GM9S80 Service Manual

SYSTEM OPERATION
24
original wire as supplied with the furnace must be replaced,
it must be replaced with wiring material having a tempera-
ture rating of at least 105° C. Any replacement wiring must
be copper conductor.


Duct systems and register sizes must be properly designed
-
nace. Ductwork should be designed in accordance with the


A duct system should be installed in accordance with Stan-
dards of the National Board of Fire Underwriters for the In-
stallation of Air Conditioning, Warm Air Heating and Ventilat-
ing Systems, Pamphlets No. 90A and 90B.


shall comply with UL900 or CAN/ULC-S111 Standards.
Upflow / Horizontal
Models
Minimum Recommended Filter Size^
*0403A* 1 - 16 X 25 Side or 1 - 14 X 24 Bottom Return
*0603A* 1 - 16 X 25 Side or 1 - 14 X 24 Bottom Return
*0604B* 1 - 16 X 25 Side or Bottom Return
*0803B* 1 - 16 X 25 Side or Bottom Return
*0804B* 1 - 16 X 25 Side or Bottom Return
*0805C*
1 - 16 X 25 Side or Bottom Return¹
*0805D* 2 - 16 X 25 Side or 1 - 20 X 25 Bottom Return
*1005C* 2 - 16 X 25 Side or 1 - 20 X 25 Bottom Return
*1205D* 2 - 16 X 25 Side or 1 - 24 X 24 Bottom Return
Downflow Models Minimum Recommended Filter Size^
*0403A* 2 - 10 X 20 or 1 - 14 X 25 Top Return
*0603A* 2 - 10 X 20 or 1 - 14 X 25 Top Return
*0804B* 2 - 14 X 20 or 1 - 16 X 25 Top Return
*1005C* 2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Other size filters of equal or greater dimensions may be used, filters may
also be centrally located
¹ = us e 2 - 16 X 25 fi l te rs and two s i de returns or 20 X 25 fi l te r on bottom
return if furnace is connected to a cooling unit over 4 tons nominal capacity
Upow furnaces with air delivery of less than 1800 CFM:
Use one side return or one bottom return ductwork connection.
Upow furnaces with air delivery of 1800 CFM or higher:
Use two side returns or bottom return connection.
Guide dimples locate the side and bottom return cutout lo-
cations. Use a straight edge to scribe lines connecting the
dimples. Cut out the opening on these lines. An undersized
-
nection, remove the bottom of the cabinet before setting the
furnace on the raised platform or return air duct.
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

to reduce noise transmission, if desired. If a central return is
used, a connecting duct must be installed between the unit
and the utility room wall so the blower will not interfere with
combustion air or draft. The 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


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 heating, the temperature of the return
air entering the furnace must be between  and .

Depending on the installation and/or customer preference,
󰀨  
-
-


       
area to ensure proper unit performance.

This furnace has provisions for the installation of return air


 Filters can also be installed elsewhere in the duct
system such as a central return.


horizontal installations. For most installations it is preferable


simple by merely removing the grille, rather than going into
the attic or crawl space.



     -

to mount over the indoor blower compartment area of either

for attaching return air ductwork.