Heating and Ventilating

 

Heat transfer fluids - the little things count

Andrew Murray examines the importance of heating, ventilation and air conditioning (HVAC) systems in the school environment and the benefits of carefully selecting heat transfer fluids to ensure the lifespan and reliability of systems
It Is important for schools to have a reliable and well maintained HVAC system to ensure a healthy working environment for both pupils and teachers. While classroom temperatures need to be at a comfortable level, there should also be adequate ventilation to limit the concentration of carbon dioxide in all teaching and learning spaces.

The reliability of HVAC systems in schools is paramount as broken heating or cooling systems in the height of winter or summer can lead to pupil discomfort and even illness. This can be extremely damaging to a school's reputation, sometimes creating the need for schools to close while systems are repaired. So, what are the main challenges associated with heating or cooling systems and what is the impact of heat transfer fluids on system longevity and reliability?

The little things count
The importance of the quality and composition of heat transfer fluids should not be underestimated when specifying a fluid for an HVAC system. This is because the reliability and longevity of a system can depend on the heat transfer fluid used.

Many heat transfer fluids are glycol-based. While they are not particularly corrosive in concentrate form, corrosion challenges arise when they are diluted with water to achieve the required frost protection.

Another important consideration is the quality of the water used as the corrosive effect of water can vary considerably depending on its chemical composition. Hard or inferior water can cause bacterial growth and scaling within the system, as chemicals such as calcium and magnesium are introduced. This has the potential to reduce the system's lifespan and increase the need for maintenance and repairs.

As a result, mixing an inhibited glycol-based heat transfer fluid, with water of a sufficient quality, enables the system to last longer by reducing corrosion, bacteria and scaling. This results in cleaner circuits, efficient heat transfer and long-term cost benefits. The need for system repairs and to replace expensive equipment is reduced, saving both time and money for the installer and school.

But how can the installer really know the quality of the heat transfer fluid in operation? As the industry recognises the importance of corrosion prevention, an international standard, known as the ASTM D 1384 corrosion test standard is playing an increasingly important role. During the test, metals such as aluminium, iron, steel, brass, solder and copper, which are commonly used in heat transfer systems, are immersed in a glycol/water mixture. After this procedure, they are analysed in laboratory conditions for signs of corrosion.

This is an effective way to demonstrate the ability of the fluid to protect sufficiently against corrosion. However, as the standard remains voluntary, there is still a need for a greater focus in the industry on the importance of corrosion prevention and the quality of heat transfer fluids.

System maintenance
While selecting a fluid with the ASTM corrosion test standard can help to reduce the need for maintenance and repairs, regular quality checks remain important in the school environment. They are needed not only to confirm that the HVAC system is performing correctly, but that it is in good condition, with no signs of degradation or indications that it will fail. During maintenance, the glycol content within the system should also be monitored to maintain sufficient frost protection.

In addition, the various conditions under which heat transfer fluids are transferred, stored, heated and applied can all have an impact on their performance. As a result, regular quality checks should be performed in order to ensure that fluids are in an adequate condition for use all year round.

The perfect combination
In summary, the right combination of regular maintenance and carefully selected heat transfer fluids, can help installers to ensure that their systems remain operational and in good condition throughout the year. This is particularly vital in the school environment where failing or unreliable systems can lead to school closures, pupil illness, disrupted education and complaints. While heat transfer fluids may seem a small part of a system, poor quality fluids can potentially be very expensive and damaging.

// The author is the senior manager at Kilfrost's speciality fluids division //
1 April 2014

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