GM9S80 Service Manual
SYSTEM OPERATION
19
If Checks 1 through 6 have been satisfactory, and the liner is
an acceptable size as determined by the tables in 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 amendments, then
the clay tile liner can probably be used as a vent for the gas
appliances. However, the installer must keep in mind the
following factors which may render the tile liner unsuitable
for use as a vent:
•
• Long vent connectors
• Masonry chimneys with no air gap between the liner
detect.)
•
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 amendments
assume interior chimneys.)
If in the judgment of the local gas utility, installer, and/or local
codes, one or more of the above factors is likely to present a
Any cap or roof assembly used with a liner must be ap-
proved by the liner manufacturer for such use. The liner and
cap/roof assembly must then terminate above the roof in ac-
cordance with the manufacturer’s instructions.
possible with a liner than would be required with a masonry
If the masonry chimney has more than one channel, it may
be possible to vent the gas appliances into one channel and
vent the solid or liquid fuel appliance(s) into another chan-
nel(s). Do not vent an 80% furnace inside of a metal liner
with other appliances vented outside the liner.
Alternatively, the homeowner may agree to discontinue use
-
ing must then be permanently sealed.
-
fuel oil residue.
If none of the above options are practical, the 80% furnace
may need to be vented vertically with B vent.
Under some conditions a 90%+ furnace could be installed
rather than an 80%. The 90% furnace can be vented hori-
zontally or vertically through PVC pipe.
repair it in accordance with nationally recognized building
codes or standards. One such standard which may be refer-
enced is the Standard for Chimneys, Fireplaces, Vents, and
Solid Fuel Burning Appliances, ANSI/NFPA 211.
be used.
If B vent is to be used, it must be supported adequately.
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
B vent and the chimney walls must be covered at the top of
The B vent should then be topped with a listed vent cap. The
listed vent cap will, when installed per the manufacturer’s in-
A B vent installed as described in this section is considered
to be an enclosed vent system, and the sizing tables in Na-
tional 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 amendments
may be used.
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
compounds include indoor swimming pools and
chlorine bleaches, paint strippers, adhesives, paints,
and solvents used during construction and remodeling.
Various commercial and industrial processes may also
• Heavier gauge 300 and 400 series stainless steel liners
were developed for use with oil or solid fuel appliances.