Instructions / Assembly

Heating and Cooling Essentials
Figure 28-44. Preparing to cut a floor diffuser opening. A—Measure and trace the opening for the diffuser. B—Drill a centered
hole through floor. C—Check clearances from below.
Figure 28-45. installing a floor diffuser. A—Cut along the outline with a jigsaw, circular, or reciprocating saw. B—Secure the
register box (boot) to floor with nails. C—Install the floor diffuser into boot opening and secure it with screws.
28.15 Return Air System - --#
In houses where air can easily circulate to one loca-
tion, a central return air grille is adequate. In two-story
homes or long ranch designs, a more efficient, yet
more expensive system routes air through separate
piping from individual rooms back to the furnace for
retreatment. The system filter or electronic air cleaner
is normally installed where the return air duct attaches
to the furnace, Figure 28-46.
A disposable filter is usually made of fiberglass
within a cardboard frame, Figure 28-47. These filters
should be replaced at regular intervals to avoid
restricted airflow. An arrow printed on the filter frame
.shows direction of airflow.
28.15.1 Return Air Grilles
Return air grilles are nonadj us table, and are not
equipped with dampers. They should permit unre-
stricted ffow of return air back to the furnace. Return
air grilles are available in various sizes. A return air
grill is normally positioned on an inside wall, in a
baseboard on an inside wall, or in the floor next to an
inside wall, Figure 28-48.
Installing Return Air Grilles
When installing wall-type grilles, the floor plate
inside the partition must be cut for passage of return air
to the duct or enclosed joist space below. It is easier if the
Return air
Supply air
Air filter or
electronic cleaner
Figure 28-46. For proper circulation, return air is just as
important as supply air.