26
XIII. CIRCULATING AIR & FILTERS
D
UCTWORK
- A
IR
F
LOW
Duct systems and register sizes must be properly designed for the
CFM and external static pressure rating of the furnace. Ductwork
should be designed in accordance with the recommended meth-
ods of “Air Conditioning Contractors of America” Manual D.
A duct system must be installed in accordance with Standards of
the National Board of Fire Underwriters for the Installation of Air
Conditioning, Warm Air Heating and Ventilating Systems. Pam-
phlets No. 90A and 90B.
A closed return duct system must be used, with the return duct
connected to the furnace. NOTE: Ductwork must never be attached
to the back of the furnace.
Supply and return connections to the
furnace may be made with flexible joints to reduce noise transmis-
sion. To prevent the blower from interfering with combustion air or
draft when a central return is used, a connecting duct must be
installed between the unit and the utility room wall. A room, closet,
or alcove must not be used as a return air chamber.
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 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 operation.
When the furnace is heating, the temperature of the return air en-
tering 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
UCTWORK
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 by the installer. Filters must comply with UL900
or CAN/ULCS111 standards. If the furnace is installed without fil-
ters, the warranty will be voided.
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 Minimum Filter Area tables to determine filter area require-
ments.
600
800
1000
1200
1400
1600
2000
0453BXA
194*
194*
240
288
---
---
---
0703BXA
---
324*
324*
324*
336
---
---
0704CXA
---
---
291*
291*
336
384
---
0904CXA
---
---
432*
432*
432*
432*
---
0905DXA
---
---
---
388*
388*
388*
480
1155DXA
---
---
---
486*
486*
486*
486*
In
p
u
t_
_
A
ir
fl
o
w
COOLING AIRFLOW REQUIREMENT (CFM)
*Minimum filter area dictated by heating airflow requirement.
Permanent Minimum Filter Area (sq. in)
[Based on a 600 ft/min filter face velocity]
600
800
1000
1200
1400
1600
2000
0453B XA
388*
388*
480
576
---
---
---
0703B XA
---
647*
647*
647*
672
---
---
0704CXA
---
---
583*
583*
672
768
---
0904CXA
---
---
863*
863*
863*
863*
---
0905DXA
---
---
---
777*
777*
777*
960
1155DXA
---
---
---
971*
971*
971*
971*
In
p
u
t_
_
A
ir
fl
o
w
COO LING AIRFLO W REQ UIREM ENT (CFM )
*Minimum filter area dictated by heating airflow requirement.
Disposable Minimum Filter area (sq. in)
[Based on 300 ft/min filter face velocity]
U
PRIGHT
I
NSTALLATIONS
Depending on the installation and/or customer preference, differ-
ing filter arrangements can be applied. Filters can be installed in
the central return register or a side panel external filter rack kit
(upflows). As an alternative a media air filter or electronic air cleaner
can be used as the requested filter.
The following figure shows possible filter locations.
F
IL
T
E
R
AIR FLOW
CENTRAL
RETURN
GRILLE
F
IL
T
E
R
SIDE RETURN
EXTERNAL FILTER
RACK KIT
(EITHER SIDE)
FIL
TE
R
F
IL
T
E
R
AIR FLOW
FILTER
ACCESS
DOOR
CENTRAL
RETURN
GRILLE
RETURN
DUCT
FI
LT
E
R
FILTER
SUPPORT
BRACKET
(PROVIDED)
Possible Upright Upflow
Possible Upright Counterflow
Filter Locations
NOTE: Internal filter retention is not provided on this furnace. If an
internal installation is desired, an internal filter retention kit is avail-
able as an accessory. Please see your distributor for details.
