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The Condenser - A Closer Look at Blade Seals

In this Condenser article, we look at blade seals and their function on adjustable blades. Learn how these components provide tight closures and minimize pressure drop.

Dampers and adjustable louvers close off openings and ductwork when air stops moving through. Tight closing blades are important to air performance. A leaky damper makes it difficult to draw air through connected ducts. A leaky adjustable louver can result in water penetration that will damage your HVAC equipment. Blade seals ensure a tight closure, which minimizes leakage.

A backdraft damper blade with a blade seal.

Without seals, air will flow freely through the free space between the closed blades. This leakage can lead to air performance issues. Blades seals are designed to fill these spaces and minimize air leakage. They do not make the assembly airtight. Seals reduce the leakage to a negligible amount. Read our article on air leakage to understand how it can affect your system's performance.

Close-up image of a damper blade seal.

Most adjustable blades will have blade seals as a standard feature. These seals will be located along both edges of each blade. Seals can be installed over the edge of the blade or inside a groove along the blade’s edge. In both cases, the seals will overlap and cover the space between the closed blades. For airfoil blades, this groove will be offset from the blade’s edge since airfoil blades will overlap when closed. 

Airfoil blade seals overlapping.

Blade seals will press together every time the unit closes. That is why they are typically made from polyurethane, extruded silicone rubber, neoprene, or vinyl. These materials can be compressed many times over because they are flexible and durable. Technicians will need to replace blade seals when they are damaged. Check seals for signs of wear during your regular maintenance routine. Review our guide on damper maintenance for more pointers.

Blade seals close the gaps between blades. When they come together, these seals provide a tighter closure and minimize air leakage. Less air leakage means better air performance across your HVAC system.

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MCDLG is a collective of top-tier HVAC brands.
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