www . refrigerationandaircon . co . za RACA Journal I March 2024 25
Feature all electrical terminals . This includes inspecting all fans and ensuring there are no bearing noises . Belt drive fans require attention to alignment and prevention of slipping and wear .
• Overall component check : Basic AHUs may include components like fans , coils , heaters and variable frequency drives . Regular checks should encompass a comprehensive evaluation of each component ' s functionality , examining connections , voltages and amperages to ensure balanced operation .
• Airflow measurement : Measuring airflow from the supply fan is essential to verify that it falls within design parameters . This check helps maintain the intended airflow , contributing to the overall efficiency of the AHU .
• External inspection : A visual inspection of both internal and external components and surfaces is crucial to identify any signs of damage or corrosion . This external assessment ensures the AHU ' s structural integrity and helps preemptively address potential issues .
Mlangeni describes some of the common problems associated with AHUs :
• Airflow obstructions : The main purpose of the filters is to remove dust and debris from the air and keep it out of system . If they get overloaded and clogged , this results in obstructions that limit the airflow causing the AHU to be less efficient .
• Condensation blockages : When filters are overloaded , dust and other particles in the air enter the coil and drip out with the water as air passes through the coils . They block the condensate drain over time and cause water to accumulate in the drain pan .
• Fan blade issues : Fan blades are likely to bend or become loose during operation because they are attached to a moving part . A damaged blade has a major impact on the air flow .
WHAT ARE THE BEST PRACTICES FOR SELECTING AN AHU ? Mlangeni explains that when selecting an air handling unit , the position and arrangement and type of components inside the AHU are important for reasons of cost , efficiency and for ensuring the trouble-free operation .
“ First , carefully assess the specific requirements of the building to be served by the AHU . Determine the required airflow rate , temperature , humidity and filtration level – then the AHU can be selected to meet them .
“ The type and efficiency of the AHU components will have a significant impact on overall performance . High efficiency fans , motors and heat recovery units can reduce energy consumption .
“ The AHU should be equipped with appropriate controls to allow for precise and efficient operation . This may include different sensors and controllers that monitor and maintain desired temperature , humidity and filtration levels . These controls optimise performance and energy efficiency .
“ The AHU should be designed for easy access and maintenance . This will help to ensure that the unit is operating at its peak performance and that any potential problems can be quickly identified and resolved ,” he adds .
A LOOK AT RECENT INNOVATIONS IN THE AHU INDUSTRY There has been a significant transformation in the design and functionality of AHUs , says Roelofse . “ One noteworthy area of innovation has been in the evolution of fans , particularly the adoption of electronically commutated fans ( EC fans ). Daikin and other leading manufacturers have been at the forefront of integrating these fans into AHU designs . They have proven to be a game-changer by addressing key challenges associated with traditional belt drive fans . They represent a more compact alternative to traditional belt drive fans . The elimination of pulleys and belts reduces the bulkiness of the fan and reduced maintenance , allowing for a more streamlined and spaceefficient AHU design , reflecting the demand for efficient use of space in commercial and office environments . This is particularly crucial in areas where architects prioritise maximising usable space without compromising on HVAC performance .”
Additionally , notes Roelofse , “ EC fans offer unprecedented flexibility and redundancy options . Rather than relying on a single large centrifugal fan , multiple EC fans of the same size can be employed . This not only enhances redundancy but also allows for more flexible and efficient unit configurations .
“ EC fans can be controlled seamlessly across the entire operating spectrum without the need for external variable frequency drives . Integration with building management systems ( BMS ) enables direct control , providing increased efficiency and eliminating the need for additional electrical components .
“ An additional benefit is their adaptability to external factors ,” says Roelofse . “ For instance , pressure sensors connected to filters can be utilised to monitor air quality . As filters accumulate dirt , the pressure drop increases . This
“ AHUS are highly customisable and have countless combinations of filters , coils , fans and other section combinations to meet application requirements .”
www . refrigerationandaircon . co . za RACA Journal I March 2024 25