23
6 DUCTWORK
Field ductwork must comply with the National Fire
Protection Association NFPA 90A, NFPA 90B and any
applicable local ordinance.
DANGER
Do not under any circumstances, connect return
ductwork to any other heat producing device
such as fireplace insert, stove, etc.
Unauthorized use of such devices may result in
fire, carbon monoxide poisoning, explosion,
personal injury or property damage.
Sheet metal ductwork in unconditioned spaces must be
insulated and covered with a vapor barrier. Fibrous
ductwork may be used if constructed and installed in
accordance with SMACNA Construction Standard on
Fibrous Glass Ducts. Ductwork must comply with
National Fire Protection Association as tested by UL
Standard 181 for Class I Air Ducts. Check local codes
for requirements on ductwork and insulation.
Duct system must be designed within the range of
external static pressure the unit is designed to
operate against. It is important that the system
airflow be adequate. Make sure supply and return
ductwork, grills, special filters, accessories, etc. are
accounted for in total resistance.
Design the duct system in accordance with “ACCA”
Manual “D” Design for Residential Winter and
Summer Air Conditioning and Equipment Selection.
Latest editions are available from: “ACCA” Air
Conditioning Contractors of America, 1513 16th
Street, N.W., Washington, D.C. 20036. If duct
system incorporates flexible air duct, be sure
pressure drop information (straight length plus all
turns) shown in “ACCA” Manual “D” is accounted for
in the system.
Supply plenum is attached to the 3/4” duct flanges
supplied with the unit. Attach flanges around the
blower outlet.
IMPORTANT: If an elbow is included in the plenum
close to the unit, it can not be smaller than the
dimensions of the supply duct flange on the unit.
IMPORTANT: The front flange on the return duct, if
connected to the blower casing, must not be
screwed into the area where the power wiring is
located. Drills or sharp screw points can damage
insulation on wires located inside unit.
Secure the supply and return ductwork to the unit
flanges, using proper fasteners for the type of duct
used and tape the duct-to-unit joint as required to
prevent air leaks.
WARNING
If appliances connected via an air duct system to
one or more rooms are installed in a room with an
area less than shown in section 3.5 Table 3-3,
that room shall be without continuously operating
open flames (e.g. an operating gas appliance) or
other potential ignition sources (for e.g. an
operating electric heater, hot surfaces). A
flame-producing device may be installed in the
same space if the device is provided with an
effective flame arrest.
For appliances connected via an air duct system
to one or more rooms, auxiliary devices which
may be a potential ignition source shall not be
installed in the duct work. Examples of such
potential ignition sources are hot surfaces with a
temperature exceeding 700°C and electric
switching devices.
For appliances connected via an air duct system
to one or more rooms, only auxiliary devices
approved by the appliance manufacturer or
declared suitable with the refrigerant shall be
installed in connecting ductwork.
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