68 Venting for Combustion Air
5.3 Selecting a Vent Type
All Navien boilers are Category IV appliances and prepared at the factory to be direct vented (sealed
combustion). Navien recommends direct air vent installations whenever possible to avoid back drafting cold air
through the boiler unit. If you cannot use a direct vent, ensure that an ample supply of make-up air is available in
the installation location.
Navien also recommends installing a new vent system with this appliance. If reusing an existing vent system,
thoroughly inspect it for punctures, cracks, or blockages prior to connecting it to the boiler.
Direct Venting
The boiler uses a 2 in or 3 in diameter exhaust and a 2 in or 3 in diameter air intake ducts. To ensure the draw of
air directly from and exhaust of air directly to the outside of the building, create an airtight seal from the boiler
collar to the vent termination.
Intake materials can be made of ABS, PVC, CPVC, PP, galvanized or stainless steel, corrugated aluminum or
any other such materials. If you use a corrugated material, ensure that there is not inadvertent crimping of, or
damage to, the intake air pipe.
When using direct venting, maintain the following venting clearances, as required by
ANSI Z21.10.3 and the
National Fuel Gas Code, ANSI Z223.1/NFPA 54, and CAN/CGA B149.1 Natural Gas and Propane Installation
Code:
Ref Description
Canadian Direct Vent
Installations
1
US Direct Vent
Installations
2
A
Clearance above grade, veranda, porch, deck,
or balcony
12 in (30 cm)
12 in (30 cm)
B
Clearance to window or door that may be
opened
36 in (91 cm)
12 in (30 cm)
C
Clearance to permanently closed window
*
*
Summary of Contents for NFC-250/175H
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