Harsco Industrial MACH C1500GG Installation & Owner's Manual page 21

3.5.3.6 Vent Terminations
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 at least 3 ft above a forced air inlet located within 10 ft.
3.5.4 Venting for Multiple Boilers
The venting instructions in this manual apply to a single boiler.
Venting systems for multiple boilers must be designed by experienced and knowledgeable
professionals. The venting system must prevent backflow of exhaust gas through idle boilers.
3.5.5
Sealed Combustion/Direct Vent Systems
®
The MACH Boilers are also certified for operation with a sealed combustion air and pressurized venting system.
Such a system employs a sealed combustion air intake duct leading from outdoors and a sealed exhaust vent
terminating outdoors. Air flow through the system is maintained by the combustion air fan. Allowable configurations
of vent and air intake terminations are illustrated below.
The combined pressure drop of the air supply duct and exhaust vent must not exceed 0.44" w.c. This
pressure drop includes both the inlet and vent ducts friction loss. For example, if the inlet air duct loss is -0.2" w.c.,
the vent duct loss cannot exceed 0.24" w.c.
Reference: NFPA 54/ANSI Z223.1 National
Fuel Gas Code
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 can not 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
birdscreen with 1" x 1" openings is
recommended for the termination. Harsco
Industrial, Patterson-Kelley does not
recommend using a vent rain cap of any type.
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MACH® Gas-Fired Boiler