Harsco Industrial SC-2000 Installation & Owner's Manual page 25

Gas Fired Boiler
3.5.3.4 Vent Termination
The vent shall extend at least three (3) feet above the roof, or at least two (2) feet above the highest part of any
structure within ten (10) feet of the vent. This is illustrated in the following diagram.
Additionally the boiler vent shall terminate
Figure 3.5.3.4
at least 3 ft above a forced air inlet located
within 10 ft.
To prevent the possible re-circulation of flue
gases, the vent designer must take into
consideration such things as prevailing
winds, eddy zones, building configurations,
etc. Harsco Industrial, Patterson-Kelley
cannot be responsible for the effects
such adverse conditions may have on
the operation of the boilers.
Dimensions listed above are minimums
and may not be sufficient for conditions at
a specific job site.
Vertical vents are allowed to be terminated
with a variety of ends, including plain
straight pipe, elbow or vent tee. Horizontal
vents must be terminated as illustrated in
Section 3.5.5. A bird screen with 1" x 1"
openings is recommended for the
termination. Harsco Industrial, Patterson-
Kelley does not recommend using a vent
Reference: NFPA 54/ANSI Z223.1 National Fuel Gas Code
rain cap of any type.
3.5.4 Venting for Multiple Boilers
While the vent design parameters outlined in Section 3.5.3 still apply, achieving those same parameters in a
combined vent system, adds a significant degree of complexity. Therefore, venting systems for multiple boilers
shall be designed by experienced and knowledgeable venting professionals. The venting system shall be
designed to prevent backflow of exhaust gas through idle boilers. For combined breeching installations, please
follow recommendations of a qualified venting engineer/manufacturer.
Harsco Industrial, Patterson-Kelley recommends that common venting systems be designed for a
maximum continuous exhaust pressure of -0.04" w.c. when measured in the common vent. Locking
inline dampers are recommended on the discharge of each boiler in order to maintain a slightly positive
exhaust pressure within the boiler and upstream of the damper. The -0.04" w.c. in the common flue will
help make sure the exhaust gases from an online boiler does not backflow through offline boiler(s). In
addition, Harsco Industrial, Patterson-Kelley also recommends the use of motorized dampers in the
combustion air intake duct to help prevent the backflow of flue gases from online boilers through offline
boilers.
Harsco Industrial, Patterson-Kelley Technical Service 1.877.728.5351
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