.60
Schedule 40 Metallic Pipe
cubic feet per hour
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
Pipe Sizing Table ‐ Propane Gas
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Speci fi c Gravity: 1.50
Schedule 40 Metallic Pipe
Capacity in Thousands of BTU per Hour