TYPICAL MOUNTING POSITIONS
AIR FLOW
Figure 5
BASEMENT FURNACE
(LOWBOY)
Filter is mounted horizontally
in return plenum, just above
furnace.
AIR FLOW
Figure 7
HIGHBOY FURNACE
Side installation. Filter is
mounted vertically, where
return air enters side inlet of
furnace.
LESS THAN
7 INCHES
Figure 9
OFFSET INSTALLATION
Typical use of duct offset to match air fi lter opening.
If duct connection to furnace allows less than nine
inches for mounting the air fi lter, shorten the lateral
trunk, or attach an offset fi tting to the elbow.
OFFSET
AT LEAST
9 INCHES
5
AIR FLOW
Figure 6
COUNTERFLOW
FURNACE
Filter is mounted horizontally
in return duct or plenum, just
above furnace.
Figure 8
HIGHBOY FURNACE
Installation beneath furnace.
Filter mounts horizontally,
where return air enters from
below. Raise furnace and
install beneath base.
AIR FLOW
Figure 10
HORIZONTAL FURNACE
Filter is mounted vertically in the return duct
near furnace.