Lochinvar 399 Continued, Vertical Rooftop Air Inlet, Air Inlet Cap for Sidewall Termination

Hydronic Heating Boilers and Domestic Water Heaters

INSTALLATION	Continued	You must install the combustion air inlet cap and the powered
		vent cap on the same wall and in the same pressure zone.
		Do not install the combustion air inlet cap closer than 10 feet
		(3.05m) from an inside corner of an L-shaped structure.
		Vertical Rooftop Air Inlet
		Use the vertical air inlet terminations available from the
		appliance manufacturer, recommended and/or supplied by the
		vent manufacturer, or use two 90° elbows as described on
		page 24.

FIG. 15 Air Inlet Cap for Sidewall Termination

To prevent recirculation of flue products from an adjacent vent cap into the combustion air inlet, follow all applicable clearance requirements in the latest edition of the National Fuel Gas Code and/or CAN/CGA-B149 Installation Code and instructions in the Installation and Service Manual.

You must install the combustion air inlet cap at least one foot (0.30m) above ground level and above normal snow levels.

The point of termination for the combustion air inlet cap must be at least 3 feet (0.91m) below the point of flue gas termination (powered vent cap) if it is located within 10 feet (3.05m) of the flue outlet from the powered vent cap. Make sure to properly install the air inlet cap assembly on the air inlet pipe.

3'

12"

FIG. 16 Roof Top Combustion Air Inlet

Clearances

You must locate the air inlet termination elbow at least 12" (30cm) above the roof or above normal snow levels.

TABLE–C

Minimum Recommended Combustion Air Supply To Boiler Room

		Combustion Air Source
Boiler Input	Outside Air*/2 Openings		Outside Air*/1 Opening		Inside Air/2 Openings
399,999	100 in2 (745 cm2)		133 in2 (858 cm2)		400 in2		(2581 cm2)
500,000	125 in2 (806 cm2)		167 in2 (1077 cm2)		500 in2		(3226 cm2)
650,000	163 in2 (1052 cm2)		217 in2 (1400 cm2)		650 in2		(4194 cm2)
750,000	188 in2 (1213 cm2)		250 in2 (1613 cm2)		750 in2		(4839 cm2)
990,000	248 in2 (1,600cm2)		330 in2 (2,129 cm2)		990 in2		(6,388 cm2)
1,260,000	315 in2	(2,032cm2)	420 in2	(2,710 cm2)	1260 in2		(8,130 cm2)
1,440,000	360 in2	(2,323cm2)	480 in2	(3,097 cm2)	1440 in2		(9,291 cm2)
1,800,000	450 in2	(2,903cm2)	600 in2	(3,871 cm2)	1800 in2 (11,614 cm2)
2,070,000	518 in2	(3,342cm2)	690 in2	(4,452 cm2)	2070 in2	(13,356 cm2)

*Outside air openings shall directly communicate with the outdoors. When combustion air is drawn from the outside through a duct, the net free area of each of the two openings must have twice (2 times) the free area required for Outside Air/2 Openings. The above requirements are for the boiler only, additional gas fired units in the boiler room will require an increase in the net free area to supply adequate combustion air for all units. Combustion air requirements are based on the latest edition of the National Fuel Gas Code, ANSI Z223.1, in Canada refer to CAN/CGA-B149 Installation Code. Check all local code requirements for combustion air.

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