32 Installing the Water Heater
3.6.3 Measuring Vent Length
The maximum vent length when using 2 in exhaust ducts is 60 ft.
The maximum vent length when using 3 in vent ducts is 150 ft.
The intake duct length can be of equal length to the exhaust duct
length. Both maximum lengths are reduced by the number of
elbows used, as shown in the following table:
Vent Size
Maximum
Length
Maximum
# of Elbows
Equivalent Lengths
2 in
60 ft
(18 m)
6
Reduce the maximum
vent length
accordingly for each
elbow used:
Each 90° elbow
equates to 8 linear
ft (2.4 m) of vent
Each 45° elbow
equates to 4 linear
ft (1.2 m) of vent
3 in
150 ft
(45 m)
8
Reduce the maximum
vent length
accordingly for each
elbow used:
Each 90° elbow
equates to 5 linear
ft (1.5 m) of vent
Each 45° elbow
equates to 3 linear
ft (0.9 m) of vent
Note
The Maximum Length does not include any elbows.
If using a concentric termination as shown on
pages33-34, count this as 5 linear ft (1.5 m) of
vent.
The maximum vent lengths at high altitudes are
the same as shown in the table above.
3.6.2 Selecting Vent Pipe Materials
Venting requirements differ in the US and Canada. Consult the
following chart or the most recent edition of ANSI Z223.1/NFPA
54 or CAN/CGA B149.1, as well as all applicable local codes and
regulations when selecting vent pipe materials. Do not use cellular
core based pipe materials for the exhaust vent.
Locale Recommended Vent Materials
USA
PVC Schedule 40 (Solid Core)
CPVC Schedule 40 or 80 (Solid Core)
Approved Polypropylene*
Canada**
Type BH Special Gas Vent Class IIA (PVC)
Type BH Special Gas Vent Class IIB (CPVC)
Type BH Special Gas Vent Class IIC
(Polypropylene)
* Approved polypropylene systems include:
Duravent Polypro (Single Wall): 2PPS-xxx (2 in), 3PPS-xxx (3 in)
Centrotherm Innoflue SW: ISxx02xx (2 in), ISxx03xx (3 in)
Refer to manufacturer’s literature for detailed information.
** For installation in Canada, field-supplied plastic vent piping must comply
with CAN/CGA B149.1 (latest edition) and be certified to the Standard
For Type BH Gas Venting Systems, ULC-S636. Components of this listed
system must not be interchanged with other vent systems or unlisted
pipes or fittings. All plastic components and specified primers and glues
of the certified vent system must be from a single system manufacturer
and must not be intermixed with another system manufacturer’s parts.
The supplied vent connector and vent termination are certified as part of
the water heater.
CAUTION
This water heater has a built-in control to limit the exhaust
temperature to 149 °F (65 °C). As a result, the Navien water
heater can be vented with Schedule 40 PVC. If the incoming
(or recirculation return) water temperature does not exceed
150 °F (66 °C), the exhaust temperature will not exceed
149 °F (65 °C).
However, if you set the water heater at a temperature
above 150 °F (66 °C) and you are also incorporating either
an external recirculation loop or a combination heating
system, the exhaust temperature can exceed 149 °F (65 °C).
In that case, you must use Schedule 40 or 80 CPVC or
Approved Polypropylene in the USA or Type BH Special
Gas Vent Class IIB (CPVC) or Class IC (Polypropylene) that
conforms to ULC-S636 in Canada.
In systems with 2 in vents, if the exhaust temperature
exceeds 149 °F (65 °C), CPVC pipe (field supplied) must
be used for the first 3 ft of equivalent pipe length. For
systems with 3 in vents, if the exhaust temperature exceeds
149 °F (65 °C), CPVC pipe (field supplied) must be used for
the first 5 in of equivalent pipe length.
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