Rinnai Sensei CU199i Installation And Operation Manual page 62

4. 1 0.2 Gas Pipe Sizing Reference Tables
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 26: Pressure Drop 0.5 in. w.c.
Information in table
obtained from NFPA 54,
ANSI Z223.1 - 2015.
Length in ft (meters)
10 (3)
20 (6)
30 (9)
40 (12)
50 (15)
60 (18)
70 (21)
80 (24)
90 (27)
100 (30)
Rinnai Tankless Water Heater Installation and Operation Manual
Schedule 40 Metallic Pipe
Inlet Pressure:
Specific Gravity:
Nominal Pipe Size (in.)
1/2 3/4
Capacity in Cubic Feet of Gas per Hour
172 360 678
118 247 466
95 199 374
81 170 320
72 151 284
65 137 257
60 126 237
56 117 220
52 110 207
50 104 195
Table 25: Gas Pipe Sizing Calculation
Worksheet
Instructions: Enter values in empty boxes.
Rinnai Model Gas Input:
Additional Appliance Total Gas Input:
Heating Value of Gas:
Cubic Feet Per Hour (CFH):
Answer:
Rinnai Model Gas Input:
Less than 2 psi
0.60
Additional Appliance Total Gas Input:
1 1 1/4
Heating Value of Gas:
1,390
Cubic Feet Per Hour (CFH):
957
768
657
583
528
Answer:
486
452
For this example, the pipe diameter
424
must be at least 3/4 in. pipe size and
10 ft (3 m) in length.
400
A
B
C
(CFH) =
(CFH) =
(CFH) =
Table 27: Example
199,000
A
65,000
B
1,000
C
A
(CFH) =
199,000+65,000
(CFH) =
1,000
264
(CFH) =
Btu/hr
Btu/hr
Btu/ft
3
A + B
C
ft /hr
3
Btu/hr
Btu/hr
Btu/ft
3
+ B
C
ft /hr
3
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