Sealed Combustion/Direct Vent Systems; Inlet Duct Connection To Boiler; Intake Duct Materials And Sizes - Patterson-Kelley MACH C-1500H Installation & Owner's Manual

3.5.4 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 by at least 48" as shown. The inlet
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. This boiler may be installed with
sidewall vent using room air. Allowable termination fittings are either 90° elbows or tees. This boiler may
be installed without termination fittings if both the exhaust and air intake are on the same wall of the
building, see Section 3.4.1.

3.5.5 Inlet Duct Connection to Boiler

Connect the air supply duct to the inlet air collar on the boiler. Fasten the air inlet duct to the collar with
sheet metal screws at 90° angles and seal with aluminum tape or sealant.

3.5.6 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 1" x 1" birdscreen
on the intake termination is recommended. Ensure that the screen does not become blocked with
snow, ice, insects, etc.
Revised: January 3, 2020
Released: January 3, 2020
NOTE
air duct loss should not exceed 0.22" W.C
36"
Minimum
12" Minimum
 Patterson-Kelley 2020
All Rights Reserved.
®
P-K MACH
Technical Service 1.877.728.5351
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Exhaust
Vent
1004905981 P-K MACH C1500H-C4000 Installation and
Owners Manual (Rev F Jan-2020).docx
Gas Fired Boiler
Air Inlet
Page 34