440 01 1024 01
Specifications are subject to change without notice
39
8. Ductwork and Filter
CARBON MONOXIDE POISONING HAZARD.
Failure to follow this warning could result in
personal injury or death.
Do NOT draw return air from inside a closet or utility
room where furnace is located. Return air duct
MUST be sealed to furnace casing.
!
WARNING
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
recommended 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 going
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 death
or personal injury.
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 or downflow
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
″
filter , cut out the
embossed area shown in
Figure 42
. This will provide a
14
1
/
2
″
x 22
1
/
2
″
approximate opening.
Figure 42
Side Return Air Cutout
Embossed Area
on Side of Furnace
A = 14
1
/
2
″
Height of Cutout for 16
″
x 25
″
Filter
B = 22
1
/
2
″
Width of Cutout for 16
″
x 25
″
Filter
A
Furnace
Bottom
B
NOTE: Furnaces with 5 ton cooling rating may require both
(left and right) side return or one side and bottom return (see
notes in Circulation Air Blower Data). Side return air duct(s) is
not permitted with horizontal or downflow furnace
installation.
2. Bottom returns can be made by removing the knockout
panel in the furnace base. Do
NOT
remove knock-out
except 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
recommended 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 reduce
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
″
insulation and
vapor barrier.
2. Insulate ductwork in indoor unconditioned areas with a
minimum of 1
″
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:
•
Washable, high velocity filters are based on a maximum
air flow rating of 600 FPM.
•
Disposable, low velocity filters are based on a maximum
air flow of 300 FPM when used with filter grille.
•
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.
