Installer’s Information Manual
Page 7
INSTALLATION” under the “NON-DIRECT VENTING”
instructions.
A non-direct vented furnace takes all air for combustion
from the room in which furnace is installed. Non-direct
venting requires only one pipe for venting the flue gases to
the outdoors but you must make sure there is enough air for
combustion and ventilation.
DIRECT VENTING INSTRUCTIONS (two
pipe system)
DETERMINING VENT LENGTH
See Table 1 for maximum vent and combustion-air pipe
length. Include any termination elbows when determining
maximum allowable vent length. Minimum vent length is
five feet with 0 elbows.
Table 1 shows the maximum allowable pipe lengths for
direct vent systems depending on:
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altitude (elevation) of the installation
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gas input rating of furnace
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diameter of the air and vent pipes
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number of elbows
Note that some of the larger furnace models may require a
high altitude pressure switch at elevations between 3000
and 6000 feet. For example, the table shows that the
126,000 Btu/hr model may need a high altitude pressure
switch when installed at elevations between 3000 and 4000
feet. Above 4000 feet, this model requires a high altitude
switch for all installations.
All furnace models require the high altitude pressure switch
when installed at elevations above 6000 feet.
The high-altitude pressure switch is supplied with the LP
Conversion Kit #4226000 and the Natural Gas Conversion
Kit #4225600. These kits also contain the other
components required for furnace installation at high
elevations.
NOTE: Table 1 assumes Sweep 90
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elbows like that in
Figure 3a. If using Hard 90
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elbows similar to the one in
Figure 3b, decrease the vent length by 3 feet for every
elbow used.
(a)
(b)
Figure 3. (a) Sweep 90
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Elbow. (b) Hard 90
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Elbow.
When using a concentric vent kit the following exceptions
apply:
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90,000 BTU input furnaces must be vented with 3 -inch
pipe.
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For 108,000 BTU input furnaces, reduce the maximum
vent length by 5 feet when 2 sweep elbows are used,
10 feet when 3 sweep elbows are used, 15 feet when 4
sweep elbows are used and so on. For hard 90°
elbows reduce vent length in 8 -foot intervals.
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126,000 BTU input furnaces may not be vented using a
concentric vent.
