20
441 01 5003 01
Specifications are subject to change without notice
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 air grille. Any
blower moving a high volume of air will produce audible noise which
could be objectionable when the furnace 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.
•
Refer to furnace
Technical Support Manual
(Blower Data) for
air flow information.
•
Size ductwork to handle air flow for heating (and air
conditioning if so equipped).
Duct Installation Requirements
•
When a furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside of the space
containing the furnace, the return air shall also be handled by
duct(s) sealed to the furnace casing and terminating outside
the space containing the furnace.
CARBON MONOXIDE POISONING HAZARD.
Failure to follow warning could result in personal
injury or death.
Install cooling coil on furnace discharge. Cool air
passing over heat exchanger could cause
condensate to form resulting in heat exchanger
failure.
!
•
When the furnace is used with a cooling unit, the furnace shall
be installed parallel with or on the upstream side of the cooling
unit to avoid condensation in the heating element.
•
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 furnace. Chilled air going through the
furnace could cause condensation and shorten furnace life.
Dampers (purchased locally) can be either automatic or
manual. Manually or automatically operated dampers
MUST
be equipped with a means to prevent furnace and air
conditioning operation, unless damper is in the full heat or cool
position.
•
Installation of locking-type dampers are recommended in all
branches, or in individual ducts to balance system’s air flow.
•
Non--combustible,
flexible
duct
connections
are
recommended for return and supply connections to furnace.
•
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.
•
Ductwork installed in attic, or exposed to outside temperatures
requires a minimum of 2
″
of insulation with outdoor type vapor
barrier.
•
Ductwork installed in an indoor unconditioned space requires a
minimum of 1
″
of insulation with indoor type vapor barrier.
Inspection Panel on some models
For a furnace not equipped with a cooling coil, the outlet duct shall
be provided with a removable access panel. This opening shall be
accessible when the furnace is installed and shall be of such a size
that the heat exchanger can be viewed for possible openings using
light assistance or a probe can be inserted for sampling the air
stream. This access cover shall be attached in such a manner as
to prevent air leaks.
Filters
A filter MUST be used.
A high--velocity filter(s) and rack(s) is supplied with these furnaces.
See
Table 4
for required high--velocity filter sizes.
Table 4
High--Velocity Air Filter Sizes
(max. 600 FPM)
Cabinet
Width
Internal Filter
External Filter Rack
Bottom
Bottom
Side+
15
1
/
2
″
(39 cm)
14
″
X25
″
(36 cm X 64 cm)
14
″
X25
″
14
″
X25
″
or 16
″
X25
″
19
1
/
2
″
(50 cm)
16
″
X25
″
*
(41 cm X 64 cm)
16
″
X25
″
*
16
″
X25
″
*
22
3
/
4
″
(59 cm)
20
″
X25
″
*
(51 cm X 64 cm)
20
″
X25
″
*
16
″
X25
″
*
* Greater than 1600 CFM requires both (left and right) side return filter
racks in upflow position.
+ Side return air duct(s) is not permitted with horizontal furnace installation.
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 external filter grille.
!
RISK OF REDUCED FURNACE LIFE.
F
ailure to follow this caution may result in
premature furnace component failure.
Use of excessively dirty and/or restrictive air filters
may increase furnace operating temperatures and
shorten the life of the furnace.
Filters specified for the furnace are rated at a maximum
of 600 FPM air velocity and sized for the furnace’s
airflow rate. Replacement filters must be of equivalent
type, size, and rating except as described below.
Disposable, low--velocity filters may be used to replace
washable, high--velocity filters, providing they are sized
for 300 FPM or less.
CAUTION
•
The furnaces with 1600 or less CFM rating use a 16” x 25”
high--velocity filter. On these models the filter may be
mounted internally for bottom return or a filter and rack may
be mounted externally for bottom return.
•
The furnaces with greater than 1600 CFM may require that
both (left and right) side returns are used. Two side return
filters and racks are required. Filter racks must be mounted
externally. See
Figure 22.
•
If return air must be on one side only, an optional 20
″
x 25
″
filter standoff rack kit can be used. (See
Figure 20.)
For
bottom return, an internal filter can be used or a filter rack kit
can be mounted externally (NAHA001TK).
•
See
Circulator Air Blower Data
for additional data.
NOTE:
The 20
″
x 25
″
(51 cm X 64 cm) standoff side filter rack gives
more filter area but does not provide more air. See
Figure 20.
To
achieve 2000 CFM 2 side returns are still needed. See
Figure 22.
NOTE:
Disposable low--velocity filters may be replaced with
washable, high--velocity filters. Washable, high--velocity filters can
be replaced
ONLY
with same type and size filter unless
low--velocity filters meet the minimum size areas for 300 FPM or
less.
