39
Installation
NOTE
: Design and install the air distribution system to comply
with Air Conditioning Contractors of America manuals and/or
NFPA pamphlets 90A and 90B or other approved methods that
conform to local codes and good trade practices.
1. When furnace supply ducts carry air outside furnace area,
seal return air duct to furnace casing and terminate duct
outside furnace space.
2. Install air conditioning cooling coil (evaporator) on outlet
side of furnace.
3. For furnaces installed without a cooling coil it is recom-
mended that the outlet duct be provided with a removable
access panel. This panel should be accessible when the
furnace is installed so the exterior of the heat exchanger
can be viewed for inspections. The access panel
MUST
be
sealed to prevent leaks.
4. If separate evaporator and blower units are used, install
good sealing dampers for air flow control. Chilled air go-
ing through the furnace could cause condensation and
shorten the furnace life.
NOTE
: Dampers (field supplied) can be either automatic or
manual. Manually operated dampers
MUST
be equipped with a
means to prevent furnace or air conditioning operation unless
damper is in the full heat or cool position.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury or
death.
Cool air passing over heat exchanger can cause condensate to
form resulting in heat exchanger failure.
!
WARNING
Connections
NOTE
: On upflow installations, return air can enter through
either side, both sides, or the bottom. On horizontal installations
the return air must enter through the knockout opening in the
lower panel of the furnace. Return air
can not
enter through rear
of the furnace. When the furnace is located in an area near or
adjacent to the living area, the system should be carefully
designed with returns to minimize noise transmission through the
return grille. Any blower moving a high volume of air will
produce audible noise which could be objectionable to when the
unit is located very close to living areas. It is advisable to route
the return air ducts under the floor or through the attic.
1. For side connections using a 16
″
x 25
″
(406 x 635 mm)
filter, cut out the embossed area shown in Fig. 41. This
will provide a 14
1
/
2
″
x 22
1
/
2
″
(368 x 572 mm) approxim-
ate opening.
NOTE
:
Furnaces with 5 ton cooling rating may require both
(left and right) side return or one side and bottom return.
Side return air duct(s) is not permitted with horizontal
furnace installation.
Embossed Area
on Side of Furnace
A = 14 /
2
″
(368.3mm) Height of Cutout for 16
″
x 25
″
(406.4 x 635mm) Filter
B = 22
1
/
2
″
(571.5mm) Width of Cutout for 16
″
x 25
″
(406.4 x 635mm) Filter
A
Furnace
Bottom
B
A07728
Fig. 41 -- Side Return Air Cutout
2. Bottom returns can be made by removing the knockout
panel in the furnace base. Do
NOT
remove knock-out ex-
cept for a bottom return.
3. Installation of locking-type dampers are recommended in
all branches, or in individual ducts to balance system’s air
flow.
4. Non-combustible, flexible duct connectors are recommen-
ded for return and supply connections to furnace.
5. If air return grille is located close to the fan inlet, install at
least one, 90
°
air turn between fan and inlet grille to re-
duce noise.
NOTE
: To further reduce noise, install acoustical air turning
vanes and/or line the inside of duct with acoustical material.
Sizing
Existing or new ductwork
MUST
be sized to handle the correct
amount of airflow for either heating only or heating and air
conditioning.
Insulation
1. Insulate ductwork installed in attics or other areas exposed
to outside temperatures with a minimum of 2
″
(51 mm)
insulation and vapor barrier.
2. Insulate ductwork in indoor unconditioned areas with a
minimum of 1
″
(25 mm) insulation with indoor type vapor
barrier.
Filters
A Filter
must
be used:
Filters are not supplied with these furnaces, but can be purchased
from the distributor.
Use either filter type:
S
Washable, high velocity filters are based on a maximum
air flow rating of 600 FPM.
S
Disposable, low velocity filters are based on a maxim-
um air flow of 300 FPM when used with filter grille.
S
See
Circulating Air Blower Data
for additional data.
NOTE
: Disposable, low velocity filters may be replaced with
washable, high velocity filter providing they meet the minimum
size areas. Washable, high velocity filters can be replaced
ONLY
with same type and size.
359AA
V
