Harsco Industrial 1004905923, Installation & Owner'S Manual

MODU-FIRE

®

 Forced Draft Gas-Fired Boiler 2500-3000 

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.   

Air Requirements – SCFM 

MFD MODEL 

Required SCFM 

N2500 583 

N3000 700 

Thru the roof

Thru the roof

Thru the Wall

Note:
Elbow and Tee 
May be oriented 
in any direction 

Thru the Wall

Note:
Elbow and Tee 
May be oriented 
in any direction