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Common Vent
3
(Indoor Units Only. Direct Vent and
Non-Direct/Room Air Vent)
Common venting allows multiple Rinnai Tankless
Water Heaters to share the same vent system.
Rinnai water heaters can only be common vented
with Schedule 40 PVC/CPVC or with the Rinnai
certified common vent system.
Figure 39
Example: Rinnai Common Venting
Example: Schedule 40 PVC/CPVC
Common Vent
General Guidelines
When installing Common Vent, follow these
guidelines:
• Use only the materials listed in this manual
for vent, air intake pipe, and fittings. Failure to
comply with this warning could result in
property damage, personal injury, or death.
• When cutting vent components, ensure that
the cuts are straight.
• Chamfer and deburr all edges before
installing the components.
• Vent joints must not leak. Confirm gas tight
connections of every vent joint.
• Before operating the water heater(s), ensure
vent system is clean and free of debris.
Demand Duo
H-Series with SENSEI CX Installation Instructions
• Vent system must be supported according to
the vent manufacture's installation
instructions.
• Venting should be as direct as possible with
a minimum number of fittings.
• The common vent system must only be
installed by a trained and qualified
professional.
Common Vent Termination Clearances
• Vent termination per ANSI Z223.1/NFPA 54.
For clearances not specified in ANSI Z223.1/
NFPA 54, clearances are in accordance with
local installation codes and the requirements
of the gas supplier.
WARNING
DO NOT slope the combustion air pipe
toward unit. Failure to comply with this
warning could result in property damage,
personal injury, or death.
DO NOT apply PVC/CPVC glues, solvents,
or cleaners to the tankless water heater's
intake or exhaust gasket connections.
Failure to correctly assemble the
components according to these instructions
may result in property damage, personal
DO NOT obstruct combustion air flow or
exhaust gas flow in the venting system.
DO NOT install the water heater in an area
with negative air pressure.
DO NOT combine the common vent system
with existing vents, chimneys, or vent pipes
connected to other water heaters, boilers or
appliances.
DO NOT common vent different Rinnai
models in a single common vent system.
DO NOT use cellular core PVC/CPVC,
Radel or galvanized materials.
DO NOT combine vent components from
different manufacturers.
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