Lennox International Inc Merit Series Gas Furnace installation instructions Gas Piping

Gas Piping									4 −	The piping should be sloped 1/4 inch (6.4 mm) per 15
										feet (4.57 m) upward toward the meter from the fur-
Gas supply piping should not allow more than 0.5"W.C. drop
										nace. The piping must be supported at proper intervals
in pressure between gas meter and unit. Supply gas pipe
										[every 8 to 10 feet (2.44 to 3.01 m)] with suitable hang-
must not be smaller than unit gas connection.
										ers or straps. Install a drip leg in vertical pipe runs to the
										unit.
		CAUTION
									5 −	A 1/8" N.P.T. plugged tap or pressure post						is located
										on the gas valve to facilitate test gauge connection.
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe										See figure 35.
shall be installed at the gas valve and extend outside									6 − In some localities, codes may require the installation of
the furnace cabinet. The flexible connector can then
										a manual main shut-off valve and union (furnished by
be added between the black iron pipe and the gas
supply line.										the installer) external to the unit. The union must be of
										the ground joint type.
Gas Supply
1 − This unit is shipped standard for left or right side instal-
												IMPORTANT
	lation of gas piping (or top entry in horizontal applica-
	tions). Connect the gas supply to the piping assembly.
2 −	When connecting the gas supply piping, consider fac-								Compounds used on threaded joints of gas piping
	tors such as length of run, number of fittings, and fur-								must be resistant to the actions of liquified petro-
									leum gases.
	nace rating to avoid excessive pressure drop. Table 9
	lists recommended pipe sizes for typical applications.
3 −	The gas piping must not run in or through air ducts,								NOTE − If emergency shutoff is necessary, shut off the main
	clothes chutes, gas vents or chimneys, dumb waiters,								manual gas valve and disconnect main power to the fur-
	or elevator shafts.								nace. The installer should properly label these devices.
						TABLE 9
					Gas Pipe Capacity − ft3/hr (m3/hr)
Nominal		Internal					Length of Pipe − feet (m)
Iron Pipe
		Diameter
	Size
		inches	10	20	30	40		50			60		70	80	90	100
inches
		(mm)	(3.048)	(6.096)	(9.144)	(12.192)		(15.240)			(18.288)		(21.336)	(24.384)	(27.432)	(30.480)
	(mm)
	1/2	.622	172	118	95	81		72			65		60	56	52	50
	(12.7)	(17.799)	(4.87)	(3.34)	(2.69)	(2.29)		(2.03)			(1.84)		(1.69)	(1.58)	(1.47)	(1.42)
	3/4	.824	360	247	199	170		151			137		126	117	110	104
(19.05)		(20.930)	(10.19)	(7.00)	(5.63)	(4.81)		(4.28)			(3.87)		(3.56)	(3.31)	(3.11)	(2.94)
	1	1.049	678	466	374	320		284			257		237	220	207	195
	(25.4)	(26.645)	(19.19)	(13.19)	(10.59)	(9.06)		(8.04)			(7.27)		(6.71)	(6.23)	(5.86)	(5.52)
	1−1/4	1.380	1350	957	768	657		583			528		486	452	424	400
(31.75)		(35.052)	(38.22)	(27.09)	(22.25)	(18.60)		(16.50)			(14.95)		(13.76)	(12.79)	(12.00)	(11.33)
	1−1/2	1.610	2090	1430	1150	985		873			791		728	677	635	600
	(38.1)	(40.894)	(59.18)	(40.49)	(32.56)	(27.89)		(24.72)			(22.39)		(20.61)	(19.17)	(17.98)	(17.00)
	2	2.067	4020	2760	2220	1900		1680			1520		1400	1300	1220	1160
	(50.8)	(52.502)	(113.83)	(78.15)	(62.86)	(53.80)		(47.57)			(43.04)		(39.64)	(36.81)	(34.55)	(32.844)
	2−1/2	2.469	6400	4400	3530	3020		2680			2480		2230	2080	1950	1840
	(63.5)	(67.713)	(181.22)	(124.59)	(99.95)	(85.51)		(75.88)			(70.22)		(63.14)	(58.89)	(55.22)	(52.10)
	3	3.068	11300	7780	6250	5350		4740			4290		3950	3670	3450	3260
	(76.2)	(77.927)	(319.98)	(220.30)	(176.98)	(151.49)		(134.22)			(121.47)		(111.85)	(103.92)	(97.69)	(92.31)

NOTE − Capacity given in cubic feet (m3 ) of gas per hour and based on 0.60 specific gravity gas.

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