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Venting - Continued
6- Clearance to combustible material is 6" (152 mm) for
single wall vent material except where a listed
clearance thimble is used. Clearance to combustible
material for type B-1 vent or factory-built chimney is
per manufacturer’s instructions.
7- The vent connector shall be supported without any dips
or sags. Vertical vents shall be supported in
accordance with their listing and manufacturers’
instructions. All horizontal vent connector runs shall
have a slope up to the vertical vent of at least 1/4" per
foot (1 mm per 50 mm).
8- All vertical type B-1 vents, single wall vents, or listed
chimney lining system must be terminated with a listed
vent cap or listed roof assembly.
9- The vent must extend at least 3' (1 m) above the
highest point where it passes through a roof of a
building and at least 2’ (0.6 m) higher than any part of
a building within a horizontal distance of 10' (3.05 m)
unless otherwise specified by the (American) National
Fuel Gas Code, ANSI Z223.1 or (Canada) CAN/CGA-
B149 Installation Codes. The vent must extend at least
5' (1.6 m) above the highest connected equipment flue
collar.
1- If possible, do not terminate the horizontal vent through
a wall that is exposed to prevailing wind.
C-Horizontal Venting - General
Common venting is not allowed when horizontally venting
the unit heater.
The minimum horizontal vent length is three feet (914
mm).
2- Exposure to excessive winds can affect unit
performance. If such a termination is necessary, use a
wind block to protect the vent termination from direct
winds.
3- Vent termination must be free from obstructions and at
least 12" (306 mm) above grade level and maximum
snow height.
4- Do not terminate vent directly below roof eaves or
above a walkway, or any other area where condensate
dripping may be troublesome and may cause some
staining. Avoid windows where steam may cause
fogging or ice buildup.
5- When horizontally vented, minimum clearance for
termination from any door, window, gravity air inlet, gas
or electric meter, regulators, and relief equipment is 4
ft (1.2 m) for U.S. installations. Refer to NFPA 54/ANSI
Z223.1 in the U.S.A. and CAN/CGA B149.1 and .2 in
Canada or with authorities having local jurisdiction.
In Canada, vent termination must have a minimum 6 ft
(1.8mm) horizontal clearance from gas and electric
meters and relief devices as specified in the Canadian
B149.1, Natural Gas Installation Code.
5- Vent termination must be a minimum of 4' (1.2m)
below or 4’ (1.2m) horizontally from any soffit vent or
under-eave vent.
6- Vent must be a minimum of 6' from an inside corner
formed by two exterior walls. If possible, leave a 10'
clearance.
7- Vent termination must be a minimum of 10' (3m) from
any forced air inlet (includes fresh air inlet for other
appliances, such as a dryer).
8- When termination is routed through an exterior
combustible wall the vent must be supported using a
listed clearance thimble. Where local authorities
permit, a single section of type B-1 vent pipe may be
used as an alternative to the thimble. When using a
type B-1 vent termination use the clearances specified
by the vent manufacturer. Seal the connection between
the single wall and double wall pipes and the annular
space of the double wall pipe as shown in Figure 2.
Inside edge of vent termination tee must be at least
12”es from outside wall as shown in Figure 3.
9- All horizontal vents must terminate with a tee. Opening
end must face downward. Addition of ¼” (6 mm) mesh
corrosion resistant material as a bird screen in the tee
openings may be used.
10- For horizontal venting, the vent pipe shall be supported
with hangers no more than 3 ft (1 m) apart to prevent
movement after installation.
1- Horizontal commercial installations are for buildings
which are not attached to living spaces. The vent may
be single wall vent material installed according to the
sections Venting A - General Recommendations
and Requirements and C - Horizontal Venting -
General and D - Horizontal Venting - Commercial.
Refer to Figures 3, 4, and 5.
D-Horizontal Venting-Commercial
2- The vent pipe diameter for horizontal commercial
installations shall be 3” (76 mm) on 30/45 units and 4”
(100 mm) on 60/75 units. In all cases, a flue transition
piece (supplied) is required to fit over the outlet of the
induced draft assembly on the appliance.
3- Refer to Table 2 for maximum vent connector lengths.
4- Select a wall termination point that will maintain ¼” rise
per foot slope of horizontal run of vent pipe. The vent
may be single wall material minimum 26 GSG (0.46
mm) galvanized steel or equivalent grade stainless
steel. Seal single wall vent material according to the
section A-General Recommendations and
Requirements. In areas where local authorities having
