Unitary products group GY8S*UH Installation Manual Download Page 6

Page: 6 / 28

166753-UIM-C-0706

Unitary Products Group

RESIDENTIAL AND NON HUD MODULAR HOME

RESIDENTIAL AND NON HUD MODULAR HOME
UPFLOW RETURN PLENUM CONNECTION

UPFLOW RETURN PLENUM CONNECTION

Return air may enter the furnace through the side(s) or bottom depend-
ing on the type of application. Return air may not be connected into the
rear panel of the unit. In order to achieve the airflow indicated, it is rec-
ommended those applications over 1800 CFM (57 m³/min) use return
air from two sides, one side and the bottom or bottom only. For single
return application, see data and notes on blower performance data
tables in this manual.

BOTTOM RETURN AND ATTIC INSTALLATIONS

Bottom return applications normally pull return air through a base plat-
form or return air plenum. Be sure the return platform structure or return
air plenum is suitable to support the weight of the furnace.
The furnace base is equipped with a rectangular panel that can be
removed by performing the following steps:

Lay the furnace on its back.

Remove the screws from the toe plate.

Remove the toe plate.

Pull the base plate out of the furnace base.

Reinstall the toe plate and secure with the screws that were
removed.

Attic installations must meet all minimum clearances to combustibles
and have floor support with required service accessibility.

IMPORTANT:

If an external mounted filter rack is being used see the

instructions provided with that accessory for proper hole cut size.

HORIZONTAL

HORIZONTAL MODELS

MODELS

Horizontal Installations With a Cooling Coil Cabinet

The  furnace  should  be  installed  with  coil  cabinet  part  number  specifi-
cally  intended  for  Horizontal  application.  If  a  matching  cooling  coil  is
used, it may be placed directly on the furnace outlet and sealed to pre-
vent  leakage.  Follow  the  coil  instructions  for  installing  the  supply  ple-
num.  For  details  of  the  coil  cabinet  dimensions  and  installation
requirements, refer to the installation instructions supplied with the coil
cabinet
Attach the supply plenum to the air conditioning coil cabinet outlet duct
flanges  through  the  use  of  S  cleat  material  when  a  metal  plenum  is
used. The use of an approved flexible duct connector is recommended
on all installations. The connection to the furnace, air conditioning coil
cabinet and the supply plenum should be sealed to prevent air leakage.
The  sheet  metal  should  be  crosshatched  to  eliminate  any  popping  of
the sheet metal when the indoor fan is energized.
The minimum plenum height is 12” (30.5 cm). If the plenum is shorter
than 12” (30.5 cm) the turbulent air flow may cause the limit controls not
to operate as designed, or the limit controls may not operate at all. Also
the plastic drain pan in the air conditioning coil can overheat and melt.
Refer  to  the  installation  instructions  supplied  with  the  air  conditioning
coil for additional information.

Horizontal Installations Without a Cooling Coil Cabinet

When  installing  this  appliance,  the  furnace  must  be  installed  so  as  to
create  a  closed  duct  system,  the  supply  duct  system  must  be  con-
nected to the furnace outlet and the supply duct system must terminate
outside  the  space  containing  the  furnace.  When  replacing  an  existing
furnace, if the existing plenum is not the same size as the new furnace
then the existing plenum must be removed and a new plenum installed
that is the proper size for the new furnace.
Attach the supply plenum to the furnace outlet duct flanges through the
use  of  S  cleat  material  when  a  metal  plenum  is  used.  The  use  of  an
approved  flexible  duct  connector  is  recommended  on  all  installations.
This  connection  should  be  sealed  to  prevent  air  leakage.  The  sheet
metal  should  be  crosshatched  to  eliminate  any  popping  of  the  sheet
metal  when  the  indoor  fan  is  energized.  On  all  installations  without  a
coil, a removable access panel is recommended in the outlet duct such
that smoke  or reflected light  would be observable inside  the  casing to
indicate the presence of leaks in the heat exchanger. This access cover
shall be attached in such a manner as to prevent leaks.

Residential and Non Hud Modular Home Horizontal Return
Plenum Connections

The return duct system must be connected to the furnace inlet and the
return duct system must terminate outside the space containing the fur-
nace. When replacing an existing furnace, if the existing plenum is not
the  same  size  as  the  new  furnace  then  the  existing  plenum  must  be
removed and a new plenum installed that is the proper size for the new
furnace.
Attach the return plenum to the furnace inlet duct flanges. This is typi-
cally through the use of S cleat material when a metal plenum is used.
The use of an approved flexible duct connector is recommended on all
installations.  The  connection  of  the  plenum  to  the  furnace  and  all  the
ducts connecting to the plenum must be sealed to prevent air leakage.
The  sheet  metal  should  be  crosshatched  to  eliminate  any  popping  of
the sheet metal when the indoor fan is energized.
The duct system is a very important part of the installation. If the duct
system  is  improperly  sized  the  furnace  will  not  operate  properly.  The
ducts attached to the furnace must be of sufficient size so that the fur-
nace operates at the specified external static pressure and within the air
temperature rise specified on the nameplate.
Attic  installations  must  meet  all  minimum  clearances  to  combustibles
and have floor support with required service accessibility.