Feature product complies . Very often too , one gets lost in standards documents because of many external references and therefore interpretations vary . Secondly , products are not compared equally because of misleading information as Murray has already stated – which is also a very sensitive issue to address in the first place . Apples are not compared with apples ,” says Francois Schoombie , technical manager – EC Specialist at ebm-papst South Africa .
Comparison of efficiencies goes back to the research and development of a product , where testing results are the most important , and where many variances can occur . Although standard testing mechanisms are deployed by manufacturers , extraction and reporting of the data is what is important . Specific conditions of testing include , tolerances , volumes and pressure being some of the elements to generate accurate data . Further , standards refer to noise , vibration , construction material and mounting means for testing . All of which can produce different results .
From a calculation point of view , if an engineer designs a system , they would calculate the total pressure drop . The OEM or supplier needs to be given this information that is based on external static pressure and downline pressure that the fan needs to be capable of overcoming , or , otherwise known as the resistance in the total system . Further , location plays an important role in the calculations because as you move away from sea level , air density is lowered , which must also be factored in . Most fan curve diagrams are based on sea-level conditions .
Rickard Air Diffusion typically include , rooftop air handling units and a major portion of local manufacturers have adopted this technology in their products too .
The biggest advantage gained for direct-drive fans was that the belts were eliminated . It was initially determined that approximately 15 % savings were gained by removing pulleys and belts from a system . In line with the drive of energy efficiency ,
An internal cutaway view of a variable air volume diffuser .
THE PROGRESSION OF FAN TECHNOLOGY ” When it comes to extraction , inline fans have seen the most progress with a big move towards silent or ‘ quieter ’ fans . Energy efficiency has also become important for all HVAC components and is probably the biggest area of improvement over the last 10 to 15 years . Unfortunately , South Africa is taking longer to adopt energy-efficient products than for example Europe that has structured directives according to Energy-related Product ( ERP ) regulations that must comply to certain efficiency parameters . Sound attenuation has also seen a lot of development ( silencers ), and as mentioned , the development and incorporation of variable speed drives that add control thus bettering efficiency are other points to note . For other applications , Electronically Commutated ( EC ) fans have shown the most development ,” says Anderson .
Conventionally , and many years back , fans operated by belt-driven means . As technology progressed , aerodynamic properties and principles have been improved , as well as fan control leading to the latest innovations . EC is a term now widely used in industry and has produced very good results in the HVAC market , particularly for comfort cooling applications . These
www . hvacronline . co . za RACA Journal I June 2021 15