Filters; Duct System - Lennox SLP98DFV Installation Instructions Manual

PROPERLY
SIZED FLOOR
OPENING
FIGURE 10
Return Air Opening -- Downflow Units
Return air may be brought in only through the top opening
of a furnace installed in the downflow position. The follow-
ing steps should be taken when installing plenum:
1 - Bottom edge of plenum should be flanged with a
hemmed edge (See figure 11 or 12).
2 - Sealing strips should be used to ensure an airtight
seal between the cabinet and the plenum.
3 - In all cases, plenum should be secured to top of
furnace using sheet metal screws.
4 - Make certain that an adequate seal is made.
PLENUM
(Field Provided)
SEALING STRIP
(Field Provided)
Side View
FIGURE 11
PLENUM
(Field Provided)
SECURE FROM
INSIDE CABINET Side View
FIGURE 12
FURNACE
COOLING COIL
PLENUM
SECURE FROM
OUTSIDE CABINET
CABINET
SIDE PANEL
SEALING STRIP
(Field Provided)
CABINET
SIDE PANEL
Page 9

Filters

This unit is not equipped with a filter or rack. A field-provid-
ed filter is required for the unit to operate properly. Table 3
lists recommended filter size.
A filter must be in place whenever the unit is operating.
IMPORTANT
If a highefficiency filter is being installed as part of this
system to ensure better indoor air quality, the filter must
be properly sized. Highefficiency filters have a higher
static pressure drop than standardefficiency glass/foam
filters. If the pressure drop is too great, system capacity
and performance may be reduced. The pressure drop
may also cause the limit to trip more frequently during
the winter and the indoor coil to freeze in the summer,
resulting in an increase in the number of service calls.
Before using any filter with this system, check the
specifications provided by the filter manufacturer against
the data given in the appropriate Lennox Product
Specifications bulletin. Additional information is provided
in Service and Application Note ACC002 (August 2000).
TABLE 3
Furnace Cabinet Width
B Cabinet 17-1/2"
C Cabinet 21-1/2"

Duct System

Use industry-approved standards to size and install the
supply and return air duct system. This will result in a quiet
and low-static system that has uniform air distribution.
NOTE - Operation of this furnace in heating mode (indoor
blower operating at selected heating speed) with an ex-
ternal static pressure which exceeds 0.8 inches w.c. may
result in erratic limit operation.
Return Air Plenum
Return air must not be drawn from a room where this
furnace, or any other gas-fueled appliance (i.e., water
heater), or carbon monoxide-producing device (i.e.,
wood fireplace) is installed. When return air is drawn
from a room, a negative pressure is created in the room. If
a gas appliance is operating in a room with negative pres-
sure, the flue products can be pulled back down the vent
pipe and into the room. This reverse flow of the flue gas
may result in incomplete combustion and the formation of
carbon monoxide gas. This toxic gas might then be dis-
tributed throughout the house by the furnace duct system.
Use fiberglass sealing strips, caulking, or equivalent seal-
ing method between the plenum and the furnace cabinet
to ensure a tight seal. If a filter is installed, size the return
air duct to fit the filter frame.
Fillter Size
16 X 25 X 1 (1)