WARNING:
Do not bend duct flanges inward as shown.
This will affect airflow across heat exchangers and may
cause limit cycling or premature heat exchanger failure.
Remove duct flange completely or bend it inward a
minimum of 210° as shown.
II.
FILTER ARRANGEMENT
CAUTION:
Never operate unit without a filter or with
blower access panel removed.
Factory-supplied washable framed filter is shipped in blower
compartment. Determine location for filter and relocate filter
retaining wire if necessary. See Table 3 to determine correct filter
size for desired filter location. Table 3 indicates filter size,
location, and quantity shipped with this furnace. See Fig. 1 for
location and size of top return-air opening.
III.
GAS PIPING
Gas piping must be installed in accordance with national and local
codes. Refer to current edition of NFGC. Canadian installations
must be made in accordance with NSCNGPIC and all authorities
having jurisdiction. Gas supply line should be a separate line
running directly from meter to furnace, if possible. Refer to Table
4 for recommended gas pipe sizing. Risers must be used to connect
to furnace and to meter. Support all gas piping with appropriate
straps, hangers, etc. Use a minimum of 1 hanger every 6 ft. Joint
compound (pipe dope) should be applied sparingly and only to
male threads of joints. Pipe dope must be resistant to propane gas.
CAUTION:
Connect gas pipe to furnace using a backup
wrench to avoid damaging gas controls.
WARNING:
Gas valve shutoff switch MUST be facing
forward or tilted upward. Failure to follow this warning
could result in property damage or death.
Fig. 11—Duct Flanges
A93029
NO
YES
YES
PERFORATED
DISCHARGE DUCT
FLANGE
210°
MIN
TABLE 3—FILTER INFORMATION
FURNACE
CASING
WIDTH (IN.)
FILTER SIZE (IN.)
FILTER TYPE
FRAMED
Top Return
17-1/2
(1) 16 X 25 X 1*
Cleanable
21
(1) 20 X 25 X 1*
Cleanable
* Factory-provided with furnace.
Fig. 12—Filter Arrangement
A99021
WASHABLE
FILTER
FILTER
SUPPORT
FILTER
RETAINER
17
1
⁄
2
-IN. WIDE
CASINGS ONLY:
INSTALL FIELD-SUPPLIED
FILTER FILLER STRIP
UNDER FILTER.
1
″
24
1
/
2
″
3
″
TABLE 4—MAXIMUM CAPACITY OF PIPE*
NOMINAL
IRON
PIPE
SIZE
(IN.)
INTERNAL
DIAMETER
(IN.)
LENGTH OF PIPE (FT)
10
20
30
40
50
1/2
0.622
175
120
97
82
73
3/4
0.824
360
250
200
170
151
1
1.049
680
465
375
320
285
1-1/4
1.380
1400
950
770
660
580
1-1/2
1.610
2100
1460
1180
990
900
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-in. wc) or less, and
a pressure drop of 0.5-in. wc (based on a 0.60 specific gravity gas).
Ref: Table 10-2 NFPA 54-1996.
—11—
Summary of Contents for 351DAS
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