Selecting Vent Pipe Materials; Measuring Vent Length - Navien NHB-055 Installation & Operation Manual

5.2 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 PVC (ASTM F891), cellular core CPVC, or Radel®
(polyphenolsulfone) for the exhaust vent.
Locale Recommended Vent Materials
PVC Schedule 40 (Solid Core)
USA CPVC Schedule 40 or 80 (Solid Core)
Approved polypropylene
Type BH Special Gas Vent Class IIA (PVC)
Type BH Special Gas Vent Class IIB (CPVC)
Canada*
Type BH Special Gas Vent Class IIC
(polypropylene)
* 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 boiler.
** Approved Polypropylene Systems include:
Duravent Polypro (Single Wall) : 2PPS-xxx (2"), 3PPS-xxx (3")
Centrotherm InnoFlue SW: ISxx02xx (2"), ISxx03xx (3")
Refer to manufacturer's literature for detailed installation instructions.
For 3" venting, use the following polypropylene parts:
Duravent: 2PPS-X3L (2"-3" Increaser)
Centrotherm: ISEI0203 or ISIA0203 (2"-3" Increaser)
CAUTION
This boiler has a built-in control to limit the exhaust
temperature to 149°F (65°C). As a result, the boiler can be
vented with Schedule 40 PVC.
In high temperature applications, 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 (CPCV) 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 feet 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.
If you require that return water hotter than 140°F (60°C) to circulate
back to boiler, the DIP switch must be configured (Dip Switch 2,
switch #8 to ON position). Otherwise, the boiler will control and
maintain the flue and DHW temperature below 150°F (65°C) and
**
**
140°F (60°C) respectively.
When PCB DIP switch 2 #8 is set to Off (factory
Note
default), the boiler does not operate without an
exhaust thermostat installed.
When you set PCB DIP switch 2 #8 to On, ensure
that CPVC piping is used for exhaust venting.
ON
1 2 3 4 5 6

5.3 Measuring Vent Length

The maximum vent length when using 2 in exhaust ducts is 60 ft
(18 m). The maximum vent length when using 3 in vent ducts
is 150 ft (45 m). The intake duct length may be identical to the
exhaust duct length. Maximum vent lengths reduces according to
the number of elbows used, as shown in the following table:
Maximum
Vent Size
Length # of Elbows
2 in 60 ft (18 m)
3 in 150 ft (45 m)
The Maximum Length does not include any elbows.
Note
If using a concentric termination as shown on
page 47, count this as 5 linear feet (1.5 m) of vent.
ON
1 2 3 4 5 6 7 8
Maximum
Equivalent Length
Reduce the
maximum vent
length accordingly
for each elbow used:
Each 90° elbow
6
equates to 8 linear
feet of vent
Each 45° elbow
equates to 4 linear
feet of vent
Reduce the
maximum vent
length accordingly
for each elbow used:
Each 90° elbow
8
equates to 5 linear
feet of vent
Each 45° elbow
equates to 3 linear
feet of vent
Venting the Boiler 45