Rinnai ThermaCirc360 RUR199i Installation And Operation Manual page 47

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
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: 0.60
Nominal Pipe Size (in.)
1/2 3/4
Capacity in Cubic Feet of Gas per Hour
172 360
118 247
95 199
81 170
72 151
65 137
60 126
56 117
52 110
50 104
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:
Less than 2 psi
1 1 1/4
678 1,390
466 957
374 768
320 657
284 583
257 528
237 486
220 452
207 424
195 400
A BTU/HR
B BTU/HR
C BTU/FT
A +
(CFH) =
C
(CFH) =
=
FT
CFH
EXAMPLE
Rinnai Model Gas Input:
199,000
A BTU/HR
Additional Appliance Total Gas
Input:
65,000
B BTU/HR
Heating Value of Gas:
1,000
C BTU/FT
Cubic Feet Per Hour (CFH):
A +
(CFH) =
C
199,000+65,000
(CFH) =
1000
ANSWER:
= 264
FT
CFH
For this example, the pipe
diameter must be at least 3/4 in.
pipe size and 10 ft (3 m) in
length.
3
B
3
/HR
3
B
3
/HR
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