66 Installing a Common Vent System
9.1 About the Common Vent System
The Navien Common Vent System* provides an easy way to install
the vent system for up to 8 Navien NFB boiler units. By sharing
the main intake and exhaust vent pipes, effective system venting
is available with less venting materials and minimal number of
penetrations on the walls or roofing.
* Independently tested and approved by CSA
Read all safety messages and carefully follow the guidelines in this
manual when installing a common vent system for the NFB boiler
units.
WARNING
Improper venting of the boiler units can result in excessive
levels of carbon monoxide, which can lead to severe
personal injury or death. The boiler units must be vented
in accordance with the “Venting of Equipment“ section of
the latest edition of the ANSI Z223.1/NFPA 54 Natural Fuel
Gas Code in the USA, as well as all applicable local building
codes and regulations. Follow all instructions and guidelines
when venting the boiler units. Venting should be performed
only by a licensed professional.
9.1.1 Guidelines for a Common Vent System
CAUTION
●
To ensure the correct operation of the common vent system,
-
a cascade communication cable MUST be installed
between all units in the common vent system by the
installer.
-
backflow vent dampers must be installed in the exhaust
duct of each boiler unit.
-
use direct vent (with separate intake and exhaust vent)
or indirect vent (combustion air drawn from room)
systems.
●
This manual covers the installation of a common vent
system for NFB boilers only.
To ensure the safe and correct installation of the common vent
system, carefully follow the instructions and guidelines.
●
Check to see if all contents are included in the package (refer to
the “Included Items” on page 71).
●
A maximum of 8 NFB boilers may be connected to one common
vent system. In a cascade system that has more than 8 boilers,
use 2 common vent systems, or consult Navien.
●
Use only the PVC cements specified in this manual when
connecting pipes, joints, or elbows.
●
Position the boiler units as close as possible to the vent
termination.
●
Install a new vent system with this appliance. If an existing vent
system is reused, thoroughly inspect it for punctures, cracks, or
blockages prior to connecting it to the boiler unit.
●
Horizontal vent pipe runs must be supported every 4 feet (1.2 m)
(minimum). All vertical vent pipe runs must be supported every
6 feet (1.8 m) (minimum). Support the vent pipe with hangers at
regular intervals or as required by local codes.
●
Install a backflow damper for each boiler unit. Use only the
damper specified in this manual.
●
To avoid moisture and frost build-up and to maintain clearances
to openings on adjacent homes, 45° elbows, 90° elbows, or tees
may be attached to the end of the termination vent pipe to
direct the exhaust plumes away from buildings, as long as the
total allowable vent lengths, maximum number of elbows, and
distances to air intake restrictions are observed.
●
If the boiler units will be installed in areas where snow is known
to accumulate, protect the vent termination from blockage.
Provide a minimum of 1 foot (30 cm) clearance from the bottom
of the exhaust of the expected snow accumulation level. Snow
removal may be necessary to maintain clearance.
●
Ensure that the vent termination is at least 12 in (305 mm) above
ground, 12 in (305 mm) above the highest anticipated snow
level, or as required by local codes, whichever is greater.
●
Support the vent pipe with hangers at regular intervals or as
required by local codes.
●
The vent for this appliance shall not terminate over public
walkways; or near soffit vents or crawl space vents or where
condensate or vapor could create a nuisance or hazard or cause
property damage; or where condensate or vapor could cause
damage or could be detrimental to the operation of regulators,
relief valves, or other equipment.
9. Installing a Common Vent System
