31
Checking Static Pressure
(80% Furnace Shown, 90% Similar
Figure 42
B
OTTOM
R
ETURN
A
IR
O
PENING
[U
PFLOW
M
ODELS
]
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 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.
When the furnace is heating, the temperature of the return
air entering the furnace must be between 55°F and 100°F.
E
DGES
OF
SHEET
METAL
HOLES
MAY
BE
SHARP
. U
SE
GLOVES
AS
A
PRECAUTION
WHEN
REMOVING
SHEET
METAL
FROM
RETURN
AIR
OPENINGS
.
WARNING
F
ILTERS
- R
EAD
T
HIS
S
ECTION
B
EFORE
I
NSTALLING
T
HE
R
ETURN
A
IR
D
UCT
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.
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 43
Refer to the following table to determine filter area
requirements.
Model
Minimum Recommended Filter Size^
DM96VC0403BN*
1 - 16 X 25 Side or Bottom
DM96VC0603BN*
1 - 16 X 25 Side or Bottom
DM96VC0803BN*
1 - 16 X 25 Side or Bottom
DM96VC0804CN*
1 - 16 X 25 Side or Bottom
DM96VC1005CN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
DM96VC1005DN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
DM96VC1205DN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
DC96VC0403BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
DC96VC0603BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
DC96VC0804CN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
DC96VC1005CN*
2 - 14 X 20 or 1 - 20 X 25 Top Return
DC96VC1205DN*
2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Larger filters may be used, filters may also be centrally located
