33
E
DGES
OF
SHEET
METAL
HOLES
MAY
BE
SHARP
. U
SE
GLOVES
AS
A
PRECAUTION
WHEN
REMOVING
SHEET
METAL
FROM
RETURN
AIR
OPENINGS
.
WARNING
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 cor-
ners 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 recom
-
mended 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 37
Filters - Read This Section Before Installing The
Return Air Duct work
Filters must be used with this furnace. Discuss filter mainte
-
nance 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 un-
dersized opening will cause reduced airflow.
Refer to the following table to determine filter area re
-
quirements.
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 distribu
-
tion 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” W.C. In some installations
the minimum filter size required will not lend itself to a
filter installation on the side of the furnace. The installation
of a centrally installed air cleaner cabinet or a return duct
filter installation may offer more practicality.
