Table of Contents
Advertisement
Natural Draft Vertical Venting
System Installation
Natural draft venting uses the natural buoyancy of the
heated flue products to create a thermal driving head
that expels the exhaust gases from the flue. The neg-
ative draft must be within the range of 0.01 in. to 0.08
in. WC negative to ensure proper operation. The vent
material must be in accordance with the above instruc-
tions for vent materials. Vent material must be listed by
a nationally recognized test agency.
The maximum and minimum venting length for
Category I appliance shall be determined per the lat-
est edition of the National Fuel Gas Code (U.S.) or
B149 Installation Code (Canada).
The diameter of vent flue pipe should be sized accord-
ing to Part 11 of the latest edition of the National Fuel
Gas Code (U.S.) and part 7 and appendix B of the
CSA B149 Installation Code (Canada). The flue pipe
diameter for conventional negative draft venting using
double-wall B type vent is 8" for the ADB 751, 10" for
the 1001, and 12" for the ADB 1501.
NOTE: Vent Adapter will have to be used to connect
B vent to the unit.
The connection from the appliance vent to the stack
must be as direct as possible and shall be the same
diameter as, or larger than the vent outlet. The vent
must be installed to prevent accumulation of
condensate and, where necessary, have means
provided for drainage of condensate. The horizontal
breaching of a vent must have an upward slope of not
less than 1/4 inch per linear foot from the boiler to the
vent terminal. The horizontal portions of the vent shall
also be supported for the design and weight of the
material employed to maintain clearances and to
prevent physical damage or separation of joints.
Natural Draft Vertical Vent
Termination
The vent terminal should be vertical and should termi-
nate outside the building at least two (2) feet above the
highest point of the roof that is within 10 feet. The vent
cap should have a minimum clearance of four (4) feet
horizontally from and in no case above or below
(unless a four (4) foot horizontal distance is main-
tained) electric meters, gas meters, regulators and
relief equipment.
The distance of the vent terminal from adjacent public
walkways, adjacent buildings, open windows and
building openings must be consistent with the National
Fuel Gas Code, or in Canada, the latest edition of the
CSA B149 Installation Code for Gas Burning
Appliances and Equipment. Gas vents supported only
by flashing and extended above the roof more than
five feet should be securely guyed or braced to with-
stand snow and wind loads.
CAUTION: Listed vent cap terminal must be used
and sized adequately to evacuate the flue products
from the boilers.
Natural Draft Vertical Venting with
Common Venting System, Category
I Appliance Only
(NOT to be Utilized with Add-on
Condensing Heat Exchanger)
Manifolds that connect more than one boiler to a com-
mon chimney must be sized to handle the combined
load. Consult available guides for proper sizing of the
manifold and the chimney. At no time should the area
of the vent be less than the area of the largest boiler
exhaust outlet.
WARNING: Vent connectors serving appliances
vented by natural draft shall not be connected into
any portion of mechanical draft systems operating
under a positive pressure.
CAUTION: Vent connectors for natural draft
venting systems must be type "B" vent or better.
Common venting systems may be too large when an
existing unit is removed. At the time of removal of an
existing appliance, the following steps must be fol-
lowed with each appliance remaining connected to the
common venting system placed in operation, while the
other appliances remaining connected to the common
venting system are not in operation.
a) Seal any unused opening in the common venting
system.
b) Visually inspect the venting system for proper size
and horizontal pitch and determine there is no
blockage or restriction, leakage, corrosion or other
unsafe condition.
c) Insofar as is practical, close all building doors and
windows and all doors between the space in which
the appliances remaining connected to the com-
mon venting system are located and other spaces
of the building. Turn on clothes dryers and any
29
Advertisement
Table of Contents
