Rinnai RL75I, RL94I installation manual Pipe Sizing Procedure Example

Gas Piping

Pipe Sizing Procedure - Example

The gas supply must be capable of handling the entire gas load 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 in the United States, refer to the National Fuel Gas Code, NFPA 54. For Canadian gas pipe sizing, refer to the Natural Gas and Propane Installation Code CAN/CSA B149.1. The below information is provided as an example. The appropriate table from the applicable code must be used.

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.

Gas Input of all gas products (BTU / HR)

Cubic Feet per Hour (CFH) =

Heating Value of Gas (BTU / FT 3 )

2.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.

Example: The heating value of natural gas for your location is 1000 BTU/FT3. The gas input of the RL94i is 199,000 BTU/HR. Additional appliances at the location require 65,000 BTU/hr. Therefore the cubic feet per hour = (199,000 + 65,000) / 1000 = 264 FT3/HR. If the pipe length is 10 feet then the 3/4 inch pipe size is capable of supplying 264 FT3/HR of natural gas.

Length		Pipe Size (inches)
	3/4	1	1 1/4	1 1/2
10	273	514	1060	1580
20	188	353	726	1090
30	151	284	583	873
40	129	243	499	747
50	114	215	442	662
60	104	195	400	600
70	95	179	368	552
80	89	167	343	514
90	83	157	322	482
100	79	148	304	455
125	70	131	269	403
150	63	119	244	366
175	58	109	224	336
200	54	102	209	313

Length		Pipe Size (inches)
	1/2	3/4	1	1 1/4
10	291	608	1150	2350
20	200	418	787	1620
30	160	336	632	1300
40	137	287	541	1110
50	122	255	480	985
60	110	231	434	892
80	101	212	400	821
100	94	197	372	763
125	89	185	349	716
150	84	175	330	677
175	74	155	292	600
200	67	140	265	543

VB Series Indoor LS Manual 19