41
440 01 1051 02
Specifications are subject to change without notice.
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.
Figure 42
Side Return Air Cutout
Embossed Area
on Side of Furnace
A
Furnace
Bottom
B
A = 14
1
/
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
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.
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
″
(50.8mm)
insulation and vapor barrier.
2. Insulate ductwork in indoor unconditioned areas with a
minimum of 1
″
(25.4mm) 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.
Figure 43
Side Mounted Filter Rack
25-20-90
Filter Installation using Optional Filter Rack
When installing or removing a bottom mounted filter, slide the two
side filter clips to the back of the furnace
BEFORE
installing or
removing. This will allow the filter to clear the front raised edge of
the furnace. Insert filter into side clips first and push filter back until
it is fully engaged into back clip. When filter is in place, slide clips
back into place midway on filter as shown in
Figure 44
and
Figure 45.
Figure 44
Bottom Mounted Filter Rack
Slide filter clips towards back before removing
25-24-18-1
Center Clip
side-to-side
9
″
(152.4mm)
Figure 45
Filter Clip Construction
3
″
1
1
/
4
″
1
1
/
2
″
11
/
16
″
26 Ga. Galvanized Steel
FAST part number 1008482
(38.1)
(31.8)
(76.2)
(27)
Refer to
Figure 46
and for guidelines to install filters. Furnaces
which require larger filter media and have limited clearances on
one side of furnace, require a standoff filter rack, see
Figure 46
,
available from your distributor.
