Lenox Official Manual for Gas Furnace - Performance and Installation Guidelines

TABLE 5

Vent Connector Capacity

Type B Double−Wall Vents with Type B Double−Wall Connectors

Serving Two or More Category I Appliances

Vent	Connector				Vent and Connector Diameter − D (inches)
Height	Rise		3 Inch			4 Inch			5 Inch			6 Inch
H	R				Appliance Input Rating in Thousands of Btu Per Hour
(feet)	(feet)
		MIN		MAX	MIN		MAX	MIN		MAX	MIN		MAX
	1	22		37	35		66	46		106	58		164
6	2	23		41	37		75	48		121	60		183
	3	24		44	38		81	49		132	62		199
	1	22		40	35		72	49		114	64		176
8	2	23		44	36		80	51		128	66		195
	3	24		47	37		87	53		139	67		210
	1	22		43	34		78	49		123	65		189
10	2	23		47	36		86	51		136	67		206
	3	24		50	37		92	52		146	69		220
	1	21		50	33		89	47		142	64		220
15	2	22		53	35		96	49		153	66		235
	3	24		55	36		102	51		163	68		248
	1	21		54	33		99	46		157	62		246
20	2	22		57	34		105	48		167	64		259
	3	23		60	35		110	50		176	66		271
	1	20		62	31		113	45		181	60		288
30	2	21		64	33		118	47		190	62		299
	3	22		66	34		123	48		198	64		309

TABLE 6

Common Vent Capacity

Type B Double−Wall Vents with Type B Double−Wall Connectors

Serving Two or More Category I Appliances

Vent				Common Vent Diameter − D (inches)
Height	4 Inch		5 Inch			6 Inch		7 Inch
H			Appliance Input Rating in Thousands of Btu Per Hour
(feet)
	FAN + FAN	FAN + NAT	FAN + FAN		FAN + NAT	FAN + FAN	FAN + NAT	FAN + FAN	FAN + NAT
6	92	81	140		116	204	161	309	248
8	101	90	155		129	224	178	339	275
10	110	97	169		141	243	194	367	299
15	125	112	195		164	283	228	427	352
20	136	123	215		183	314	255	475	394
30	152	138	244		210	361	297	547	459

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