Gas Piping - Rheem RTGH-95DV Use And Care Manual

Gas Piping

Pipe-Sizing Procedure – Example
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 sizing in the United States,
refer to the National Fuel Gas Code, NFPA 54. For
Canadian gas pipe sizing, refer to the Natural Gas
and Propane Installation Code CAN/CSA B149.1.
The information below is provided as an example.
The appropriate table from the applicable code
must be used.
1. Determine the cubic feet per hour of gas
required by dividing the gas input (on the rating
plate) 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.
Cubic Feet Water Heater (BTU/HR)
Per Hour (CFH) = Heating Value of Gas (BTU/FT
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
(Capacity in cubic feet per hour)
Pipe Size (inches)
Length
3/4 1
10
273 514
20
188 353
30 151 284
40 129 243
50 114 215
60 104 195
70 95 179
80 89 167
90
83 157
100
79 148
125
70 131
150 63 119
175 58 109
200 54 102
Refer to current National Fuel Gas Code, NFPA 54.
Gas Input of
)
3
1 1/4 1 1/2
1060 1580
726 1090
583 873
499 747
442 662
400 600
368 552
343 514
322 482
304 455
269 403
244 366
224 336
209 313
INSTALLATION INSTRUCTIONS
2. Use the table for your gas type to find the pipe
size required for your cubic feet per hour of gas
and your pipe length.
Example: The heating value of propane gas for
your location is 2500 BTU/FT
of the tankless water heater is 199,900 BTU/
HR. Additional appliances at the location require
75,000 BTU/HR. Therefore, the cubic feet per
hour = (199,900 + 75,000)/2500 = 109 FT
If the pipe length is 100 ft., then the 3/4-inch
pipe size capable of supplying 197 FT
propane gas will be adequate.
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 cubic feet 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
125
89 185
150
84 175
175
74 155
200 67 140
. The gas input
3
/HR.
3
/HR of
3
1 1 1/4
1150 2350
787 1620
632 1300
541 1110
480 985
434 892
400 821
372 763
349 716
330 677
292 600
265 543
53