Installation Sheet

Rinnai Tankless Water Heater Installaon and Operaon Manual 51
The gas supply must be capable of handling the enre gas load
required at the locaon. 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 Naonal Fuel Gas Code,
ANSI Z223.1/NFPA 54, or the Natural Gas and Propane Installaon
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 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.
Use the table for your gas type and pipe type to nd 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 informaon below is provided as an example. The appropriate
table from the applicable code must be used.
Schedule 40 Metallic Pipe
Inlet Pressure: Less than 2 psi
Specic Gravity: 0.60
Gas Pipe Sizing Reference Tables
Informaon in table obtained from
NFPA 54, ANSI Z223.1 - 2015.
Pressure Drop 0.5 in. w.c.
Nominal Pipe Size (in.)
1/2 3/4 1 1 1/4
Length in  (meters) Capacity in Cubic Feet of Gas per Hour
10 (3) 172 360 678 1,390
20 (6) 118 247 466 957
30 (9) 95 199 374 768
40 (12) 81 170 320 657
50 (15) 72 151 284 583
60 (18) 65 137 257 528
70 (21) 60 126 237 486
80 (24) 56 117 220 452
90 (27) 52 110 207 424
100 (30) 50 104 195 400
Natural Gas
EXAMPLE
Rinnai Model Gas Input:
Addional Appliance Total Gas
Input:
Heang Value of Gas:
Cubic Feet Per Hour (CFH):
ANSWER:
B
65,000
BTU/HR
C
1,000
BTU/FT
3
A
199,000
BTU/HR
199,000+65,000
(CFH) =
1000
264
FT
3
/HR
CFH =
For this example, the pipe
diameter must be at least 3/4 in.
pipe size and 10  (3 m) in
length.
A + B
(CFH) =
C
Instrucons: Enter values in empty boxes.
Rinnai Model Gas Input:
Addional Appliance Total Gas Input:
Heang Value of Gas:
Cubic Feet Per Hour (CFH):
ANSWER:
B BTU/HR
C BTU/FT
3
A BTU/HR
(CFH) =
FT
3
/HR
CFH =
A + B
(CFH) =
C
GAS PIPE SIZING CALCULATION WORKSHEET