Natural Gas - Rinnai SENSEI RX199i Installation And Operation Manual

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, refer to the National Fuel Gas
Code, ANSI Z223.1/NFPA 54, or the Natural
Gas and Propane Installation Code, CSA
B149.1
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.
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.
The information below is provided as an
example. The appropriate table from the
applicable code must be used.

Natural Gas

Table 24: Pressure Drop 0.5 in. wc
Information in table
obtained from NFPA
54, ANSI Z223.1 -
2021.
Specific Gravity:
1/2
Length in ft
Capacity in Cubic Feet of Gas per Hour
(meters)
10 (3) 172
20 (6) 118
30 (9) 95
40 (12) 81
50 (15) 72
60 (18) 65
70 (21) 60
80 (24) 56
90 (27) 52
100 (30) 50
Rinnai Tankless Water Heater Installation and Operation Manual
Schedule 40 Metallic Pipe
Inlet Pressure: Less than 2 psi
0.60
Nominal Pipe Size (in.)
3/4 1
360 678
247 466
199 374
170 320
151 284
137 257
126 237
117 220
110 207
104 195
Table 23: Gas Pipe Sizing Calculation Worksheet
Instructions: Enter values in empty boxes.
Rinnai Mode Gas Input:
A
Additional Appliance Total Gas Input:
B
Heating Value of Gas:
C
Cubic Feet Per Hour (CFH):
(CFH) =
(CFH) =
(CFH) =
Answer:
Rinnai Model Gas Input:
199,000
A
Additional Appliance Total Gas Input:
65,000
B
1 1/4
Heating Value of Gas:
1,000
C
1,390
957
Cubic Feet Per Hour (CFH):
768
(CFH) =
657
(CFH) =
583
528
Answer
An
486
(CFH) =
452
For this example, the pipe diameter must
424
be at least 3/4 in. pipe size and 10 ft (3 m)
in length.
400
Btu/hr
Btu/hr
3
Btu/ft
A + B
C
ft /hr
3
Example
Btu/hr
Btu/hr
Btu/ft
3
A + B
C
199,000+65,000
1,000
264
ft /hr
3
53