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The maximum recommended chimney height in all
applications which include the vent adapter is 35 feet
(10.6m).
Vent connector from the vent adapter to the tile−lined
chimney must be constructed of type B, double−wall vent
pipe.
The furnace vent connector rise shall not exceed 3 feet
(.9m).
Vent connector lateral length must not exceed 18"
(457mm) for each inch of vent connector diameter. For
example, a 6" (152mm) diameter vent connector would
have a maximum lateral length of 9 feet (2.7m).
Vent connectors should not be sized more than two sizes
greater than the listed appliance categorized vent
diameter, flue collar diameter, or drafthood outlet
Type B Double Wall Vent Connector Serving a Single 80AF1UH, ML180UH, EL280UH or SL280UH Furnace
Vent
Height
H
(ft)
6
8
10
15
20
30
35
Minimum internal area of chimney (in.
Maximum internal area of chimney (in.
TABLE 3
Interior Masonry Chimney Only
with Masonry Chimney Vent Adapter Kit
Type B Double Wall Vent Connector Diameter − (inches)
to be used with chimney areas within the size limits at bottom
Lateral
L
(ft)
2
5
2
5
8
2
5
8
2
5
10
12
2
5
10
12
2
5
10
12
2
5
10
12
MASONRY CHIMNEY INTERNAL AREA
2
)
2
)
diameter.
The vent sizing tables allow for two 90° turns. For each
additional turn, or equivalent, reduce the maximum
capacity listed in the venting tables by 10 percent (.90 X
maximum table capacity).
Interpolation is permitted when calculating capacities for
vent dimensions that fall between table entries; however,
extrapolation beyond the table entries is not permitted.
Size the chimney and vent connector per table 3 and
figure 2 when a single appliance is being vented into an
interior masonry chimney. Size the chimney and vent
connector per tables 4 and 5 and figure 3 when using an
interior or exterior masonry chimney as a common vent
serving multiple appliances.
Use table 6 to determine the equivalent area of masonry
chimney liners.
6 in.
Appliance Input Rate in Thousands of Btu per Hour
NAT
Max
130
117
145
134
127
162
148
139
179
164
153
148
210
184
172
167
216
198
184
179
225
206
192
186
38
198
Page 3
7 in.
8 in.
NAT
NAT
Max
Max
180
247
165
231
198
266
183
247
175
239
221
298
204
277
191
263
250
336
231
313
216
296
210
290
274
375
254
350
237
332
230
325
303
421
281
393
263
373
255
365
315
435
291
406
273
386
265
378
50
269
352
63
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