Top system performance needs a holistic approach
A new British Standard and BSRIA recommendations on water quality management emphasise the value of a long-term strategy to water treatment, says Martin Wilkinson
It's all too common for water treatment to be seen as a 'nice to have' rather than an imperative when it comes to commercial heating systems. However, the recent introduction of British Standard BS8552, when taken alongside BSRIA's BG29/2012, provides a clear framework and guidance for the management of closed system water quality during construction projects.
Addressing the particular issues that often arise within commercial heating and water systems and stressing the importance of a complete approach to water treatment - from bottom to top level system management - the new recommendations help to ensure that a range of issues from corrosion damage, to system failure or even bacteriological contamination are avoided.
BS8552 also offers recommendations for water sampling and monitoring throughout a building's lifecycle. It remains an issue, though, that no firm guidelines for water quality in use exist, so the industry must still turn to water treatment specialists for advice, ideally one single point of contact that can offer informed advice, from pre-commissioning stage right through to the end of a building's life.
BSRIA, in association with a host of experts including Water Management Society, the British Association of Chemical Supplies, Institute of Corrosion and the Commissioning Specialist Association, is set to publish a new guide to water treatment this year, which will outline the processes and principals involved. This publication will only go to enhance the progress made by the new British Standards, as a rigorous and preventative maintenance regime will often negate the need for extensive replacement fees and avoid potential system failure.
Unless water quality is effectively managed in new systems and the latest sampling and monitoring codes of practice are followed, there is the potential for heat exchangers to become the 'weak link' in the system and compromise the integrity of the entire systems.
With modern boiler heat exchangers often more sensitive to the presence of air and dirt, the latest guidelines demonstrate the growing awareness of the need to treat the entire system, with the quality of the circulating fluid being of utmost importance in achieving maximum output from the modern, high efficient and energy saving plants.
Hydronics refers to the use of water as the heat-transfer medium in heating and cooling systems and the importance of hydronic stability should not be underestimated. It is critical to combat issues such as dirt and excess air within commercial applications because these factors can greatly compromise system performance and the longevity of the entire unit.
Though there's a growing awareness of the link between water treatment and system performance, too many commercial projects still rely heavily on chemicals alone, treating the symptoms of poor hydronic stability, rather than getting to the source of the issue, which can be a costly mistake to make.
Wherever possible, hydronic stability must be achieved from the outset, providing a strong foundation for a healthy system, resulting in continued optimum performance.
Only when addressing all four elements of hydronic stability - pressurisation, deaeration, dirt separation and the use of chemicals - can the system operate to maximum performance.
Securing the correct pressurisation is of primary importance, often being overlooked as a part of the ongoing water treatment process, rather than the first step to system efficiency. By initially addressing this key factor, problems arising at the next stages of the water treatment regime can be avoided.
Removing air from refill water
When the pressurisation of the system has been addressed, installing a combined vacuum deaerator and pressurisation unit is the next step, allowing the removal of air from the refill water before it even enters the system.
With the cavitation of pumps adding to system resistance, the increase in the electrical energy required for the pumps to move fluid around the system, as well as the corrosion of components, addressing the presence of air can greatly improve system performance and energy efficiency. Ignoring this issue may lead to irrevocable damage to the pump impeller- something that cannot be addressed by chemicals alone.
Equally, the introduction of a high powered dirt separator speeds up the cleaning of the system at the commissioning stage, as well as providing long term protection to major plant and equipment. Unlike traditional strainers that require considerable effort to clean, the latest range of next generation dirt separators are more likely to receive their annual maintenance, only requiring a simple blow down of the unit.
It is also important to note that systems should always be flushed and cleaned prior to installing the new boilers. However dosing with chemicals alone isn't the solution, as problems recur - reiterating the need to get to the root of the problem.
Previously used too often as a solution to water system issues, chemicals should be used in conjunction with other aspects of water treatment, not as a way to mask the system characteristics that caused the corrosion to occur in the first place.
It is this integrated approach to water treatment - the importance of which is confirmed by the recent BS 8552 - that provides the best platform for maximum performance, component longevity and energy efficiency.
// The author is national sales manager of Spirotech's UK commercial division //
17 April 2013