PRODUCT DESIGN
39
Fix 4 - Relining.
Relining options include B vent and flexible liners.
If the chimney has diagonal offsets, B vent probably cannot
be used.
If B vent is to be used, it must be supported adequately.
Supports (such as fire stops or thimbles) must be used to
prevent the B vent from coming into direct contact with the
tile liner or chimney walls. Direct contact would result in
higher heat loss, with an increased possibility of poor vent-
ing system performance.
It is not acceptable to vent one appliance inside the B vent
and other appliances outside. The excess space between
the B vent and the chimney walls must be covered at the top
of the chimney by a weatherproof, corrosion resistant flash-
ing.
The B vent should then be topped with a listed vent cap. The
listed vent cap will, when installed per the manufacturer’s
instructions, prevent problems due to rain, birds, or wind
effects.
A B vent installed as described in this section is considered
to be an enclosed vent system, and the sizing tables in
National Fuel Gas Code NFPA 54/ANSI Z223.1 - latest edi-
tion and in the National Standard of Canada, CAN/CGA
B149.1 and CAN/CGA B149.2 - latest editions and amend-
ments may be used.
If a flexible liner is to be used, it must be made of the proper
materials:
• For most residential applications, an aluminum liner
should be acceptable.
• If the combustion air supplied to the furnace will be
contaminated with compounds containing chlorine or
fluorine, a liner of AL29-4C stainless steel should be
used. Common sources of chlorine and fluorine com-
pounds include indoor swimming pools and chlorine
bleaches, paint strippers, adhesives, paints, varnishes,
sealers, waxes (which are not yet dried) and solvents
used during construction and remodeling. Various com-
mercial and industrial processes may also be sources
of chlorine/fluorine compounds.
• Heavier gauge 300 and 400 series stainless steel lin-
ers were developed for use with oil or solid fuel appli-
ances. They are not suitable for use with gas-fired
appliances. Flexible liners specifically intended and
tested for gas applications are listed in the UL "Gas
and Oil Equipment Directory". (UL Standard 1777).
For sizing of flexible liners, see Note 22 and the tables in
the National Fuel Gas Code NFPA 54/ANSI Z223.1 - latest
edition and in the National Standard of Canada, CAN/CGA
B149.1 and CAN/CGA B149.2 - latest editions and amend-
ments.
To install the liner, read and follow the liner manufacturer’s
instructions and your local codes. Excess liner length should
be pulled out of the chimney and cut off. Use caution when
doing this, as the cut edges of flexible liners may be sharp.
Do not spiral excess liner inside of the chimney. Support
the liner as recommended by the liner manufacturer.
Some manufacturers of flexible liners offer an insulation sleeve
designed to be added to the liner before it is installed in the
chimney. (Poured insulation, either vermiculite or other ma-
terials, is no longer recommended.) Insulation will need to
be added to the flexible liner if:
• It is required by the liner manufacturer’s instructions.
• The previous liner was properly sized and installed,
and suffered from condensation damage.
• It is required by your local building codes.
Even if none of those three conditions exist which require
additional liner insulation, the installer may wish to consider
it if:
• The local climate is very cold.
• The chimney is very tall.
• The vent connectors used are very long or have a large
number of elbows.
• Local experience indicates that flexible liners installed
without insulation are likely to have condensation prob-
lems.
Insulation must be selected and installed in accordance with
the liner manufacturer’s instructions.
Finally, cap the chimney and terminate the liner in accor-
dance with the liner manufacturer’s instructions.
Horizontal Applications and Considerations
Horizontal applications, in particular, may dictate many of
the installation’s specifics such as airflow direction, duct-
work connections, flue and/or combustion air pipe connec-
tions, etc. The basic application of this furnace as a hori-
zontal furnace differs only slightly from an upright installa-
tion. When installing a furnace horizontally, additional con-
sideration must be given to the following:
ALTERNATE VENT/FLUE
AND COMBUSTION AIR
INTAKE LOCATIONS
FURNACE MUST BE LEVEL
FROM END TO END
FURNACE MUST BE LEVEL
OR SLIGHTLY TILTED FORWARD
WITH THE DOORS 0" - 3/4"
BELOW THE BACK PANEL
DRAIN LINE WITH 1/4" PER FOOT
DOWNWARD SLOPE
36" MINIMUM SERVICE
CLEARANCE REQUIRED
FURNACE MUST BE SUPPORTED
AT BOTH ENDS AND MIDDLE
DRAIN PAN
GAS LINE WITH
DRIP LEG (3" MINIMUM)
4 3/4" MINIMUM
DRAIN TRAP
CLEARANCE
(90% Furnaces Only)
(90% Furnaces Only)
(90% Furnaces Only)
(90% Furnaces Only)
(90% Furnaces Only)
90% Horizontal Furnace Shown
(80% Horizontal Furnace Similar)
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