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3− Both supply and return air plenums shall be square and
least 18" long. They should be the same dimension as
the furnace opening.
4− If unit is installed in a confined space such as a utility
room where there is no complete return air duct sys-
tem, a return air connection should be run (the same
size as the return air opening) to a location outside the
room containing the furnace.
5− Install supply and return air ducts as desired.
Optional Filter Kit
An Optional filter kit is available for OHR23 units. Kit 35K05
is used with OHR23−105/120 units, and kit 35K06 is used
with OHR23−140/154 units. All kits include the following:
2 filters
3 rods
7 screws
1 rack assembly
1 panel
OHR23−140/154 Filter Rack Installation
1− Slide filter rack over return duct flanges.
2− Using a scriber through the filter rack mounting holes,
mark seven mounting hole locations in the return end
of the cabinet. See figure 4.
3− Remove filter rack and drill 1/8" diameter holes at the
marked positions.
4− Place filter rack in position again and secure it to the
cabinet using the sheet metal screws provided. Clear-
ance for the screw driver is provided in outside holes of
rack and in filter support angles.
5− Bend the ends of filter rods and hook ends through
holes provided in top and bottom filter support angles.
6− Slide filter between the support angles and the plenum
side for the filter rack. The filter rods hold the filter in
place.
Figure 4
FILTER
RACK
(Furnished)
FILTER
(Furnished)
RETURN
AIR DUCT
(Not Furnished
by Lennox)
OPENING
IN UNIT
(Either Side)
14
(356)
22
(559)
OHR23 105/120 Optional Filter Kit
