Install Instructions

Type B Gas Vent - 3” to 12” Diameter
Installation Instructions
11
The chimney liner size must not be less than that
specified in the appliance manufacturer’s instructions
or smaller at any point than the connected appliance
flue outlet size. Zero airspace clearance between
the vent and the chimney interior surface is permitted.
The masonry chimney may also have a zero airspace
clearance (direct contact with) combustibles and the
chimney exterior surface. This is permitted with
nominal 4"-width brick. A masonry chimney must
have a clear passageway, sound construction, and
be clean before proceeding. Inspect the chimney
for cracked brick and mortar, missing pieces or holes,
and repair as necessary. To prevent corrosion to the
B-vent, thoroughly clean the chimney of any residual
debris, creosote, or soot that may coat the inside
passageway. The passageway must be at least large
enough to accommodate the proper size B-vent for
the appliance(s).
If there is space remaining in the chimney outside
the liner, this space shall not be used to vent another
appliance unless another liner is used. Minimum
and maximum heights and sizing for B-vent are in
the National Fuel Gas Code. The chimney
termination must meet the requirements of NFPA 211.
Installation
• A tee (RT with a tee cap, RTC) should be used at
the lowest point of the liner. A welded angle iron
frame (by
others)
mortared into
the chimney
walls should be
used with the
support
assembly. (See
Figure 21.) Through-bolt the support assembly
into the frame with 1/4-20 nuts and botls (by
others) in all holes. Place the supporting collar in
the groove at the bottom of the tee just above the
locking ring. (See Figure 8.) Tighten the screw
so that the collar is firmly clamped into position in
the groove. The tee is ready to fit into the support
plate.
• Sixty feet of pipe may be supported by the RSA
support. If more than 60 feet is required, another
support assembly may be used. An adjustable
length (RPA) should be used just below the
Figure 21
resupport to make up for odd dimensions
between supports and to provide for expansion,
if necessary.
• If pipe assemblies are lowered into place from
above, sheet metal screws should be used to hold
the lock bands in place.
• Terminate the vent with a tall cone flashing (RTF),
storm collar (RS), and appropriate diameter cap.
Maintenance and inspection
Gas is a clean-burning fuel that typically does not
require maintenance of appliance vent system.
However, the liner must be inspected at least once
a year by a qualified inspector or installer at the
same time that the appliance is being inspected and
serviced. The cap snaps off for visual inspection of
the outlet area. Connector pipe should be removed
to examine the inlet at the base of the chimney.
Look for loose joints, debris, condensate or
corrosion, and clean or repair as required.
Combined vents
• For detailed instructions for combining two or more
appliances into a common vent, see the Gas Vent
Capacity Tables section in the application guide.
• Whenever possible, vents should be run directly
from collar of the appliance vertically out through
the roof in the most direct method available.
• In those cases where it is necessary or desirable to
combine the vent connectors of several gas-fired
appliances into a common vent, the vent connector
from each individual appliance should be arranged
to have as great a vertical rise as possible before
starting the lat-
eral run to the
common vent. If
a combined vent
cannot be used
because of limi-
tations in the
connector rise or
total vent height,
alternatives such as those illustrated (Figure 22) may
be used to secure greater rise or greater total vent
height. TYPE B GAS VENT CONNECTOR must
be used for Figure 22B.
Figure 22