30
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 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.
E
DGES
OF
SHEET
METAL
HOLES
MAY
BE
SHARP
. U
SE
GLOVES
AS
A
PRECAUTION
WHEN
REMOVING
SHEET
METAL
FROM
RETURN
AIR
OPENINGS
.
WARNING
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 40
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 pre-
vent chilled air from entering the furnace and, if manually oper-
ated, 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 opera-
tion.
When the furnace is heating, the temperature of the return air
entering the furnace must be between 55°F and 100°F.
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 mainte-
nance with the building owner. Filters do not ship with this fur-
nace, but must be provided, sized and installed externally by the
installer. Filters must comply with UL900 or CAN/ULCS111 stan-
dards. If the furnace is installed without filters, the warranty will
be voided.
On upflow units, guide dimples locate the side return cutout lo-
cations. Use a straight edge to scribe lines connecting the dimples.
Cut out the opening on these lines.
NOTE:
An undersized open-
ing will cause reduced airflow.
Refer to the following table to determine filter area require-
ments.
Model
Minimum Filter Size
*
MVC960403BN
**
20 X 24
*
MVC960603BN
**
20 X 25
*
MVC960803BN
**
18 X 36
*
MVC960804CN
**
24 x 30
*
MVC961005CN
**
24 X 36
*MVC961205DN**
2 (20 X 25)
*
CVC960403BN
**
20 X 24
*
CVC960603BN
**
20 X 25
*
CVC960804CN
**
18 X 36
*
CVC961005CN
**
24 x 30
*
CVC961205DN
**
2 (20 X 25)
Filter Sizing Chart
[Based on 300 ft/min filter face velocity]
Change filters before occupants take ownership of a new
home!
U
PRIGHT
I
NSTALLATIONS
Depending on the installation and/or customer preference, dif-
fering filter arrangements can be applied. Filters can be in-
stalled in the central return register or a side panel external filter
rack kit (upflows). As an alternative a media air filter or elec-
tronic air cleaner can be used as the requested filter.
The following figure shows possible filter locations.
FI
L
T
E
R
AIR FLOW
CENTRAL
RETURN
GRILLE
FI
L
T
E
R
SIDE RETURN
EXTERNAL FILTER
RACK KIT
(EITHER SIDE)
Possible Upright Upflow
Figure 41
