Selecting Air Diffusers - Verasys - LIT-12012331 - General System Information - Verasys System - 5.0

Verasys System Changeover Bypass Zoning System Design Application Note

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Verasys System
Document type
Application Note
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Air motion directly contributes to occupant comfort. Selecting air diffusers for a COBP Zoning System requires more care than a constant volume system due to varying airflow into the zones. It is best practice to use slot diffusers due to their superior performance at low airflows. Zone airflow is a variable volume. Lower-cost round or rectangular diffusers may not provide a satisfactory airflow in a COBP Zoning System. These diffusers can dump cold air at low flows in the cooling mode, resulting in insufficient room air motion at low airflows in the heating mode. Although high air motion in the heating mode is usually unwanted, a slot diffuser with a high induction ratio reduces room air stratification when the heating comes from a ceiling diffuser. Select linear slot diffusers for the airflow and throw suited to the specific installation or zone.

Sound level and throw at design flow are additional factors to consider in diffuser selection. Generally, multiple diffusers result in lower sound levels in the space, but you can balance this with the additional hardware and installation costs. It is best practice to locate slot diffusers near the perimeter or the outside wall, and direct the airflow into the room. Consult your diffuser supplier for the correct diffuser sizing and location.