Compiled by Eamonn Ryan from the 3rd SAIRAC Johannesburg Tech Talk online presentation by Edward Erasmus on the topic ‘Guided Approach to Applying UV-C to Mechanical Ventilation Systems’
Edward Erasmus represents Sani UV-C, a company that specialises in UV-C application used across various applications including cold rooms, vehicle transportation, HVAC systems, and water systems.
A section of the audience at a typical inperson SAIRAC Tech Talk. © RACA Journal
UV-C light is a form of invisible light that effectively destroys the DNA of viruses and bacteria. This destruction occurs when pathogens are exposed to UV-C light for a sufficient duration, rendering them incapable of reproduction. The use of UV-C for disinfection has been well-documented and proven over hundreds of years.
Erasmus emphasised the importance of understanding the correct application of UV-C technology to ensure cost-effectiveness and efficacy. He pointed out common issues such as the tendency of users to purchase UV-C devices online without proper guidance on their application, leading to suboptimal results. He recommended selecting robust, quality UV-C fixtures and performing regular maintenance.
Erasmus also discussed the relationship between UV-C light and ozone. “Ozone is generated when UV-C light splits an oxygen molecule (O2) into single oxygen atoms (O1), which then bond with O2 molecules to form ozone (O3). This ozone is useful for surface sanitation, odour control, and in the treatment of drinking water.”
One of the key challenges Erasmus noted is the misconception about the placement and effectiveness of UV-C lamps. Users often mistakenly place UV-C devices in areas without considering factors such as air flow and exposure time. He stressed the importance of a guided approach, where the positioning and maintenance of UV-C fixtures are strategically planned to maximise their disinfection capabilities.
Durability and installation concerns
Erasmus highlighted the importance of installing durable fixtures, particularly in environments with high moisture, potential mould growth, and bio-loading areas. “Without robust fixtures, components may need to be replaced frequently, leading to increased costs and inefficiencies. Properly engineered UV-C fixtures are essential for ensuring longevity and consistent performance in HVAC systems and cold rooms.”
A common issue is the overuse of lamps in UV-C devices. Many suppliers offer fixtures with an excessive number of lamps, which can be both costly and inefficient. Other companies focus on maximising energy output while minimising the number of lamps required. This approach not only reduces initial costs but also makes the technology more accessible and economically viable for users.
“Budgeting for the long-term maintenance of UV-C systems is another critical aspect. UV-C lamps typically have a lifespan of around 9 000 hours, or roughly one year when operated continuously. Users often neglect to budget for replacement lamps and other maintenance needs, leading to lapses in system efficacy. It is vital to allocate funds for regular maintenance to ensure the continued effectiveness of the UV-C systems.
“Many users purchase UV-C devices from overseas suppliers, leading to difficulties in obtaining replacement parts. Local availability of components is crucial for the sustainability and reliability of UV-C systems. Purchasing UV-C products requires careful consideration beyond what is visible online. There are significant variations in lamp sizes and the specific requirements for different applications. Users must conduct thorough cost comparisons and ensure they choose the most effective and economical solutions for their HVAC or ventilation systems.”
Safety is paramount when dealing with UV-C light, which can be harmful to skin and eyes. Erasmus stressed the need for proper setup and maintenance of UV-C systems to prevent accidents. Fixtures are equipped with safety warnings and guidance documents to ensure proper handling, especially in areas frequented by children or animals. Technical support is also available to help users choose the right fixtures for their specific applications.
A wide range of UV-C fixtures designed for different environments, such as ambulances, mobile clinics, and TB hospitals. Mobile units are available for flexible use in various settings. The emphasis during Covid-19 on surface disinfection highlighted the importance of air quality.
“Effective air disinfection can lead to significant reductions in surface contamination. When approaching a facility, it is crucial to address air, surface, and water disinfection. For facilities involving food products or people, ensuring minimal risk is essential. By providing UV-C solutions for air, surface, and water disinfection, facilities can maintain high hygiene standards, safeguarding both products and clients.”
Types of UV-C applications in HVAC systems
Erasmus distinguished between mechanical and added ventilation UV applications: “Mechanical ventilation UV involves integrating UV-C into existing HVAC systems, typically behind evaporator cooling units, to sterilise circulating air. Added ventilation UV is used in areas with limited mechanical ventilation and high occupancy, requiring additional ventilation and sterilisation through units equipped with fans.”
A common mistake is placing UV-C lamps only in coil areas of HVAC systems. While this can help with moisture and mould control, a comprehensive approach involves addressing multiple areas:
Coil area: Moisture and mould build-up are common here. UV-C can prevent growth and maintain cleanliness
Filter bank area: Care must be taken to avoid UV exposure to certain filter materials like HEPA filters, which can degrade. More durable filters, like washable pre-filters, can withstand UV exposure
Air mixing chamber: Installing UV-C in large air mixing chambers can effectively sterilise incoming and return air
Ducting: UV-C can be installed in return air ducts and supply air ducts to prevent mould growth and maintain clean ducts. Placement at the beginning of the ducting ensures maximum effectiveness and minimal bio-load build-up
By strategically placing UV-C fixtures in these areas, HVAC systems can achieve thorough and Positive Pressure and UV Installation.
One effective approach to maintaining air quality is creating positive pressure zones, with extraction through bathrooms or exit points. “To implement this, you can install UV fixtures at accessible points in the ductwork, enhancing the system’s overall efficacy.”
Erasmus offered some further tips:
A crucial step in managing your HVAC system is proper labelling and mapping. Diagrams and summaries of different areas, such as mixing chambers (A to E), help in visualising and understanding the system’s layout. This practice is particularly useful when deciding where to install UV fixtures.
When it comes to fixtures, 99% of the time, intercooler units for ducting and fresh air ducts are used. These fixtures are typically not available locally and may need to be imported. The variability in duct sizes means that a standard fixture may not always suffice; sometimes, a single small lamp on one side of the duct won’t be effective.
For cooling coil areas, it’s vital to provide accurate dimensions and velocities to the supplier. This information helps in recommending the correct UV unit for installation, ensuring efficient coil cleaning and maintenance cost reduction. UV units can prevent mould buildup, commonly mistaken for dirt, improving overall hygiene.
To ensure proper UV coverage in coil areas, measure the area accurately and assess the air velocity. The UV fixture must be capable of handling the required volume, which is usually measured in cubic meters per second. Durable aluminium powder-coated fixtures are commonly used, equipped with reflectors and designed for different mounting needs.
Duct units are crucial for supply or return air ducting. It’s essential to choose the right unit based on duct shape and size. Extension arms ensure the lamp is positioned centrally within the duct, maximising effectiveness. Safety inspection windows allow for visual checks, confirming the unit’s operation.
Practical installation tips
Extension arms: These are necessary to position the UV lamp at the correct depth within the duct
Inspection windows: These provide a simple way to verify if the UV light is functioning without needing to open the duct
Power supply: Ensure a nearby power point with at least a 5-amp plug to power the UV unit.
Plenum chambers: In cases where direct access is difficult, plenums can be built over return vents to facilitate proper installation.
“By focusing on these aspects, mechanical engineers can effectively incorporate UV fixtures into HVAC systems, enhancing air quality and operational efficiency. This approach not only improves system performance but also reduces maintenance costs and extends the lifespan of the HVAC components,” says Erasmus.
The remainder of this long and insightful presentation can be found online.
