Commercial heating


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Test the waters G


Andy Green, commercial technical director at Baxi Heating, outlines best practices for maintaining high water quality within commercial heating systems


ood water quality is vital to safety as well as the longevity and efficiency of commercial heating systems. If undesirable substances


circulate and clog equipment, catastrophic failure and subsequent replacement of equipment could lead to huge costs and delays for organisations


Water contamination such as scale, settled sludge or microbial substances, in a closed-circuit system can have profound effects on the efficiency and lifespan of equipment. Any commercial water system must have been properly flushed, cleaned and (re-) commissioned to avoid contamination. Reduced efficiency and corrosion from


contaminated water could result in catastrophic system failure, incurring a complete replacement. The Building Services Research and Information Association (BSRIA) have created a benchmark of best practices for treating water and cleaning systems before and after the commissioning. Following these ensures efficient function and long- term reliability of any heating system.


Design considerations From the initial design stage of commercial water


Design considerations


systems, considerations must be made to deliver optimal water quality. A system’s designer has a multitude of aspects to consider before the installation and commissioning begins.


• Material choice – Most closed-circuit systems use steel, copper alloys and aluminium because of their low corrosion rates. Considering the impact of pH levels, chlorides, inhibitors and even the metals’ effect on each other within the system ensures effectiveness once commissioned.


• Flow rate and circulation – Too low a water velocity increases possibility of under-deposit corrosion, biofouling and microbially influenced corrosion (MIC) whereas high water velocity raises likelihood of turbulent erosion. Also, improper water circulation furthers risk of stagnation leading to microbial contamination.


• Operating temperature – In low-temperature oC,water faces risk of microbial


systems under 60 contamination because conditions promote bacterial multiplication. Large amounts of microbial bacterial multiplication. Large amounts of microbial


contamination can cause deposits that clog and corrode the system, reducing efficiency and ultimately requiring replacement.


system doesn’t allow for any water oxygenation that could lead to corrosion. If the system is adequately sealed and pressurised at the design stage, the installation will successfully prevent oxygenation from occurring.


Once these aspects have been considered, the designer and the engineers must carry out effective commissioning and maintenance of the system. According to BSRIA guidelines, pre-commissioning cleaning and flushing on top of regular monitoring is as important as the design process itself.


Taking time to clean Before commissioning, demand for quick


establishment of the heating supply often leads to common oversight of improper cleaning and flushing. Surfaces can become oxidised or contaminated with dirt or debris and, if contaminants and bacteria are not flushed from the system before commissioning, contaminated water within the system could lead to causing catastrophic failure.


Water quality may also be compromised after commissioning, requiring remedial flushing and cleaning. Whether this is MIC in stagnant water or corrosion from oxygenated water, a well-planned process is essential to clean the system and restore water quality. Both corrosion and contamination can make systems inefficient which has huge financial impacts, therefore remedial cleaning is a worthwhile investment to avoid this.


Controlling water quality


From the pre-commissioning stage to long after operations begin, water quality can be controlled effectively. Water softeners can be used to limit calcium and scale deposits, which form within heating systems where water hardness levels are above 150ppm. The role of softeners is to affect inhibitors or pH levels, mitigating potential corrosion and system failure.


If left untreated various bacteria can cause MIC, which prevents inhibitors from functioning due


to large deposits of slime creating biofil lm In this case, regular


m. biocide treatment can be


utilised to restrict the growth of bacteria.


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A neutral pH is necessary for the longevity of metal components. For instance, if an aluminium heat exchanger is in contact with water that has a high pH from a nitrate-based inhibitor, pit corrosion of the heat exchanger surface can occur.


A water treatment specialist can provide guidance on, and even carry out the chemical balancing to eliminate risks to the system.


The importance of monitoring Knowing when to flush the system after commissioning


or when to introduce chemicals is only possible with close monitoring of circulating water. The purpose of monitoring the water treatment programme is not only to optimise water quality, but also to confirm the system is fully efficient.


Whether testing pH, levels of microbial matter, water hardness or inhibitor levels, engineers can use an onsite test kit or send samples to a laboratory for analysis. Operatives can then determine substances for balanced, or whether it needs to be cleaned and flushed completely. Regular monitoring and testing of water quality within a commercial closed-circuit system should avoid catastrophic failure.


Don’t run the risk


Following these best practices will make sure that water quality within closed-circuit system remains at its highest, reducing corrosion and system failure derived from contamination.


• System sealing – It is vital that the design of the


Treating water, regular monitoring and seeking help from a specialist are all low-cost approaches to avoid customer dissatisfaction, preserve reputation and reduce unnecessary expenditure for poor operational efficiencies, component replacements and delay costs from system failure disruption.


22


March 2020


www.heatingandventilating.net


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