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935SB: Installation, Start-up, Operating and Service Maintenance Instructions
There are no provisions for an internal filter in these furnaces. An
external filter rack is required and is purchased separately. A field
supplied accessory air cleaner may also be used in place of the filter
rack.
For upflow applications, the filter can be installed on either side of the
furnace, the bottom of the furnace or any combination of side and
bottom of the furnace (see
Fig.
For horizontal applications, the filter rack (or field supplied accessory air
cleaner) can be connected to the bottom opening on the furnace. For side
return use in the horizontal position (see
bottom openings are used (see
filter.
A filter rack or any field supplied accessory air cleaner can also be
installed in the common return duct prior to entering the return air
opening in any orientation.
The furnace may be used with an optional external media filter cabinet.
The optional media filter cabinet uses either a standard 1-in. (25 mm)
filter or 4-in. (102 mm) wide media filter which can be purchased
separately. A field supplied accessory air cleaner may also be used in
place of the media cabinet.
Filter and Return Duct Sizing
Pressure drop must be taken into account when sizing filters, filter racks,
IAQ devices, and associated system ductwork. For a comparison of
Pressure Drop (initial/clean resistance to airflow) versus Airflow for a
variety of filter media types and sizes
representative numbers. Consult the filter or IAQ device manufacturers'
FURNACE CASING WIDTH
†
14-3/16 (360)
17-1/2 (445)
21 (533)
24-1/2 (622)
*. Recommended to maintain air filter face velocity. See Product Data for part number.
†. Not all families have these models.
FURNACE
CASING WIDTH
IN. (mm)
14–3/16
Upflow Applications on Combustible or Noncombustible Flooring
*
(360)
17–1/2
Upflow Applications on Combustible or Noncombustible Flooring
(445)
21
Upflow Applications on Combustible or Noncombustible Flooring
(533)
24-1/2
Upflow Applications on Combustible or Noncombustible Flooring
*
(622)
Not all families have these models.
*.
16 x 25 Filter
Factory-Accessory
(406 x 635 mm)
Washable
CFM
L/s
(1-in. / 2.5 cm)
600
(283)
0.04
800
(378)
0.05
1000
(472)
0.06
1200
(566)
0.07
1400
(661)
0.08
1600
(755)
0.09
1800
(850)
0.10
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
28).
Fig.
29). If both side and
Fig.
29), each opening used will require a
(Table
10). These are
Table 8 – Air Filter Selection and Duct Sizing - In. (mm)
SIDE RETURN
16 x 25 x 3/4 (406 x 635 x 19)
16 x 25 x 3/4 (406 x 635 x 19)
16 x 25 x 3/4 (406 x 635 x 19)
16 x 25 x 3/4 (406 x 635 x 19)
Table 9 – Opening Dimensions - In. (mm)
APPLICATION
(subbase not required)
(subbase not required)
(subbase not required)
(subbase not required)
Table 10 – Filter Media Pressure Drop (Clean) Versus Airflow - in. w.c. (Pa)
Factory-Accessory
Media*
(4-in. / 10 cm)
(10)
0.05
(13)
(13)
0.07
(18)
(16)
0.11
(28)
(18)
0.15
(37)
(21)
0.19
(48)
(23)
0.24
(60)
(25)
-
specification sheet for performance data for a particular filter media or
IAQ device.
Design the filter and associated ductwork for the best match of pressure
drop versus filter size. Best practice usually chooses filter systems with
pressure drops under 0.2 in. w.c. (50 Pa), with the best blower electrical
efficiency and system airflow performance occurring with filter pressure
drops under 0.1 in. w.c. (25 Pa).
Due to the relatively high pressure drops of 1-in. (25 mm) thick
after-market filter media, it is recommended that the filtration system be
designed for at least 2-in. (51 mm) thick media.
TIPS FROM CONTRACTORS: Install a media cabinet capable of
incorporating a 4-in. (102 mm) thick media filter. This allows room for
future upgrades to other IAQ devices.
Design the duct system FIRST to determine how much pressure drop
may be allowed in the filter system. See the Air Ducts section.
Excessive filter pressure drop often compromises system airflow and
duct performance, causes inadequate airflow to the furthest ends of the
duct system, as well as causes excess noise and higher than anticipated
electrical consumption.
Provide duct transitions, as required, to smoothly transition airflow from
the return duct system to the filter (or IAQ device) to the furnace when
the dimensions of the ductwork or furnace return air opening do not
match the required filter or IAQ device dimensions. See the instructions
supplied with factory-accessory duct adapters.
FILTER SIZE
BOTTOM RETURN
14 x 25 x 3/4 (356 x 635 x 19)
16 x 25 x 3/4 (406 x 635 x 19)
20 x 25 x 3/4 (508 x 635 x 19)
24 x 25 x 3/4 (610 x 635 x 19)
12-11/16
(322)
(406)
19-1/2
(495)
(584)
Representative After-Market Filter Media*
Fiberglass*
(1-in. / 2.5 cm)
(2-in. / 5 cm)
0.06
(15)
0.09
0.08
(21)
0.13
0.11
(28)
0.17
0.14
(36)
0.22
0.18
(45)
0.28
0.21
(54)
-
0.26
(64)
21
NOTICE
!
PLENUM OPENING
A
B
21-5/8
13-5/16
(549)
16
21-5/8
16-5/8
(549)
21-5/8
20-1/8
(549)
23
21-1/8
23-5/8
(537)
(1-in. / 2.5 cm)
(22)
0.20
(51)
(32)
0.29
(72)
(43)
-
(56)
-
(70)
-
-
-
-
-
-
-
*
FILTER TYPE
Washable
Washable
Washable
Washable
FLOOR OPENING
C
D
22-1/4
(338)
(565)
22-1/4
(422)
(565)
22-1/4
(511)
(565)
22-1/4
(600)
(565)
Pleated*
(2-in. / 5 cm)
0.13
(34)
0.20
(49)
-
0.27
(67)
-
-
-
-
-
-
-
-
-
-
-
-
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