Burnham MMII manual Gas Piping, Rated Input

V. Gas Piping

A.Size gas piping. Design system to provide adequate gas supply to boiler. Consider these factors:

1.Allowable pressure drop from point of delivery to boiler. Maximum allowable system pressure is ½ psig. Actual point of delivery pressure may be less; contact gas supplier for additional information. Minimum gas valve inlet pressure is stamped on the rating label located in the boiler's vestibule compartment.

2.Maximum gas demand. Table 2 lists boiler input rate. Also consider existing and expected future gas utilization equipment (i.e. cooking equipment).

3.Length of piping and number of fittings. Refer to Table 3 for maximum capacity of Schedule 40 pipe. Table 4 lists equivalent pipe length for standard fittings.

Table 2: Rated Input

Boiler	Input Rate		Gas
	[cubic feet per hour]
Model			Connection
	Natural
Number		LP Gas	Size (Inches)
	Gas
MMII4-70	70	28	½
MMII4-105	105	42	½
MMII5-105	105	42	½
MMII5-140	140	56	½

4.Specific gravity of gas. Gas piping systems for gas with a specific gravity of 0.70 or less can be sized directly from Table 3, unless authority having jurisdiction specifies a gravity factor be applied. For specific gravity greater than 0.70, apply gravity factor from Table 5. If exact specific gravity is not shown choose next higher value.

For materials or conditions other than those listed above, refer to National Fuel Gas Code, NFPA 54/ ANSI Z223.1, or size system using standard engineering methods acceptable to authority having jurisdiction.

B.Connect boiler gas valve to gas supply system.

1.Use methods and materials in accordance with local plumbing codes and requirements of gas supplier. In absence of such requirements, follow National Fuel Gas Code, ANSI Z223.1.

2.Use thread (joint) compounds (pipe dope) resistant to action of liquefied petroleum gas.

3.Install sediment trap, ground-joint union and manual shut-off valve upstream of boiler gas control valve and outside of jacket. See Figure 8.

4.All above ground gas piping upstream from manual shut-off valve must be electrically continuous and bonded to a grounding electrode. Do not use gas piping as grounding electrode. Refer to National Electrical Code, ANSI/NFPA 70.

Table 3: Maximum Capacity of Schedule 40 Pipe in CFH For Gas Pressures of 0.5 psig or Less

Length		0.3 inch w.c. Pressure Drop					0.5 inch w.c. Pressure Drop
[Feet]	½		¾	1	1¼	½		¾	1	1¼
10	132		278	520	1,050	175		360	680	1,400
20	92		190	350	730	120		250	465	950
30	73		152	285	590	97		200	375	770
40	63		130	245	500	82		170	320	660
50	56		115	215	440	73		151	285	580
60	50		105	195	400	66		138	260	530
70	46		96	180	370	61		125	240	490
80	43		90	170	350	57		118	220	460
90	40		84	160	320	53		110	205	430
100	38		79	150	305	50		103	195	400

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