How to Install a Flexible Air Conditioning Duct
Flexible air conditioning ducts are used either to transfer air from a duct-line main or to connect a register to a plenum in smaller HVAC systems. A flex duct consists of an inner liner made of aluminum or line plastic. A layer of insulation that eliminates condensation surrounds the inner liner and around the layer of insulation is a protective vapor barrier. The vapor barrier keeps the insulation intact and protects the insulation from water intrusion. When installing flexible duct, ensure that each layer is installed correctly. Does this Spark an idea?
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Things You'll Need
- Tape measure
- Length of flexible duct
- Large scissors
- Wire cutters
- Plastic duct-fastening strap
- Strap installation tool
- Duct tape
Instructions
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1
Measure the distance between the points the flexible duct will connect to, using the tape measure. To the length you measure, add twice the flexible duct diameter to the measurement for each 90-degree bend you need to place in the length of flexible duct during installation. For example, add 16 inches for each 90-degree bend in an 8-inch flexible duct.
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2
Stretch the length of flexible ductwork out on the floor or a stable work surface and place the stretched-out tape measure next to the flexible duct. Make sure that the end of the tape measure is aligned with the end of the flexible duct's inner liner.
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3
Open the pair of large scissors and push the lower blade of the scissors into the flexible duct at the length you need to cut the flexible duct. Make sure that the lower blade of the scissors pierces all three layers of the flexible duct.
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4
Cut around the flexible duct with the scissors. When you finish cutting the flexible duct, use the wire cutters to cut the support wire embedded in the inner layer of the flexible duct.
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5
Roll the vapor barrier and insulation back from the ends of the inner liner of the flexible duct. Expose at least 3 inches of the inner liner at both ends of the flexible duct.
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6
Slide the exposed inner liner at each end of the flexible duct over the ends of the connecting points between the HVAC system and the air distribution (register).
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7
Place a plastic duct-fastening strap around each end of the flexible duct, making sure that the strap is over the connecting points of the HVAC system.
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8
Tighten each plastic duct-fastening strap at each end of the flexible duct with the strap installation tool and wrap duct tape around the tightened plastic duct-fastening straps.
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9
Unroll the insulation and vapor barrier to cover the attached inner liner of the flexible duct and repeat steps 7 and 8 to complete the installation.
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References
- Photo Credit Zedcor Wholly Owned/PhotoObjects.net/Getty Images
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Comments
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Susan Crook
Mar 03, 2010
One more thing, Energy Stars says that if we don't install flexduct correctly when making a turn, it will kink (like a garden hose), causing restricted airflow and overworked HVAC units. There's a new inexpensive product called SMART Flow Elbow that snaps on to form a 90 degree angle, saving energy and wear-and-tear on the HVAC units. Thought you'd like to know.
