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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. The exhaust vent must be at least 3 feet 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
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 3.4.1.
Inlet Duct Connection to Boiler
Connect the air supply duct to the inlet air collar on the boiler. The air inlet collar is 11.875" OD. Fasten
the air inlet duct to the collar with sheet metal screws at 90° angles and seal with aluminum tape or
sealant.
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. The installation of a birdscreen on the
intake termination is recommended. Ensure that the screen does not become blocked with snow, ice,
insects, etc.
Category II Installations
The SONIC boilers are dual-certified for either Category II or Category IV operation. Category II
appliances operate with a non-positive vent static pressure and with a vent temperature that may cause
excessive condensate production in the vent. There are several requirements for reliable operation of
the boilers under Category II conditions:
Revised: June 2, 2017
Released: June 2, 2017
NOTE
duct loss should not exceed 0.22" W.C
HARSCO Industrial, Patterson-Kelley 2017
All Rights Reserved.
P-K SONIC
Technical Service 1.877.728.5351
.
36"
Minimum
12" Minimum
1004905978 P-K SONIC NURO Installation and
Owners Manual (Rev F Jun-2017).docx
®
Gas Fired Boiler
Page 30
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