37
NOTE:
Both readings may be taken simultaneously and read directly on the manometer if so desired. If an air conditioner coil
or Electronic Air Cleaner is used in conjunction with the furnace, the readings must also include these components, as shown
in the following drawing.
4. Consult proper tables for the quantity of air.
If the total external static pressure exceeds the maximum
listed on the furnace rating plate, check for closed dampers,
registers, undersized and/or oversized poorly laid out duct
work.
The temperature rise of the furnace must be within the tem-
perature rise range listed on the furnace rating plate.
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, bend 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 folded open. 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 supply air
plenum. 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 sealed
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.
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. Fil-
ters 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.
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 41
E
DGES
OF
SHEET
METAL
HOLES
MAY
BE
SHARP
. U
SE
GLOVES
AS
A
PRECAUTION
WHEN
REMOVING
SHEET
METAL
FROM
RETURN
AIR
OPENINGS
.
WARNING
Model
Minimum Recommended Filter Size^
*MVM970603BN*
1 - 16 X 25 Side or Bottom
*MVM970803BN*
1 - 16 X 25 Side or Bottom
*MVM970804CN*
1 - 16 X 25 Side or Bottom
*MVM971005CN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
*MVM971205DN*
1 - 20 X 25 Bottom / 2 - 16 X 25 Side Return
*CVM970603BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CVM970803BN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CVM970804CN*
2 - 10 X 20 or 1 - 16 X 25 Top Return
*CVM971005CN*
2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Other s i ze fil ters of equa l or grea ter di mens i ons ma y be us ed, fi l ters
ma y a l s o be centra l ly l ocated
Filter Sizing Chart
