31
WARNING
Edges of sheet metal holes 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.
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 47
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 condensation
in the heating element. With a parallel flow arrangement,
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.
NOTE: In a horizontal installation the air
conditioning coil must be adequately supported
by proper brackets and supports. Inadequate coil
support can result in furnace cabinet distortion
and air leakage.
When the furnace is heating, the temperature of the return
air entering the furnace must be between 55°F and 100°F.
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 Filter Sizing Chart to determine filter area
requirements.
Model
Minimum Recommended Filter Size^
*MVS960603BU
1 - 16 X 25 Side or Bottom
*MVS960805CU
1 - 20 X 25 Bottom/2 - 16 X 25 Side Return
Filter Sizing Chart
^ Larger filters may be used, filters may also be centrally located.
Table 9
Change filters before occupants take ownership of a new home!
One of the most common causes of a problem in a forced
air heating system is a blocked or dirty filter. Circulating
air filters must be inspected monthly for dirt accumulation
and replaced if necessary. Failure to maintain clean
filters can cause premature heat exchanger failure. A
new home may require more frequent replacement until
all construction dust and dirt is removed. Circulating air
filters are to be installed in the return air duct external to
the furnace cabinet. 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”
W.C. In some installations the minimum filter size required
(consult filter sizing chart above) 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.
