AHU Ducting & Terminal Connection Setup: AC Grille Installation

In the 2026 Malaysian HVAC landscape, the installation of AC Grilles and Diffusers is the final and most visible stage of an AHU terminal connection. While often viewed as aesthetic, the grille is a critical engineering component that dictates "Air Throw," "Spread," and "Acoustic Comfort." Under MS 1525:2024 and DOSH 2026 Indoor Air Quality (IAQ) guidelines, a poorly installed grille can lead to stagnant air pockets or excessive noise, violating occupant comfort standards.

At EKG (Malaysia) SDN BHD, we treat grille installation as a precision balancing act to ensure your space remains Sterile, Silent, and Statutory-Compliant.

1. Types of Terminal Grilles & Their Engineering Roles

The choice of grille depends on the ceiling height and the required air distribution pattern.

2. The Statutory Framework: IAQ & Acoustics

Under DOSH 2026 and MS 1525:2024, grille installation must satisfy two primary human-centric metrics:

• Air Velocity (The 0.25 m/s Rule): To avoid the "Draft Effect," terminal velocity at the occupant level must not exceed 0.15 to 0.25 m/s. Improperly angled blades can cause "Cold Dumping," which leads to occupant complaints and energy waste.

• Acoustic Limits (NC 30-35): In Grade-A offices, the grille must not generate "regenerated noise." If the VFD-driven AHU is pushing air too fast through a small grille, it creates a high-pitched hiss. EKG ensures grilles are sized for a maximum neck velocity of 2.5 to 3.5 m/s.

• GITA Compliance: Using high-induction swirl diffusers can improve mixing efficiency, allowing for higher supply air temperatures and reducing the total energy load—a key factor for 100% Green Investment Tax Allowance eligibility.

3. Installation Engineering: The Plenum Box Connection

A grille is only as good as the terminal connection behind it. In 2026, EKG (Malaysia) SDN BHD mandates the use of Cushion Head Plenums (CHP).

1. Velocity Reduction: The plenum box allows the high-velocity air from the flexible duct to expand and slow down before hitting the grille, ensuring a uniform throw.

2. Internal Lagging: For boardrooms and recording studios, plenum boxes are internally lined with 25mm fiberglass or closed-cell foam to absorb high-frequency fan noise traveling through the duct.

3. Flexible Duct Limits: Under SMACNA 2026 guidelines, flexible duct connections to grilles should not exceed 1.5 to 2.0 meters. Excessive "coiling" of flex duct significantly increases static pressure, forcing the VFD to work harder and increasing your Specific Fan Power (SFP).

4. The "Fire Mode" Statutory Protocol

While grilles themselves are passive, their installation must adhere to BOMBA (JBPM) 2026 fire compartmentation rules.

• Ceiling Fire Dampers: If a grille is installed in a fire-rated ceiling membrane (e.g., in a protected lobby), a Ceiling Radiation Damper (Butterfly Damper) must be installed behind the grille.

• Fusible Link Mechanism: Upon reaching a specific temperature (typically 74°C), the link melts and snaps the damper shut, preventing fire from entering the ceiling void.

• BOMBA Audit: JBPM officers will inspect the presence of these dampers during the Fire Certificate (FC) witness test, especially in emergency escape routes.

5. Why Partner with EKG (Malaysia) SDN BHD?

• Technical Integrity: Our installations are led by mechanical specialists who use Anemometers to balance airflow across every grille, ensuring no "Hot Spots" in your office.

• Acoustic Excellence: We specialize in "Neck Sizing" to ensure your VFD-optimized AHU remains silent at the terminal point.

• EECA Compliance Support: Proper air distribution ensures the building hits its Building Energy Intensity (BEI) targets by preventing over-cooling of unoccupied areas.

Is your AC grille causing drafts or distracting noise? Contact EKG (Malaysia) SDN BHD today for a specialized Terminal Airflow & Acoustic Audit.