Lennox DAVE LENNOX SIGNATURE SL297UHNV, Руководство по установке

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Page 15
NOTE - In Direct Vent installations, combustion air is tak-
en from outdoors and flue gases are discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
tables 4 and 5. Count all elbows inside and outside the
home. Table 4 lists the minimum vent pipe lengths per -
mitted. Table 5 lists the maximum pipe lengths permitted.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination
pipe is sized to optimize the velocity of the exhaust gas as
it exits the termination. Refer to table 8.
In some applications which permit the use of several dif-
ferent sizes of vent pipe, a combination vent pipe may be
used. Contact Lennox’ Application Department for assis-
tance in sizing vent pipe in these applications.
Horizontal Installation Offset Requirements
NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE -
ward unit. A minimum of 1/4” (6mm) drop for each 12” (305mm)
of horizontal run is mandatory for drainage.
NOTE - Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
12” ma x
of straight pip e
Exhaust Pipe
12” Min.
Horizontal
Gas Furnace
FIGURE 18
TABLE 4
MINIMUM VENT PIPE LENGTHS
SL297UHNV Model MIN. VENT LENGTH*
040, -060, -080
15 ft. or 5 ft. plus 2 elbows
or 10 ft. plus 1 elbow
*Any approved termination may be added to the minimum
length listed.
Use the following steps to correctly size vent pipe diam-
eter.
Piping Size Process
1
2
3
4
5
6
Which style termination
being used?
Standard or concentric?
See table 3.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
2” or 3”
Use table 5 or 6 to find
max intake or exhaust pipe
length. Includes all vent
pipe and elbows inside
and outside the house.
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
040, 060, 080?
FIGURE 19
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.