PG92MSA: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
19
A10491
Fig. 25 – Installation on Combustible Flooring
FILTER ARRANGEMENT
TIP 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.
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.
The optional media cabinet is sized for bottom return applications for
use in upflow, downflow and horizontal applications. A 16-in. (406 mm)
media cabinet may be used with the 14-3/16-in. (360 mm) furnace and
includes block-off plates.
For upflow side return applications, the optional media cabinet (or field
supplied accessory air cleaner) can be installed on the side of the furnace
or side and bottom when a bottom plenum is used. See Fig. 26 and
Fig. 21.
For downflow applications, the optional media cabinet (or field supplied
accessory air cleaner) must only be connected to the bottom opening on
the furnace. See Fig. 26 and Fig. 22.
For horizontal applications, the optional media cabinet (or field supplied
accessory air cleaner) for all models can be connected to the bottom
opening on the furnace. For side return use in the horizontal position,
refer to Fig. 23. If both side and bottom openings are used in Fig. 23,
each opening used will require an optional filter.
The optional media cabinet (or field supplied accessory air cleaner) can
also be installed in the common return duct prior to entering the return
air opening in any orientation.
Refer to the instructions supplied with Media Cabinet or accessory air
filter for assembly and other details. See Table 7 for filter size details.
Filter and Return Duct Sizing
Pressure drop must be taken into account when sizing filters, filter racks,
IAQ devices, and associated system ductwork. See Table 7 for a
comparison of Pressure Drop (initial/clean resistance to airflow) versus
Airflow for a variety of filter media types and sizes. These are
representative numbers. Consult the filter or IAQ device manufacturers’
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. (FROM A1M96)
TIP 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.
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.
WARNING
!
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in fire, personal injury or
death.
Never operate a furnace without a filter or filtration device installed.
Never operate a furnace with filter or filtration device access doors
removed.
PLENUM
OPENING
C
A
B
D
FLOOR
OPENING
DOWNFLOW
SUBBASE
SHEET METAL
PLENUM
FLOOR
OPENING
FURNACE
(OR COIL CASING
WHEN USED)
COMBUSTIBLE
FLOORING
APPROVED
COIL ASSEMBLY
OR
COIL BOX
FURNACE
SHEET METAL
PLENUM
FLOOR
OPENING
COMBUSTIBLE
FLOORING
NOTICE
!
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.
Table 7 – Filter Media Pressure Drop (Clean) Versus Airflow - in. w.c. (Pa)
14 x 25 Filter
(356 x 635 mm)
Factory-Accessory
Washable
Factory-Accessory
Media
*
Representative After-Market Filter Media
*
Fiberglass
*
Pleated
*
CFM L/s (1-in. / 2.5 cm) (4-in. / 10 cm) (1-in. / 2.5 cm) (2-in. / 5 cm) (1-in. / 2.5 cm) (2-in. / 5 cm)
600 (283) 0.04 (12) 0.05 (12) 0.07 (17) 0.10 (26) 0.24 (60) 0.16 (40)
800 (378) 0.06 (15) 0.07 (19) 0.10 (25) 0.15 (39) 0.34 (85) 0.23 (59)
1000 (472) 0.07 (18) 0.10 (27) 0.13 (34) 0.21 (52) - - 0.32 (81)
1200 (566) 0.08 (20) 0.14 (36) 0.17 (43) 0.27 (68) - - - -
16 x 25 Filter
(406 x 635 mm)
Factory-Accessory
Washable
Factory-Accessory
Media
*
Representative After-Market Filter Media
*
Fiberglass
*
Pleated
*
CFM L/s (1-in. / 2.5 cm) (4-in. / 10 cm) (1-in. / 2.5 cm) (2-in. / 5 cm) (1-in. / 2.5 cm) (2-in. / 5 cm)
600 (283) 0.04 (10) 0.05 (13) 0.06 (15) 0.09 (22) 0.20 (51) 0.13 (34)
800 (378) 0.05 (13) 0.07 (18) 0.08 (21) 0.13 (32) 0.29 (72) 0.20 (49)
1000 (472) 0.06 (16) 0.11 (28) 0.11 (28) 0.17 (43) - - 0.27 (67)
1200 (566) 0.07 (18) 0.15 (37) 0.14 (36) 0.22 (56) - - - -
1400 (661) 0.08 (21) 0.19 (48) 0.18 (45) 0.28 (70) - - - -
1600 (755) 0.09 (23) 0.24 (60) 0.21 (54) - - - - - -
1800 (850) 0.10 (25) - - 0.26 (64) - - - - - -
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