Canada (and U.S.A.)-This furnace is permitted to be vented into
a clay tile-lined masonry chimney that is exposed to the outdoors
below the roof line, provided:
1. Vent connector is Type-B double-wall, and
2. This furnace is common vented with at least 1 draft hood-
equipped appliance, and
3. The combined appliance input rating is less than the maximum
capacity given in Table A, and
4. The input rating of each space heating appliance is greater
than the minimum input rating given in Table B for the local
99% Winter Design Temperature. Chimneys having internal
areas greater than 38 square inches require furnace input
ratings greater than the input ratings of these furnaces. See
footnote at bottom of Table B, and
5. The authority having jurisdiction approves.
If all of these conditions cannot be met, an alternative venting
design shall be used, such as the listed chimney adapter kit with
these furnaces, which are listed for use with the kit, a listed
chimney-lining system, or a Type-B common vent.
Inspections before the sale and at the time of installation will
determine the acceptability of the chimney or the need for repair
and/or (re)lining. Refer to the Fig. 33 to perform a chimney
inspection. If the inspection of a previously used tile-lined chim-
ney:
a. Shows signs of vent gas condensation, the chimney should
be relined in accordance with local codes and the authority
having jurisdiction. The chimney should be relined with a
listed metal liner, Type-B vent, or a listed chimney adapter
kit shall be used to reduce condensation. If a condensate
drain is required by local code, refer to the NFGC, Section
10.9 for additional information on condensate drains.
b. Indicates the chimney exceeds the maximum permissible
size in the tables, the chimney should be rebuilt or relined
to conform to the requirements of the equipment being
installed and the authority having jurisdiction.
A chimney without a clay tile liner, which is otherwise in good
condition, shall be rebuilt to conform to ANSI/NFPA 211 or be
lined with a UL listed (ULC listed in Canada) metal liner or UL
listed Type-B vent. Relining with a listed metal liner or Type-B
vent is considered to be a vent-in-a-chase.
If a metal liner or Type-B vent is used to line a chimney, no other
appliance shall be vented into the annular space between the
chimney and the metal liner.
APPLIANCE APPLICATION REQUIREMENTS
Appliance operation has a significant impact on the performance
of the venting system. If the appliances are sized, installed,
adjusted, and operated properly, the venting system and/or the
appliances should not suffer from condensation and corrosion. The
venting system and all appliances shall be installed in accordance
with applicable listings, standards, and codes.
The furnace should be sized to provide 100 percent of the design
heating load requirement plus any margin that occurs because of
furnace model size capacity increments. Heating load estimates
can be made using approved methods available from Air Condi-
tioning Contractors of America (Manual J); American Society of
Heating, Refrigerating, and Air-Conditioning Engineers; or other
approved engineering methods. Excessive oversizing of the fur-
nace could cause the furnace and/or vent to fail prematurely.
When a metal vent or metal liner is used, the vent must be in good
condition and be installed in accordance with the vent manufac-
turer’s instructions.
Exterior Masonry Chimney FAN + NAT
Installations with Type-B Double-Wall Vent
Connectors
©NFPA & AGA
Table A—Combined Appliance Maximum Input
Rating in Thousands of BTU per Hour
VENT HEIGHT (FT)
INTERNAL AREA OF CHIMNEY
(SQ. IN.)
12 19 28 38
6 74 119 178 257
8 80 130 193 279
10 84 138 207 299
15 NR 152 233 334
20 NR NR 250 368
30 NR NR NR 404
Table B—Minimum Alowable Input Rating of
Space-Heating Appliance in
Thousands of BTU per Hour
VENT
HEIGHT (FT)
INTERNAL AREA OF CHIMNEY
(SQ. IN.)
12 19 28 38
Local 99% Winter Design
Temperature: 17 to 26 degrees F*
17 to 26°F
6 0 55 99 141
8 52 74 111 154
10 NR 90 125 169
15 NR NR 167 212
20 NR NR 212 258
30 NR NR NR 362
Local 99% Winter Design
Temperature: 5 to 16 degrees F*
5to16F
6 NR 78 121 166
8 NR 94 135 182
10 NR 111 149 198
15 NR NR 193 247
20 NR NR NR 293
30 NR NR NR 377
Local 99% Winter Design
Temperature: -10 to 4 degrees F*
-10to4F
6 NR NR 145 196
8 NR NR 159 213
10 NR NR 175 231
15 NR NR NR 283
20 NR NR NR 333
30 NR NR NR NR
Local 99% Winter Design
Temperature: -11 degrees F or lower*
-11 F or lower
Not recommended for any vent
configuration
*The 99% Winter Design Dry-Bulb (db) temperatures are found in the 1993
ASHRAE Fundamentals Handbook, Chapter 24, Table 1 (United States) and
2 (Canada), or use the 99.6% heating db temperatures found in the 1997 or
2001 ASHRAE Fundamentals Handbook, Climatic Design Information chap-
ter, Table 1A (United States) and 2A (Canada).
27
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