Rinnai RH180 Operation And Installation Manual page 25

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 sup-
plied, and gas line type. For gas pipe sizing in the United
States, refer to the Na onal Fuel Gas Code, NFPA 54. The
below informa on is provided as an example. The appro-
priate 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 hea ng value of the gas (available from the
local gas company). The gas input needs to include all
gas products at the loca 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 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.
Cubic Feet Gas Input of all gas products (BTU / HR)
per Hour = Hea ng Value of Gas (BTU / FT
Example:
The hea ng value of natural gas for your loca on is 1000
3
BTU/FT . The gas input of the RH180 is 91,500 BTU/HR.
Addi onal appliances at the loca on require 65,000 BTU/
hr. Therefore the cubic feet per hour = (91,500 +
65,000) / 1000 = 156.5 FT
feet then the 3/4 inch pipe size is capable of supplying
3
156.5 FT /HR of natural gas.
3
/HR. If the pipe length is 10
Pipe Sizing Table - Natural Gas
Inlet Pressure:
Pressure Drop:
Specific Gravity:
Length
10
20
30
40
50
60
70
3
)
80
90
100
Pipe Sizing Table - Propane Gas
Inlet Pressure:
Pressure Drop:
Specific Gravity:
Length
10
20
30
40
50
60
80
100
RH180 Manual
Schedule 40 Metallic Pipe
less than 2 psi (55 inches W.C.)
0.3 inches W.C.
0.60
Capacity in Thousands of BTU per Hour
Pipe Size (inches)
1/2 3/4
131 273
90 188
— 151
— 129
— 114
— 104
— 95
— 89
— 83
— 79
Schedule 40 Metallic Pipe
11.0 inches W.C.
0.5 inches W.C.
1.50
Capacity in Thousands of BTU per Hour
Pipe Size (inches)
1/2 3/4
291 608
200 418
160 336
137 287
122 255
110 231
101 212
94 197
1 1 1/4
514 1060
353 726
284 583
243 499
215 442
195 400
179 368
167 343
157 322
148 304
1 1 1/4
1150 2350
787 1620
632 1300
541 1110
480 985
434 892
400 821
372 763
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