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’. This is Part 4 of a 10-part article.
Thorough documentation and effective training are critical for the long-term success and maintainability of any HVAC system. Freepik
A major emphasis of effective commissioning lies in ensuring the site is genuinely ready before the commissioning team mobilises. Skipping this critical pre-check phase inevitably leads to wasted time, resources, and project delays. As a blanket rule, if any item on the readiness checklist is ‘No’, the site is not ready for commissioning.
Essential site readiness checks:
- Diffuser and grille installation: Are all diffusers and grilles fully installed in their correct locations?
- Power supply to terminals: For fan coil units or VAV (Variable Air Volume) diffusers, is consistent power supplied to all terminal units?
- Ducting completeness and integrity: Is all ducting installed as per design? Are there any visible damages or incomplete sections, particularly flexible ducts?
- Full system installation: Is the entire HVAC system, including all major components (AHUs, fans, coils, controls), installed as per the design drawings?
- Snag list completion: Are all critical snags that might impede commissioning (for instance, missing filters, unsealed filter boxes, damaged flexible drops) rectified? It’s common to find flexible ducts damaged by other trades, such as ceiling installers or electricians, after initial installation; these must be identified and fixed.
- Power to fans and AHUs: Is the correct three-phase power (for instance, 400V) supplied to all fans and AHUs? Often, electricians prioritise getting power to the main phases, but commissioning requires the full, correct power supply for functional testing.
Adhering to ASHRAE Guideline 1.1-2007, and similar industry standards, provides comprehensive checklists that can be tailored to specific projects. These readily available resources ensure a systematic approach to site readiness, paving the way for efficient and effective commissioning.
System design fundamentals and basic calculations
A fundamental understanding of system design parameters and basic calculations is crucial for any commissioning professional. This proactive approach allows for on-site validation and quick identification of potential issues.
- Unit conversion and consistency: One of the most common pitfalls in airflow commissioning is inconsistency in units. Different suppliers may provide fan flow rates in cubic meters per hour (m3/h), cubic meters per second (m3/s), or litres per second (L/s). It is imperative to always be aware of and convert all values to a consistent unit before proceeding with any calculations. For example, converting m3/h to L/s requires specific conversion factors, and failure to do so will lead to erroneous results.
