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Figure 13. SC038-23A Pressure Switch
1. Shut off any electrical power to the furnace.
2. Label and disconnect the tubing and wires from the
pressure switch (1).
3. Remove two screws (2) securing the pressure switch
(1) to the side of the furnace.
4. Remove two 1/4" black plugs (3) on the opposite side
of the cabinet that the pressure switch will be relocated
to.
5. Position the pressure switch (1) in its new location and
secure it in place using the same screws (2) removed
in step 2
6. Insert the plugs (3) into the holes on the side that the
pressure switch (1) was removed from.
7. Reconnect the tubing and wiring to the pressure switch
(1) being careful that they will not fall into the burner
box.
CAUTION:
It is extremely important that all wires and tubes
be correctly reattached to the pressure switch(s).
Failure to do so will result in malfunction or
compromised safety functions of the furnace.
8. Check the furnace for proper operation as directed in
Startup and Adjustments section. If the furnace shuts
down during the pre-purge, the switch that measures
pressure in the header needs to be checked for correct
tubing connections.
Downflow Furnaces
WARNING:
The furnace must not be installed directly on
carpeting,tile,or any combustible material other
than wood flooring.
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WARNING:
Failure to install the downflow sub-base kit may
result in fire,property damage or personal injury.
To install an *SL & *SM series gas furnace on combustible
flooring, a special sub-base is required. Downflow sub-
base kits are factory supplied accessories and are listed
according to the cabinet letter of the furnace. For 'B', 'C',
and 'D' size cabinets use Kit #904911. Please follow the
instructions provided with the kit.
A downflow sub-base kit is not necessary if the furnace
is installed on a factory or site-built cased air conditioning
coil. However, the plenum attached to the coil casing
must be installed so that its surfaces are at least 1" from
combustible construction.
Installation on a Concrete Slab
1. Create an opening in the floor according to the
dimensions in
Table
3.
2. Position the plenum and the furnace as shown in
Figure
14.
Opening in concrete floor
"B"
Model #
Dim. "A"
054D-24B
072D-24B
072D-35C
090D-35C
118D-45D
120D-45D
NOTE: Dimensions shown in Inches.
Table 3. Cutout Dimensions
Concrete
Floor
Figure 14. Furnace on a Concrete Slab
"A"
Dim. "B"
16 5/8
19 1/4
16 5/8
19 1/4
20 1/8
19 1/4
20 1/8
19 1/4
23 5/8
19 1/4
23 5/8
19 1/4
Furnace
Sheet
Metal
Plenum
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