MACH
®
Gas Fired Boiler
22
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 rain cap of
any type.
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 total
pressure drop can be distributed over the intake or exhaust as needed for the installation
3.5.5.1
Intake Duct Materials and Sizes
Table 3.5 Air Requirements – SCFM
The air intake duct can be fabricated from PVC, CPVC, single wall
galvanized steel, or other suitable materials. The duct must be
rigid enough to maintain the full required cross sectional area
under all operating conditions. Proper sealing of the intake
ductwork is necessary to prevent infiltration of air from conditioned
space. Joints in PVC or CPVC must be cemented. For
galvanized duct, wrap each joint and seam with adhesive
aluminum tape or other sealant. Connect the air supply duct to the
inlet air collar on the boiler. Fasten the duct to the collar with sheet metal screws and seal with aluminum tape or
sealant. The installation of a bird screen on the intake termination is recommended. Ensure that the screen does not
become blocked with snow, ice, insects etc.
MACH
®
Boiler
MODEL
Required SCFM
C750
175
C900
210
C1050
245