Raypak HD401, HD101 Barometric Damper, Support of Vent Stack, Vent Terminal Location

Combustion Air	Exhaust	Venting Category	Certified	Combustion Air
Supply	Configuration		Appliance Material	Inlet Material
	Vertical Natural	I	Type B or any
From Inside			Category I Venting
	Draft Venting		System*
Building (Non-Direct
Venting)	Horizontal	III	Stainless Steel
	Thru-wall
	Venting		(Gas Tight)
	Vertical Venting	I	Type B or any
			Category I Venting	Galvanized Steel
From Outside			System*
				PVC
Building (Direct				ABS
	Horizontal	III	Stainless Steel
Venting)	Thru-wall			CPVC
	Venting		(Gas Tight)
*As defined in the latest edition of the NFGC, or in Canada, the B149.
	Table I: Venting Category Requirements

Barometric Damper

A barometric damper may be required when vent heights exceed 25 feet or when the draft is greater than -0.08 in. WC. In these installations, a barometric damper (single acting) is required.

The damper should be installed NO CLOSER than 18 in. from the discharge of the unit and no closer than 18 in. from a combustible ceiling. The damper can be installed in horizontal or vertical runs of vent pipe as necessary. Installation in a bull-head tee is acceptable as shown in the NFGC.

The weights on the damper should be adjusted per the damper manufacturer’s instructions for proper opera- tion, to maintain –0.01 to –0.08 in. WC, 12 in. from the heater outlet, at all firing conditions.

Support of Vent Stack

The weight of the vent stack or chimney must not rest on the heater vent connection. Support must be pro- vided in compliance with applicable codes. The vent should also be supported to maintain proper clear- ances from combustible materials.

Use insulated vent pipe spacers where the vent pass- es through combustible roofs and walls.

Vent Terminal Location

NOTE: During winter months check the vent cap and make sure no blockage occurs from build up of snow.

1.Condensate can freeze on the vent cap. Frozen condensate on the vent cap can result in a blocked flue condition.

2.Give special attention to the location of the vent termination to avoid possibility of property damage or personal injury.

3.Gases may form a white vapor plume in winter. The plume could obstruct a window view if the ter- mination is installed in close proximity to windows.

4.Prevailing winds, in combination with below freez- ing temperatures, can cause freezing of condensate and water/ice build-up on buildings, plants or roofs.

5.The bottom of the vent terminal and the air intake shall be located at least 12 in. above grade, includ- ing normal snow line.

6.Un-insulated single-wall metal vent pipe shall not be used outdoors on cold climates for venting gas utilization equipment.

7.Through-the-wall vents for Category II and IV appliances and non-categorized condensing appli-

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