RACA Journal September 2025 RACA_September2025 | Page 9

TECH TALK

THE ROLE OF AIRFLOW COMMISSIONING IN HVAC SYSTEMS

By Eamonn Ryan

The following is derived from a Cape Town TechTalk on 10 June by Theo van der Linde, Pr. Tech, head of project at SFI Group, on the topic‘ Basics of Airflow Commissioning’.

Airflow commissioning is a critical, comprehensive process ensuring HVAC systems perform precisely to design specifications, optimising energy efficiency, occupant comfort and indoor air quality. Neglecting thorough commissioning, particularly in early project stages, leads to costly remedial actions; rectifying issues at 98 % project completion is significantly more expensive than during initial construction.

Industry data from the US underscores this imperative: new buildings achieve approximately 60 % HVAC efficiency, while existing structures often operate at a mere 35 %. This disparity highlights proper airflow commissioning ' s vital role in energy consumption and overall building performance, especially for older buildings facing inherent structural limitations.

PRE-COMMISSIONING ESSENTIALS Successful commissioning hinges on meticulous precommissioning checks conducted early in the construction phase. This proactive approach is crucial for preventing minor issues from escalating into major, costly problems later.

Before any functional testing begins, thoroughly inspect and verify the installation of all HVAC equipment. This includes physically confirming that equipment is correctly positioned and secured, cross-referencing specifications against project designs, and ensuring the integrity of all components like coils, filters, fans and ductwork. Any unusual noises should also be assessed, as they might signal installation flaws or damaged parts.

Following installation verification, a‘ clean start’ check is essential before energising any equipment. This involves meticulously removing all construction debris, dust and foreign objects from ductwork, coils and equipment interiors to prevent airflow impediments or component damage. Confirming complete and secure power, control wiring and piping

connections is also vital. A formal sign-off, typically via a checklist, is then required from the commissioning team or responsible party to confirm the site ' s readiness, preventing wasted time and resources on premature testing.

The SAIRAC Cape Town TechTalk gets under way.

VERIFYING OPERATIONAL PERFORMANCE Once pre-checks are complete, functional commissioning verifies that the HVAC equipment operates as intended across various conditions.

This phase involves comprehensive testing of performance under diverse operational modes, including cooling, heating and ventilation. For instance, when commissioning a fan coil unit, actual airflow at diffusers and grilles is precisely measured using tools like a capture hood( balometer). Inlet and outlet air temperatures are verified to confirm the unit delivers specified cooling or heating capacity, with performance rigorously compared against Original Equipment Manufacturer( OEM) data and design expectations.

Crucially, control sequence testing ensures the entire control system operates correctly. This encompasses calibrating all sensors( temperature, pressure, humidity) and switches for accurate data relay. Safety controls and shutdown procedures, such as fire relays, are also tested to confirm appropriate responses, for example, shutting down an air handling unit or fan during an emergency condition. Identifying and rectifying any control issues early prevents expensive delays and potential safety hazards.

Finally, air balancing serves as a core component, ensuring proper air distribution throughout the building. This involves precisely adjusting dampers in ductwork and valves in hydraulic systems( acknowledging hydraulics, while outside the direct scope of airflow, are intrinsically linked to overall system performance) to achieve specified airflow rates. Technicians

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