Venting For Multiple Boilers; Sealed Combustion/Direct Vent Systems - Harsco Industrial SC-1500 Owner's Manual

3.4.1 Venting for Multiple Boilers

While the vent design parameters outlined in
still apply, achieving those same parameters in a combined vent system, adds a significant degree of
complexity. Therefore, venting systems for multiple boilers shall be designed by experienced and
knowledgeable venting professionals. The venting system shall be designed to prevent backflow of exhaust
gas through idle boilers. For combined breeching installations, please follow recommendations of a qualified
venting engineer/manufacturer.
Harsco Industrial, Patterson-Kelley recommends that common venting systems be
designed for a maximum continuous exhaust pressure of -0.04"
in the common vent. Locking inline dampers are recommended on the discharge of
each boiler in order to maintain a slightly positive exhaust pressure within the boiler
and upstream of the damper. The -0.04"
the exhaust gases from an online boiler does not backflow through offline boiler(s). In
addition, Harsco Industrial, Patterson-Kelley also recommends the use of motorized
dampers in the combustion air intake duct to help prevent the backflow of flue gases
from online boilers through offline boilers.

3.4.2 Sealed Combustion/Direct Vent Systems

These 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.
Drains have been omitted for clarity
above the air intake. The air intake and exhaust vent must extend 6" to 12" from the
exterior wall and be offset. The inlet air duct loss should not exceed 0.22"
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 exhaust duct friction loss. If the air inlet and the exhaust vent
terminate on the same wall of the building they must utilize the same type of termination fitting. Allowable
termination fittings are either 90° elbows or tees. This boiler may be installed with sidewall vent using room air,
see Section 3.3.1 Air Inlet
Section 3.3 Combustion Air
RECOMMENDATION!
Requirements.
P-K SONIC
T T T T echnical Service 1.877.728.5351 echnical Service 1.877.728.5351 echnical Service 1.877.728.5351 echnical Service 1.877.728.5351
in the common flue will help make sure
W.C.
NOTE
The exhaust vent must be at least 3 feet
.
36"
Minimum
12" Minimum
TM
Gas Fired Boiler
and Section 3.4 Vent Termination
when measured
W.C.
W.C.