Harsco Industrial 1004905923 Installation & Owner's Manual page 20

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 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. It is important to locate the
exhaust duct in such a way that it does not become blocked due to snow, ice, and/or other natural or man-made
obstructions.
VERTICAL VENTING
Harsco Industrial, Patterson-Kelley does not recommend the use
of a vent cap. A screen termination is not recommended due to
the possibility of ice formation on the screen. Rain is actually
beneficial to the vent internals.
SIDEWALL VENTING – N2500 & N3000 MFD
Harsco Industrial, Patterson-Kelley requires a "T" or 90
degree elbow to be used on the termination end of
sidewall venting on these models. The venting connection
for this "T" or 90 degree elbow should extend a minimum
of 12" from the wall, in addition to other venting
requirements.
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 MODU-FIRE Forced Draft boilers are also certified for operation with a sealed combustion air and pressur-
ized 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.
Intake Duct Materials and Sizes
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 birdscreen on the intake termi-
nation is recommended. Ensure that the screen does not become blocked with snow, ice, insects etc.
The combined pressure drop of the air supply duct and exhaust
vent must not exceed 1.0" w.c. This combined pressure drop can
be distributed over the intake or exhaust as needed provided that the
air inlet pressure loss does not exceed -0.5" w.c.
®
MODU-FIRE Forced Draft Gas-Fired Boiler 2500-3000
Thru the roof Thru the roof
Thru the Wall Thru the Wall
Note: Note:
Elbow and Tee Elbow and Tee
May be oriented May be oriented
in any direction in any direction
MFD MODEL
20
Air Requirements – SCFM
Required SCFM
N2500 583
N3000 700