16
SYSTEM OPERATION
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 theses 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
temperature rise range listed on the furnace rating plate.
CUTAWAY OF DUCTWORK
TO EXPOSE COIL
DIGITAL
MANOMETER
RETURN
AIR
Mode
.
SUPPLY
AIR
Checking Static Pressure
(80% Furnace Shown, 90% Similar)
Figure 11
WARNING
Edges of sheet metal 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 12
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
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 air stream. 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.
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.