Navien NHB H Series Installation And Operation Manual page 78

9.1.1 Guidelines for a Common Vent
System
WARNING
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.
Common vent installations for use with
●
natural gas and propane are only approved
for up to 4,500 ft.
This manual covers the installation of a
●
common vent system for NHB-H 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
82).
A maximum of 8 NHB-H 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 Navien Backflow Damper Kit for each
●
boiler unit. Use only the damper specified in this
manual.
78 Installing a Common Vent System
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
●
(300 mm) above ground, 12 in (300 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 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.