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Balancing energy and water conservation in HVAC


Steve Dawson, product manager – closed systems, from Guardian Water Treatment, looks at the most water and energy intensive processes in HVAC and how to improve their sustainability


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nergy and water are crucial to almost all HVAC systems, and preserving these resources, which, if wasted, impact sustainability goals, should be a priority for all building owners and maintenance teams. Poorly maintained water systems can negatively impact energy usage, by causing pipe corrosion and system fouling for example, and the very processes that keep these components clean can lead to large volumes of water wastage. Getting the balance right is a challenge, particularly where UK cooling demand is so high, at 10% of the total electricity usage, and only set the rise – more than tripling by 2050 according to estimates. Commercial buildings are the biggest electricity using culprits, including manufacturing facilities, offices and critical healthcare facilities. The state of the water inside closed HVAC


systems in particular can be hard to gauge. It is estimated that around 50% of commercial buildings have hidden problems with their HVAC systems that could be contributing to increased energy demand – anything up to 40% of total usage.


Buildings waste water from the outset


The construction, handover and ongoing maintenance of large commercial spaces wastes water. Pre-commissioning cleaning, for example, an essential element of new water system hand over, accounts for half of all water usage when a building is built. Cutting corners during this process, however, is a false economy - if not carried out effectively, repairs and breakdown will cost more in the long-run Water wastage occurs when large volumes of


water are used to flush the system, removing debris and maximising flow rates. Following flushing, biocide washing and chemical cleaning is used to remove bio-films and surface deposits, creating a stable surface more likely to withstand corrosion, backed-up by a corrosion inhibitor to further prevent damage. Finally, there’s back flushing, with yet more water used to remove any last remnants of debris. When it comes to the design of a water system,


correct construction is essential. Systems must be pressurised properly throughout the 24/7 cycle and expansion capacity needs to be specified correctly, alongside system pressures. Once the right foundations have been laid, these parameters must be maintained over the system’s lifetime.


Above: Steve Dawson, product manager – closed systems, from Guardian Water Treatment


How can water wastage be reduced?


There are ways to reduce the volumes of water used in precommission cleaning – advanced filtration, for example, can dramatically reduce the amount of water required while still ensuring that debris is sufficiently removed. This approach also cuts cleaning times, saving water and reducing time on the job when compared with traditional methods. Monitoring is also key during this process, with a


real-time indication of system condition, including the parameters that can be indicative of future corrosion issues. Microbiological activity must also


be checked for, allowing for prompt and pre-emptive treatment adjustments.


Beyond pre-commissioning cleaning


There are a number of parameters that real-time monitoring can detect, allowing action to be pre- emptive and more likely to stop major issues in their tracks. Managing pressure, for example, an important task throughout a water systems life, identifies oxygen ingress. If system pressures exceed the baseline, water losses may occur, requiring fresh, aerated water to top up the system. If pressures get too low, air could be sucked into the system. Dissolved oxygen is a contributing factor in almost all types of corrosion.


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