Exterior
Masonry
Chimney,
FAN+NAT
Installations
with
Type-B
Double-Wall
Vent
Connectors
VENT
HEIGHT
(FT)
6
8
10
15
20
30
VENT
HEIGHT
(FT)
6
8
o
10
2O
30
_"
10
0
,_
15
20
30
6
8
o
10
o
is
i
2O
© NFPA& AGA
Table A-
Combined
Appliance
Maximum Input Rating in
Thousands
of Btu per Hr
INTERNAL
AREA OF
(SQ IN.)
12
19
28
74
119
178
80
130
193
84
138
207
NR
152
233
NR
NR
250
NR
NR
NR
CHIMNEY
Table B-
Minimum Allowable
Input Rating of
Space-Heating
Appliance
in
Thousands
of Btu per Hr
38
257
279
299
334
368
404
INTERNAL
AREA OF CHIMNEY
(SQ IN.)
12
19
28
38
Local 99% Winter Design Temperature:
17 to 26 ° F*
0
55
99
141
52
74
111
154
NR
90
125
169
NR
NR
167
212
NR
NR
212
258
NR
NR
NR
362
Local 99% Winter
Design Temperature:
5 to 16° F*
NR
78
121
166
NR
94
135
182
NR
111
149
198
NR
NR
193
247
NR
NR
NR
293
Inspections
before the sale a nd at the time of installation
will deter-
mine the acceptability
of the chimney
or the need for repair and/or
(re)lining.
Refer to the Chimney
Inspection
Chart
to perform
a
chimney
inspection.
If the inspection
of a previously
used tile-lined
chimney:
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 or Type-B
vent to reduce
condensation.
If
a condensate
drain
is required
by local code,
refer to the
NEGC,
Section
10.9 for additional
information
on conden-
sate 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 con-
dition, shall be rebuilt to conform
to AN SI/N FPA 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 consid-
ered 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
NR
NR
NR
377
Local 99% Winter Design Temperature:
-10 to 4° F*
NR
NR
145
196
NR
NR
159
213
NR
NR
175
231
NR
NR
NR
283
NR
NR
NR
333
NR
NR
NR
NR
Appliance
operation
has a significant
impact
on the performance
of the venting
system.
If the appliances
are sized,
installed,
ad-
justed,
and operated
properly,
the venting
system
and/or
the ap-
pliances
should
not suffer
from condensation
and corrosion.
The
venting
system
and all appliances
shall be installed
in accordance
with applicable
listings,
standards,
and codes.
30
-11 ° F
Local 99% Winter
Design Temperature:
-11 ° F or
or
lower*
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% beating db temper-
atures found in the 1997 or 2001 ASHRAE Fundamentals Handbook,
Climatic Design Information chapter, Table 1A (United States) and 2A
(Canada).
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 or liner must be in
good condition
and be installed
in accordance
with the vent or liner
manufacturer's
instructions.
To prevent
condensation
in the furnace
and vent system,
the fol-
lowing
precautions
must be observed:
1.
The return-air
temperature
must be at least 60°F db except
for brief periods
of time during
warm-up
from setback
at no
lower than 55°F db or during
initial start-up
from a standby
condition.
Adjust
the gas input
rate per the installation
instructions.
Low gas input rate causes
low vent gas temperatures,
ca us-
ing condensation
and corrosion
in the furnace
and/or
vent-
ing system.
Derating
is permitted
only for altitudes
above
2000'.
3.
Adjust
the air temperature
rise to the midpoint
of the rise
range or slightly
a hove.
Low air temperature
rise ca n ca use
low vent gas temperature
and potential
for condensation
problems.
4.
Set the thermostat
heat anticipator
or cycle rate to reduce
short
cycling.
Air for combustion
must not be contaminated
by halogen
com-
pounds
which include
chlorides,
fluorides,
bromides,
and iodides.
These
compounds
are found
in many
common
home
products
such as detergent,
paint, glue, aerosol
spray, bleach,
cleaning
sol-
vent, salt, and air freshener,
and can cause corrosion
of furnaces
and vents.
Avoid
using such products
in the combustion-air
sup-
441 01 2314 02
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