Reznor MAPS II Unit Installation Manual - Manual (Page 18)

Form I-MAPS II, Page 18
6. Mechanical 6.1 Duct Connections
Requirements and
Suggestions for
Installing Ducts
Supply and optional return air duct connections are made at the curb and can
be made prior to the unit being set on the curb. See FIGURE 5 for downflow
roof curb or FIGURE 7 for horizontal flow curb.
To facilitate startup, on systems with a heat section or in cooling only systems
with Option DU1, the discharge temperature sensor is factory-installed tem-
porarily in the outlet. Depending on the controls, the sensor must either be
re-located to the supply ductwork or disconnected. Because of the split burner
system, ductwork configuration and location of the sensor are especially impor-
tant on units with a gas heat section. See Paragraph 8.1 on ductwork configu-
ration requirements and instructions about re-locating the sensor.
CAUTION: An external duct system static pressure not within the
limits shown on the rating plate, or improper motor pulley or belt
adjustment, may overload the motor. See Hazard Levels, page 2.
• Type of Ductwork - The type of duct installation to be used depends in
part on the type of construction of the roof (whether wood joist, steelbar
joist, steel truss, pre-cast concrete) and the ceiling (whether hung, flush,
etc.).
• Ductwork Material - Rectangular duct should be constructed of not lighter
than No. 26 U.S. gauge galvanized iron or No. 24 B & S gauge aluminum.
• Ductwork Structure - All duct sections 24 inches (610mm) or wider, and
over 48 inches (1219mm) in length, should be cross broken on top and bot-
tom and should have standing seams or angle-iron braces. Joints should
be S and drive strip, or locked.
• Through Masonry Walls - No supply air duct should come in contact with
masonry walls. Insulate around all air ducts through masonry walls with not
less than 1/2" (13mm) of insulation. 1" (25mm) is recommended.
• Through Uncooled/Unheated Space - Insulate all exposed supply air
ducts passing through an uncooled or unheated space with at least 1/2" (1"
is recommended) of insulation.
• Duct Supports - Suspend all ducts securely from buildings members. Do
not support ducts solely by the unit duct connections.
• Duct Sizing - Proper sizing of the supply air ductwork is necessary to
ensure a satisfactory installation. The recognized authority for such infor-
mation is the Air Conditioning Contractors Association, 2800 Shirlington
Road, Suite 300, Arlington, VA 22206 (www.acca.org). A manual covering
duct sizing in detail may be purchased directly from them.
• Duct Connections - To minimize sound and vibration transmission, use
flexible duct connections. Ducts must be attached and sealed to provide
airtight connections.
• Return Air Duct/Grill Size - Make certain that return air ducting or grill has
a free area equal to the return duct size connection.
5.4 Rigging and
Lifting (cont'd)
5. Mounting (cont'd) Test lift the unit to be sure that it is secure. Lift the unit slowly, following safe
lifting procedures.
Failure to lift by the manufacturer's instructions could cause damage to the
equipment and/or personal injury or death. The equipment manufacturer is not
responsible for unsafe rigging or lifting procedures.
DANGER: To prevent injury, death, or equipment damage
caused by inadequate or improper rigging, test lift the unit
before attempting to install it on the roof. See Hazard Inten-
sity Levels, page 2.