Raypak 122, Installation & Operating Instructions Manual

22

Table H:  Venting Category Requirements

Combustion Air

Supply

Exhaust

Configuration

Venting Category

Certified

Appliance Material

Combustion Air

Inlet Material

From 

Inside

Building (Non-Direct

Venting)

Vertical

Natural

Draft Venting

I

Type B or and

Category I Venting

System*

Horizontal

Thru-wall

Venting

III

Stainless Steel

(Gas Tight)

From 

Outside

Building (Direct

Venting)

Vertical

Venting

I

Type B or and

Category I Venting

System*

Galvanized Steel

PVC

ABS

CPVC

Horizontal

Thru-wall

Venting

III

Stainless Steel

(Gas Tight)

*As defined in the latest edition of the NFGC, or in Canada, the B149.

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 recommended.

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.

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

General

Give special attention to the location of the vent termi-
nation to avoid possibility of property damage or
personal injury.

a)  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.

b)  Prevailing winds could cause freezing of conden-

sate and water/ice build-up on building, plants or
roof.

c)  The bottom of the vent terminal and the air intake

shall be located at least 12 in. above grade.

d)  Un-insulated single-wall metal vent pipe shall not

be used outdoors on cold climates for venting gas
utilization equipment.

e)  Through-the-wall vents for Category II and IV

appliances and non-categorized condensing appli-
ances shall not terminate over public walkways or

NOTE:

During winter months check the vent cap

and make sure no blockage occurs from build up of
snow. Condensate can freeze on the vent cap.
Frozen condensate on the vent cap can result in a
blocked flue condition.