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Installer's
Guide
®
CONFINED
SPACE
AIR FROM
INSIDE
BUILDING
CONFINED
SPACE
PERMANENT
OPENINGS
_J
®
CONFINED
SPACE
AIR FROM
OUTDOORS
L
CONFINED-
SPACE
CONFINED
SPACE
k
AIR FROM
VENTILATED
ATTIC/CRAWL
SPACE
_
ATTIC
LOUVERS
DOORS
,UTLET
CONFINED
-
AIR
SPACE
ALTERNATE
INLET
INLET
A_R _
AIR DUCT
CONFINED
SPACE
AIR FROM VENTILATED
ATTIC
:LOUVERS
TO OUTDOORS
CONFINED-
SPACE
INLET
AIR
DUCT
DUCT
CONNECTIONS
Air duct
systems
should
be installed
in accordance
with
standards
for air conditioning
systems,
National
Fire
Protection
Association
Pamphlet
No. 90. They
shouM
be sized
in accordance
with
ACCA
Manual
D or whichever
is appli-
cable.
Central
filrnaces,
when
used
in connection
with
cooling
units,
shall
be installed
in parallel
or on the
upstream
side
of the
cooling
coil to avoid
condensation
in the
heat
exchanger.
With
a parallel
flow arrangement,
the dampers
or other
means
used
to control
flow of air shall
be adequate
to prevent
chilled
air from
entering
the fllrnace,
and
if manually
operated,
must
be equipped
with
means
to prevent
operation
of either
unit
unless
the damper
is in fifll heat
or cool position.
On any job, flexible
connections
of nonflammable
material
may
be used Ibr return
air and discharge
connections
to prevent
transmission
of vibration.
Though
these
units
have
t_en
spe-
cifically
designed
_br quiet,
vibration
free operation,
air ducts
can act as sounding
boards
and could,
if poorly
installed,
am-
plil_¢ the slightest
vibration
to the annoyance
level.
When
the
filrnace
is located
in a utility
room
adjacent
to the
living
area,
the system
should
be carefiflly
designed
with
returns
to minimize
noise
transmission
through
the return
air grille.
Although
these
filrnaces
are designed
with
large
blowers
operating
at moderate
speeds,
any blower
moving
a
high
w)lume
of air will produce
audible
noise
which
could
be
objectionable
when
the
unit
is located
very
close to a living
area.
It is often
advisable
to route
the return
air ducts
under
the
floor or through
the attic.
Such
design
permits
the
installation
of air return
remote
from
the living
area
(i.e. central
hall).
When the fllrnace
is installed
so that the supply ducts carry
air circulated
by the furnace to areas
outside the space
containing
the fllrnace,
the return
air shall also be handled
by
a duct(s) sealed to the furnace
and terminating
outside
the
space containing
the furnace.
RETURN AIR DUCT SYSTEMS
Where
there
is no complete
return
duct
system,
the
return
connection
must
be run full size from
the fur-
nace to a location
outside
the utility
room,
basement,
attic,
or crawl
space.
Do Not install
return
air through
the back of the Iumace
cabinet
Do Not install
return
air through
the side of the filrnace
cabinet
on horizontal
applications.
NOTE:
Minimum return air temperature is 50 ° F.
All return
air duct
systems
should
provide
fl)r installation
of
return
air filters.
1. Set the fllrnace
in place.
2. For upflow
side return
installations,
remove
the insulation
around
the opening
in the blower
compartment.
3. The side panels
of the upflow
furnace
include
locating
notches
that
are used
as guides
for cutting
an opening
Ior
return
air, refer
m Figure
10 and the outline
drawing
on
page
4 lbr duct
connection
dimensions
for various
furnaces.
NOTE:
On upflow
5 ton airflow
models,
if the airflow
requirement
exceeds
1800 CFM, these models
will require
return
air
openings
and filters on both sides;
OR I side and the
bottom;
OR just the bottom.
8
18-CD19D6-27
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