Krueger-HVAC Reminds Design Engineers to Specify Adjustment of Linear Slot Diffusers

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Krueger-HVAC, a leading manufacturer of air distribution products, reminds design engineers to specify the adjustment of linear slot diffusers before they are balanced.

Krueger Designflo (DFL)

Krueger Designflo (DFL)

These (rules) result in a good compromise between heating and cooling performance and have a chance of complying with the requirement in ASHRAE 62.1, which states that air thrown at 150 fpm must travel to within 4.5 feet from the floor.

If you have ever wondered why the perimeter of a room is uncomfortable and drafty, it could be the result of an unbalanced linear slot diffuser. These devices, typically identified by long, thin openings in the ceiling or around long curves, are often specified for their ability to blend with the building’s architecture and discretely deliver conditioned air to a given space. While manufacturers offer some models with fixed deflections, the majority of them are adjustable from horizontal to vertical and those with deflectors can often be moved to deflect right, left, or down.

Given variances of factory settings, installer manipulation, and general handling, these devices, once installed, are seldom positioned properly to distribute air in the space. As a rule of thumb, slot diffusers should be set to distribute air horizontally against the ceiling to produce optimal room air mixing. If located along a perimeter, they should be adjusted to discharge some air towards a window or wall and the rest horizontally, along the ceiling, into the room.

“These (rules) result in a good compromise between heating and cooling performance and have a chance of complying with the requirement in ASHRAE 62.1, which states that air thrown at 150 fpm must travel to within 4.5 feet from the floor,” says Dan Int-Hout, Chief Engineer of Krueger-HVAC. "Failure to comply with this requirement will demand a twenty-five percent increase in ventilation air to compensate for the inevitable short circuiting that will result. There is also a requirement that the discharge air must not be more than 15°F above room temperature, or the same penalty applies.”

To ensure that industry standards are met and that air is distributed properly, Krueger-HVAC recommends that engineers state clearly in their design documents that the diffuser’s slot(s) be adjusted, per instructions, prior to balancing. Making changes to the product’s settings before the system is balanced is important, as when the devices are adjusted from vertical to horizontal; the pressure drop tends to increase significantly and must be accounted for in the system balance. Otherwise, if left unadjusted, the outcome may very well result in a downpour of cold, uncomfortable air on occupants, which is not only unacceptable from a design point, but is entirely preventable.

For more information about air distribution best practices and how to meet industry standards, find a wealth of information on the Krueger-HVAC website, including a wide variety of educational white papers, published articles, and case studies. Learn more about HVAC’s selection of 1900 and DFL linear slot diffusers and other air distribution solutions through their on-line Product Catalog or download the e-Book from their Facebook page (http://www.facebook.com/KruegerHVAC).

About Krueger-HVAC
Krueger-HVAC is a leading manufacturer of air distribution solutions for commercial and industrial applications, including grilles, registers, diffusers, terminal units, fan coils, underfloor products, critical room products, fan filter units, displacement ventilation, as well as chilled beams. Krueger-HVAC is a division of Air System Components, Inc. (ASC). ASC is a subsidiary of Air Distribution Technologies, Inc.

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Lilli Wilbar
Krueger
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