Carrier 59MN7B Installation, Start-Up, Operating And Service And Maintenance Instructions page 23

Roll- - Out Protection
Provide a minimum 12- -in. x 22- -in. (305 x 559 mm) piece of
sheet metal for flame roll- -out protection in front of burner area for
furnaces closer than 12- -in. (305 mm) above the combustible deck
or suspended furnaces closer than 12- -in. (305 mm) to joists. The
sheet metal MUST extend underneath the furnace casing by 1- -in.
(25 mm) with the door removed.
The bottom closure panel on furnaces of widths 17- -1/2- -in. (445
mm) and larger may be used for flame roll- -out protection when
bottom of furnace is used for return air connection. See Fig. 28 for
proper orientation of roll- -out shield.
Supply Air Connections
For a furnace not equipped with a cooling coil, the outlet duct
shall be provided with a removable access panel. 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 possible
openings using light assistance or a probe can be inserted for
sampling the air stream. The cover attachment shall prevent leaks.
Connect supply- -air duct to flanges on furnace supply- -air outlet.
Bend flange upward to 90_ with wide duct pliers. See Fig. 19. The
supply- -air duct must be connected to ONLY the furnace
supply- -outlet- -air duct flanges or air conditioning coil casing
(when used). DO NOT cut main furnace casing side to attach
supply air duct, humidifier, or other accessories. All accessories
MUST be connected to duct external to furnace main casing.
Return Air Connections
The return- -air duct may be connected to bottom of the furnace.
The side of casing that faces downward may also be used for
return air connection. A combination of the bottom and
downward facing side may also be used. The upward facing side
of the casing cannot be used as a return air connection. See Fig.
25.
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return- -air opening. Remove this panel when bottom return
air is used. This panel may be used as a roll- -out shield or discard.
To remove bottom closure panel, see Fig. 20 or 21.
Side Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return- -air opening. This panel MUST be in place when
side return air inlet(s) are used without a bottom return air inlet.
Not all horizontal furnaces are approved for side return air
connections. See Fig. 25. Where required by code, seal bottom
closure to furnace with tape, mastic or other durable sealing
method.
Filter Arrangement
WARNING
!
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in fire, personal
injury or death.
Never operate a furnace without a filter or filtration device
installed. Never operate a furnace with filter or filtration
device access doors removed.
The furnace is shipped with a factory-supplied Media Filter
Cabinet. The Media Filter Cabinet uses either a standard 1- -in. (25
mm) filter or 4- -in. (102 mm) wide Media Filter which can be
purchased separately. A field supplied accessory air cleaner may
also be used in place of the media cabinet.
The Media Cabinet is sized for bottom return applications for use
in upflow, downflow and horizontal applications. A 16- -inch (406
mm) Media Cabinet is shipped with the 14- -3/16-in. (360 mm)
furnace and includes block-off plates.
For upflow side return applications, the Media Cabinet (or field
supplied accessory air cleaner) can be installed on the side of the
furnace or side and bottom when a bottom plenum is used. See
Fig. 23 and 26.
For downflow applications, the Media Cabinet (or field supplied
accessory air cleaner) must only be connected to the bottom
opening on the furnace. See Fig. 24 and 26.
For horizontal applications, the Media Cabinet (or field supplied
accessory air cleaner) for all models can be connected to the
bottom opening on the furnace. For side return use in the
horizontal position, refer to Fig. 25. If both side and bottom
openings are used in Fig. 25, each opening used will require a
filter.
The media cabinet (or field supplied accessory air cleaner) can also
be installed in the common return duct prior to entering the return
air opening in any orientation.
FURNACE
CASING
SIDE
WIDTH
RETURN
16 x 25 x 3/4
17---1/2
(406 x 635 x
(445)
19)
16 x 25 x 3/4
21 (533) (406 x 635 x
19)
16 x 25 x 3/4
24---1/2
(406 x 635 x
(622)
19)
* Recommended to maintain air filter face velocity. See Product Data for
part number.
Refer to the instructions supplied with Media Cabinet or accessory
air filter for assembly and other details. See Table 5 for filter size
details.
Filter and Return Duct Sizing
Pressure drop must be taken into account when sizing filters, filter
racks, IAQ devices, and associated system ductwork. See Table 5
for a comparison of Pressure Drop (initial/clean resistance to
airflow) versus Airflow for a variety of filter media types and
sizes. These are representative numbers. Consult the filter or IAQ
device manufacturers' specification sheet for performance data for
a particular filter media or IAQ device.
Design the filter and associated ductwork for the best match of
pressure drop versus filter size. Best practice usually chooses filter
systems with pressure drops under 0.2 in. W.C. (50 Pa), with the
best blower electrical efficiency and system airflow performance
occurring with filter pressure drops under 0.1 in. W.C. (25 Pa).
NOTICE
Design the duct system FIRST to determine how much
pressure drop may be allowed in the filter system. See the Air
Ducts section. Excessive
compromises system airflow and duct performance, causes
inadequate airflow to the furthest ends of the duct system, as
well as causes excess noise and higher than anticipated
electrical consumption.
Provide duct transitions, as required, to smoothly transition airflow
from the return duct system to the filter (or IAQ device) to the
furnace when the dimensions of the ductwork or furnace return air
opening do not match the required filter or IAQ device
dimensions. See the instructions supplied with factory- -accessory
duct adapters.
23
FILTER SIZE
FILTER TYPE
BOTTOM
RETURN
16 x 25 x 3/4
(406 x 635 x Washable*
19)
20 x 25 x 3/4
(508 x 635 x Washable*
19)
24 x 25 x 3/4
(610 x 635 x
Washable*
19)
filter pressure drop often