PRODUCT DESIGN
36
CIRCULATING AIR AND FILTERS
DUCTWORK - AIR FLOW
Duct systems and register sizes must be properly designed
for the C.F.M. and external static pressure rating of the
furnace. Ductwork should be designed in accordance with
the recommended methods of "Air Conditioning Contrac-
tors of America" manual D.
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 Venti-
lating Systems, Pamphlets No. 90A and 90B.
A return air filter is not supplied with the furnace. The in-
staller must supply a means of filtering all of the return air.
Filter(s) shall comply with UL900 or CAN/ULC-S111 Stan-
dards. Damage or repairs due to the installation of the fur-
nace without the filters are not covered under the warranty.
MODEL
MINIMUM RECOMMENDED
FILTER SIZE^
DM80VC0604B*
1 - 16 X 25 Side or Bottom
DM80VC0805C*
1 - 16 X 25 Side or Bottom¹
DM80VC1005C*
2 - 16 X 25 Side or 20 X 25 Bottom
DD80VC0603B*
2 - 10 X 20 or 1 - 16 X 25 Top Return
DD80VC0805C*
2 - 14 X 20 or 1 - 20 X 25 Top Return
DD80VC1005C*
2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Larger filters m ay be used,
filters m ay also be centrally located
Upflow furnaces with air delivery of less than 1800 CFM:
Use one side return or one bottom return ductwork connec-
tion.
Upflow furnaces with air delivery of 1800 CFM or higher:
Use two side returns or one side return and one 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
opening will cause reduced airflow. For bottom return con-
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
connections to the furnace may be made with flexible joints
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 up-
stream side of the cooling unit to avoid condensation in the
heating element. With a parallel flow arrangement, the damp-
ers 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 pre-
vent 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
55°F
and
100°F
.
Consider installing an air cleaner with deep-pleated media
filter at the time of furnace installation. A deep-pleated filter
with a MERV rating of 8 (minimum) will often provide better
filtration to protect equipment and the air distribution sys-
tem than a standard 1" filter and often has lower static pres-
sure loss than a 1" filter. Also a deep-pleated filter will typi-
cally require less frequent replacement intervals. Avoid us-
ing highly restrictive 1" filters which produce static pressure
loss greater than .25" W.C. In some installations the mini-
mum filter size required (consult filter sizing chart ) will not
lend itself to a filter installation on the side of the furnace.
The installation of a centrally installed air cleaner cabinet or
a return duct filter installation may offer more practicality.
Clean Comfort™ brand MERV 11 air cleaners have 5¼” media
filters and are available in the following configurations. Con-
sult your distributor for information on our complete line of
IAQ Clean Comfort™ products.
UPRIGHT FILTER INSTALLATIONS
Depending on the installation and/or customer preference,
differing filter arrangements can be applied. Filters can be
installed in the central return register and a side panel exter-
nal filter rack kit (upflow filter kit # EFR01). As an alternative
a media air filter or electronic air cleaner can be used as the
requested filter. Refer to the following minimum filter require-
ment charts for determination of the minimum filter area to
ensure proper unit performance. The following figures show
possible filter locations.
NOTE:
A ductwork access door must
be used in counterflow applications to allow filter removal.
COUNTERFLOW FILTER INSTALLATION
This furnace has provisions for the installation of return air
filters at the counterflow top return. The furnace will accom-
modate the following filter sizes depending on cabinet size:
