Service Manual

PRODUCT DESIGN
38
DISABLE OFF
ENABLE ON
SWITCH 2
Trim Enable
S5
•Profile D ramps up to 50% of the demand for 1/2 minute,
then ramps to 85% of the full cooling demand airflow
and operates there for approximately 7 1/2 minutes.
The motor then steps up to the full demand airflow.
Profile D has a 1/2 minute at 50% airflow OFF delay.
OFF
OFF
CIRCULATING AIR AND FILTERS
DUCTWORK - AIRFLOW
Duct systems and register sizes must be properly designed
for the C.F.M. and external static pressure rating of the fur-
nace. Ductwork should be designed in accordance with the
recommended methods of "Air Condition Contractors 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 the warranty will be voided.
MODEL
MINIMUM RECOMMENDED
FILTER SIZE^
*MVC80604B* 1 - 16 X 25 Side or Bottom
*MVC80805C* 1 - 16 X 25 Side or Bottom¹
*MVC81005C* 2 - 16 X 25 Side or 20 X 25 Bottom
ADVC80603BN* 2 - 10 X 20 or 1 - 16 X 25 Top Return
ADVC80805C* 2 - 14 X 20 or 1 - 20 X 25 Top Return
ADVC81005C* 2 - 14 X 20 or 1 - 20 X 25 Top Return
^ Larger filters may be used,
filters may also be centrally located
¹ = use 2 - 16 X 25 filters and two side returns or 20 X
25 filter on bottom return if furnace is connected to a
cooling unit over 4 tons nominal capacity
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 bottom return connection or a
combination of both.
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-