BSEE


ABB’s Carl Turbi explains how taking a whole life cycle approach with an installed base of variable speed drives (VSDs) reduces potenal failures by ensuring mely maintenance and a consistent programme for replacements and upgrades.


he HVAC system is often the largest consumer of energy in buildings, particularly within the retail, commercial, healthcare and leisure sectors. The motors that drive pumps and fans are major power users. Therefore, anything that reduces energy usage can potentially improve the efficiency of applications such as air handling units, booster sets, extraction fans, chilled and hot water pumps that comprise the HVAC system. With their ability to regulate motor speed to meet demand, variable speed drives (VSDs) are the preferred choice for improving the HVAC system’s energy efficiency. VSDs can be seamlessly integrated into existing systems and their operation can have a significant impact on a building's overall sustainability goals.


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Modern VSDs are extremely reliable and can provide many years of incident-free operation. Operating in good conditions - away from dusty environments, extreme temperatures and hazardous areas – a VSD can have a mean time between failure (MTBF) of over half a million hours or the equivalent of 62 years.


However, VSDs are not indestructible. If operated without the appropriate maintenance, they may not deliver the optimum savings throughout the application’s lifetime and run the risk of premature failure. If the VSD or its components are obsolete it may be very difficult to repair quickly, potentially leading to costly downtime. This can be particularly important if the HVAC systems are critical to the operation of a site, for instance maintaining cooling in a data centre.


It is estimated that up to 80 percent of VSDs in the UK are operated without any kind of systematic maintenance, making it more likely that when failures happen they will occur unexpectedly, causing unnecessary disruption. The best way to ensure that regular maintenance is carried out is by taking a whole life approach, which means taking a holistic view of all VSDs in a fleet both individually and collectively. Each VSD may be at a different stage in its life cycle, and therefore have different maintenance needs, while some may be nearing the end of their operational life and may be candidates for replacement or upgrade.


MAINTENANCE AND REFURBISHMENT


How a whole life cycle approach boosts a building's climate control


On board help


When it comes to maintenance, modern VSDs can provide lots of help. They have numerous HVAC specific parameter settings such as supply fan, return fan and cooling tower, which can dramatically reduce set-up time and ensure they offer the maximum efficiency and uptime by operating correctly. The VSD’s panel can help users start up the drive, maintain and diagnose faults, while there may also be an on-board fault history that shows when the fault occurred, speeding up drive repair.


The VSD can detect dirty filters, which can cause a pressure drop and increased current, meaning the fan will need to work harder, and use more energy to supply air volume demand.


A Life Cycle Assessment makes it easy to track the maintenance and life cycle needs of your VSD installed base


30 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MARCH 2021


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