30
WARNING
Edges of sheet metal hole may be sharp. Use gloves as a
precaution when removing sheet metal from return air
openings.
Bottom Return Air Opening
[Upflow Models]
The bottom return air opening on upflow models utilizes
a “lance and cut” method to remove sheet metal from the
duct opening in the base pan. To remove, simply press
out the lanced sections by hand to expose the metal strips
retaining the sheet metal over the duct opening. Using
tin snips, cut the metal strips and remove the sheet metal
covering the duct opening. In the corners of the opening,
cut the sheet metal along the scribe lines to free the duct
flanges. Using the scribe line along the duct flange as a
guide, unfold the duct flanges around the perimeter of the
opening using a pair of seamer pliers or seamer tongs.
NOTE: Airflow area will be reduced by
approximately 18% if duct flanges are not
unfolded. This could cause performance issues
and noise issues.
When the furnace is used in connection with a cooling unit,
the furnace should be installed in parallel with or on the
upstream side of the cooling unit to avoid condensa tion
in the heating element. With a parallel flow arrange ment,
the dampers or other means used to control the flow of
air must be adequate to prevent chilled air from entering
the furnace and, if manually operated, must be equipped
with means to prevent operation of either unit unless the
damper is in the full heat or cool position.
When the furnace is installed without a cooling coil, it is
recommended that a removable access panel be provided
in the outlet air duct. 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 visual light
inspection or such that a sampling probe can be inserted
into the airstream. The access panel must be made to
prevent air leaks when the furnace is in operation.
When the furnace is heating, the temperature of the return
air entering the furnace must be between 55°F and 100°F.
CUT FOUR CORNERS
AFTER REMOVING SHEET
METAL
CUT USING TIN SNIPS
PRESS OUT BY HAND
SCRIBE LINES OUTLINING
DUCT FLANGES
Duct Flange Cut Outs
Figure 42
Filters - Read This Section Before Installing
The Return Air Duct work
Filters must be used with this furnace. Discuss filter
maintenance with the building owner. Filters do not ship
with this furnace, but must be provided, sized and installed
externally by the installer. Filters must comply with UL900
or CAN/ULCS111 standards. Damage or repairs due to
the installation of the furnace without filters is not covered
under the warranty.
On upflow units, guide dimples locate the side return cutout
locations. Use a straight edge to scribe lines connecting
the dimples. Cut out the opening on these lines.
NOTE: An undersized opening will cause reduced
airflow.
Refer to the following table to determine filter area
requirements.
Model
Minimum Recommended Filter Size^
*MEC960303AN*
1 - 16 X 25 Side or 1- 14 X 25 Bottom
*MEC960403AN*
1 - 16 X 25 Side or 1- 14 X 25 Bottom
*MEC960603AN*
1 - 16 X 25 Side or 1- 14 X 25 Bottom
*MEC960302BN*
1 - 16 X 25 Side or Bottom
*MEC960402BN*
1 - 16 X 25 Side or Bottom
*MEC960603BN*
1 - 16 X 25 Side or Bottom
*MEC960803BN*
1 - 16 X 25 Side or Bottom
*MEC960804CN*
1 - 16 X 25 Side or Bottom
*MEC961004CN*
1 - 16 X 25 Side or Bottom
*MEC961005CN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
*MEC961205DN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
*CEC960403BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CEC960603BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CEC960803BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CEC961005CN*
2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Larger filters may be used, filters may also be centrally located
Change filters before occupants take ownership of a
new home!
Upright Installations
Depending on the installation and/or customer preference,
differing filter arrangements can be applied. Filters can
be installed in the central return register or a side panel
external filter rack kit (upflows). As an alternative a media
air filter or electronic air cleaner can be used as the
requested filter. Consider installing an air cleaner with
deep-pleated media filter at the time of furnace installation.
A deep-pleated filter with a MERV rating of 8 (minimum)
will often provide better filtration to protect equipment and
the air distribution system than a standard 1” filter and
often has lower static pressure loss than a 1” filter. Also
a deep-pleated filter will typically require less frequent
replacement intervals. Avoid using highly restrictive 1”
filters which produce static pressure loss greater than .25”
