34
Vertical Direct Venting System
Installation
These installations utilize the boiler mounted blower to
draw combustion air from outdoors and uses the natu-
ral buoyancy of the heated flue products to create a
thermal driving head that expels the exhaust gases
from the flue. The negative draft must be within the
range of -0.01 in. to -0.08 in. WC to ensure proper
operation.
The vent material must be in accordance with the
above instructions 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.) and
CSA 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 CSA
B149 Installation Code (Canada). The flue pipe diam-
eter for conventional negative draft venting using
double-wall B type vent is 12” for the ADB 1501.
The connection from the appliance vent to the stack
must be as direct as possible and should be the same
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 sup-
ported for the design and weight of the material
employed to maintain clearances and to prevent phys-
ical damage or separation of joints.
Vertical Direct 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 within 10 feet. The vent cap
should have a minimum clearance of four (4) feet hor-
izontally from and in no case above or below (unless a
four (4) foot horizontal distance is maintained) 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 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 withstand snow
and wind loads.
The vertical direct vent cap is designed for roof top
mounting only. The air inlet opening MUST be installed
one (1) foot above the roof line or above normal snow
levels that might obstruct combustion air flow. This
dimension is critical to the correct operation of the boil-
er and venting system and reduces the chance of
blockage from snow. The vent cap must have a mini-
mum 3 foot vertical clearance above the air inlet
opening.
Fig. 25: Vertical Venting with Add-on Condensing Heat
Exchanger (Category IV) Domestic Water
Summary of Contents for 751
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Page 15: ...15 Fig 6 Dual Boiler Piping Fig 7 Dual Boiler Piping with CHX...
Page 20: ...20 Fig 13 Single Boiler Pool Application Fig 14 Single Boiler Pool Application with CHX...
