Harsco Industrial C1500H Installation & Owner's Manual page 27

It is recommended that if using common venting the common vent should be designed for maximum
continuous pressure of -.04 with sizing equal throughout the run, and Tee's be used on the outlet of the
boilers with locking dampers on the exhaust directly off the boilers and combustion air dampers on the
combustion air inlets.
Sealed Combustion/Direct Vent Systems - Sealed Combustion Application
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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. One of the allowable configurations of
vent and air intake terminations are illustrated to the right. Note: drains have been omitted for clarity.
NOTICE! Sealed combustion intake and
exhaust can be terminated either vertically
(through the roof) or horizontally (through the
wall). If the exhaust vent is to be run and
terminated horizontally the combustion air
intake must be run and terminated in the same
fashion. See picture to the right.
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.
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The MACH C1500H/C2000H/C2500/C3000/
C4000 boilers are certified for direct sidewall or
roof venting within a sealed combustion.
Both the air inlet and the exhaust vent must
terminate on the same wall or roof of the building
and must utilize the same type of termination
fitting with the same orientation. Allowable
termination fittings are: 90 elbows or tees.
NOTICE! Do not install this boiler with
sidewall vent and room air inlet. Nuisance
Alarms will occur.
The figure above shows the sidewall penetration requirements. The exhaust vent must be at least 3 feet above the air
intake. The air intake and exhaust vent must extend at least 12 inches from the exterior wall. If the vent is terminated
through the roof, the combustion air intake can be supplied from either a vertical or horizontal termination.
3.5.4.1 Inlet Duct Connection to Boiler
Connect the air supply duct to the inlet air collar on the boiler. The combustion air inlet collars sizes fit common sheet
metal duct. Fasten the air inlet duct to the collar with sheet metal screws at 90° angles and seal with aluminum tape
or sealant.
Note: Never shall the combustion air inlet be operated with a positive pressure.
27
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MACH Gas Fired Boiler
36" 36"
12" 12"
Minimum Minimum