Supplied by Spoormaker & Partners www . refrigerationandaircon . co . za RACA Journal I February 2024 21
Feature filters , such as normal and HEPA ( high efficiency particulate air ) filters , which remove the smallest particles . By monitoring the pressure drops of fans , it is possible to determine when to do maintenance on or replace with clean filters .
Ziehl-Abegg ’ s fans are mounted in a fan wall that is part of the AHU manufacturer ’ s design . The fan wall box is designed to accommodate multiple fans , which are arranged in a fan wall which can have multiple fans in a unit , depending on the required flow rate . Pre-filters are installed before the fan to remove dust and other particles from the air . The fan sucks the air out and pressurises the system behind it , which usually contains cooling coils supplied by the OEMs .
“ Another way of doing it is to control the pressure downstream – after the filter , fans and coils – whereby it is possible to monitor and maintain the desired pressure setpoint , say 500 pascals , even if the filters get dirty . In that event , the system will increase the air flow to achieve the 500 pascals set point .”
Du Plessis describes the various best practices to consider when designing an AHU for HVAC systems . “ The design is critical to ensure that the HVAC system is operating at optimal efficiency . The cooling racks are designed to accommodate different types of fans , such as those that extract heat and vents that bring in cool air .”
Different data centres use different HVAC systems , such as air-cooled systems , liquid-cooled systems , and hybrid systems . The choice of HVAC system depends on the size and type of data centre , the amount of IT equipment , the ambient temperature and humidity , the desired temperature and humidity levels , and the budget .
“ Our fans are maintenance-free and have built-in diagnostics that measure the air temperature and motor temperature . Vibration sensors are also built into the fans to detect any issues . The EC fans work by receiving an AC supply sine wave , which is then rectified into a DC voltage . The brushless DC motor is highly efficient and quiet . It operates at the top efficiency level , IE5 .”
Noise is a significant issue in data centres . “ To address this , we use biomimicry to design our fans . We look at nature and design fan blades / impellers that make as little noise as possible while providing the exact airflow required . Our fans are so quiet that you can barely hear them , even when they are running at high speeds . Some blades are serrated ( imitating owls ’ wings ), which helps to break up larger vortices into smaller ones , reducing noise . This design of centrifugal plug fans on the other hand is inspired by the humpback whale ’ s tubercles on the leading edge of the flipper , which serves the same purpose of reducing noise and improving efficiency . These fans are used in AHUs for data centres . We apply the same design principles to our repellents , which are also designed to be quiet and efficient .” Energy efficiency is a particular factor in South Africa , especially given power outages are common . Many people are turning to solar power to address this issue . Du Plessis adds : “ Our fans
Jonker Bester , director at Spoormaker & Partners .
are designed to ramp up power slowly , which is important for systems that use solar or wind power . If you put full power into a normal AC motor at startup , it can cause a sudden spike in power , which can damage inverters and other components . With EC motors , the power ramps up slowly , allowing the solar or wind system to generate the extra power required . It takes up to 20 seconds ( configurable ) for the base motors to get up to speed , which is important to consider when designing a system .”
A BMS controls the temperature and humidity and requests more cooling from the AHUs . “ Best practices and infrastructure maintenance are essential to ensure that the AHUs meet our minimum best practices for installation . The plug fans that go into the units need to be sized correctly to ensure optimal performance . We work with consultants to determine the appropriate size and number of fans and build in redundancy as required for each unit . If the consultants don ’ t provide this information , we recommend the minimum size required to ensure optimal performance . Reducing the size of the fans can reduce efficiency and increase noise levels .”
The BMS system means , via a Modbus or other digital protocols , one can look at all the information on a phone or use a cloud system . From the moment a fan starts one can monitor the hours that it runs as well as the parameters . “ You can track the trend as the fan gets older : increasing vibration and temperatures ; thereby determining its lifespan and do preventative maintenance before anything breaks down . The bearings ’ lifespan is critical – in a worst-case scenario it should be about five years . But we have had fans that have been in use for 15 – 20 years , depending on their environment ,” he says . RACA
Supplied by Spoormaker & Partners www . refrigerationandaircon . co . za RACA Journal I February 2024 21