Installation Guide

Rinnai Tankless Water Heater Installation and Operation Manual 55
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.
A
Btu/hr
B Btu/hr
Table 23: Gas Pipe Sizing Calculation Worksheet
Instructions: Enter values in empty boxes.
Rinnai Mode Gas Input:
Additional Appliance Total Gas Input:
Answer:
Heating Value of Gas:
A + B
(CFH) =
C
(CFH) =
(CFH) =
ft3 /hr
Cubic Feet Per Hour (CFH):
Natural Gas
Table 24: Pressure Drop 0.5 in. wc
Example
Rinnai Model Gas Input:
A 199,000 Btu/hr
Addional Appliance Total Gas Input:
B 65,000 Btu/hr
Heang Value of Gas:
C 1,000 Btu/ft3
Cubic Feet Per Hour (CFH):
A + B
Information in table
obtained from NFPA
54, ANSI Z223.1 -
2021.
Schedule 40 Metallic Pipe
Inlet Pressure: Less than 2 psi
Specific Gravity: 0.60
Nominal Pipe Size (in.)
1/2 3/4 1 1 1/4
Length in ft
(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
(CFH) =
C
40 (12) 81 170 320 657
199,000+65,000
50 (15) 72 151 284 583
(CFH) =
1,000
60 (18) 65 137 257 528
70 (21) 60 126 237 486
An
(CFH) =
264
3/hr
80 (24) 56 117 220 452
For this example, the pipe diameter must
be at least 3/4 in. pipe size and 10 ft (3 m)
in length.
90 (27) 52 110 207 424
100 (30) 50 104 195 400
Answer
C Btu/ft
3