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5. Installing a Common Vent System
5.1 About the Common Vent System
The Navien Common Vent System* provides an easy way to install
the vent system for up to 8 Navien NPE water heater 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 Navien NPE
water heater units.
DANGER
Category IV appliances require a special venting system. The
vent system will operate with a positive pressure in the pipe.
Exhaust gases must be piped directly outdoors using the
vent materials and rules outlined in these instructions. Do not
connect vent connectors serving appliances vented by natural
draft into any portion of mechanical draft systems operating
under positive pressure. Follow the venting instructions
carefully. Failure to do so will result in substantial property
damage, severe personal injury, or death.
WARNING
Improper venting of the water heater units can result in
excessive levels of carbon monoxide, which can lead to
severe personal injury or death. The water heater 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
water heater units. Venting should be performed only by a
licensed professional.
The venting system must be sealed gastight to prevent flue
gas spillage and carbon monoxide emissions, which will
result in severe personal injury or death.
The building owner is responsible for keeping the exhaust
and intake terminations free of snow, ice, or other potential
blockages, as well as scheduling routing maintenance.
Blocked or obstructed vent piping terminations could result
in property damage, severe personal injury, or death.
5.1.1 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 water heater unit.
This section covers the installation of a common vent system
for NPE water heaters 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 53).
A maximum of 8 NPE water heaters may be connected to one
common vent system. In a cascade system that has more than 8
water heaters, use 2 common vent systems, or consult Navien.
Use the proper PVC cements and adhesives that are
recommended for use by the pipe manufacturer.
Position the water heater 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 water heater unit.
The common vent system covered in this manual is approved for
direct and non-direct vent applications.
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
the indicated intervals or as required by local codes.
Install a backflow damper for each water heater 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 water heater 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.
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.
Installing a Common Vent System
49
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