Chapter 3 — Stack and Intake Vent Sizing and Installation
3-6 Part No. 750-263
B.HORIZONTAL THRU-WALL VENTING / INSIDE
COMBUSTION AIR
(CATEGORY III & IV)
1. Installation
For boilers connected to gas vents or chimneys, vent installations
shall be in accordance with Part 7, Venting of Equipment, of the
latest edition of National Fuel Gas Code, or in Canada, the latest
edition of CAN/CSA-B 149.1 and.2 Installation Code for Gas
Burning Appliances and Equipment, or applicable provisions of
local building codes.
These installations utilize the boiler-mounted blower to vent the
combustion products to the outside. Combustion air is taken from
inside the room and the vent is installed horizontally through the
wall to the outside. Adequate combustion and ventilation air must
be supplied to the boiler room in accordance with the National Fuel
Gas Code or, in Canada, the latest edition of CAN/CSA-B 149.1 and
.2 Installation Code for Gas Burning Appliances and Equipment.
The direct vent cap is not considered in the overall length of the
venting system.
The vent must be installed to prevent flue gas leakage. Care must
be taken during assembly to insure that all joints are sealed properly
and are airtight.
The vent must be installed to prevent the potential accumulation of
condensate in the vent pipes. It is recommended that:
1. The vent be installed with a slight downward slope of not more
than 1/4" per foot of horizontal run to the vent terminal.
2. The vent be insulated through the length of the horizontal run.
For appliances installed in extreme cold climate, it is recommended
that:
1. The vent be installed with a slight upward slope of not more than
1/4" per foot of horizontal run to the vent terminal. In this case,
an approved condensate trap must be installed per applicable
codes.
2. The vent be insulated through the length of the horizontal run.
2. Horizontal Thru-Wall Stack Vent Termination
The stack vent cap MUST be mounted on the exterior of the
building. The stack vent cap cannot be installed in a well or below
grade. The stack vent cap must be installed at least one (l) foot
above ground level and above normal snow levels.
No substitutions of flue pipe or vent cap material are allowed. Such
substitutions would jeopardize the safety and health of inhabitants.
The stainless steel direct vent cap must be furnished in accordance
with AGA/ CSA requirements.
Figure 3-3 Horizontal Venting
Thru-Wall Using Inside Air For
Combustion
24" Minimum
Flue Gas Vent
Inside Air
Combustion
Intake
(w/Screen)
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