Rinnai RU80i Installation And Operation Manual page 42


Any compound used on the threaded joint of the
gas piping shall be a type which resists the action
of liquefied petroleum gas (propane / LPG).

The gas supply line shall be gas tight, sized, and so
installed as to provide a supply of gas sufficient to
meet the maximum demand of the heater and all
other gas consuming appliances at the location
without loss of pressure.
INFORMATION

Refer to an approved pipe sizing chart if in doubt
about the size of the gas line.
Size the gas pipe
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 siz-
ing 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 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 heating value of the gas
(available from the local gas company). The gas
input needs to include all gas products at the lo-
cation 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
Cubic Feet Gas Input of all gas products (BTU / HR)
per Hour =
Heating Value of Gas (BTU / FT
(CFH)
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
3
1000 BTU/FT . The gas input of the RU98i 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
length is 10 feet then the 3/4 inch pipe size is capable
3
of supplying 264 FT /HR of natural gas.
42
3
)
3
/HR. If the pipe
KB Series Manual
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
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
Length
1/2
10 291
20 200
30 160
40 137
50 122
60 110
80 101
100 94
Pipe Size (inches)
1 1 1/4
514 1060
353 726
284 583
243 499
215 442
195 400
179 368
167 343
157 322
148 304
Pipe Size (inches)
3/4 1 1 1/4
608 1150
418 787
336 632
287 541
255 480
231 434
212 400
197 372
1 1/2
1580
1090
873
747
662
600
552
514
482
455
2350
1620
1300
1110
985
892
821
763