PG96MSA: 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
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
Refer to the instructions supplied with Media Cabinet or accessory air
filter for assembly and other 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.
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.
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