Achieving High Efficiency in Low-Temperature Hydronic Systems: A Holistic Approach

Low-temperature hydronic heating systems, operating at water temperatures ranging from 32 to 60 degrees Celsius, or 82 to 140 degrees Fahrenheit (respectively), offer energy savings and cost efficiency compared to traditional central heating systems, baseboard residential systems, or LTHW/LPHW commercial systems. However, these systems can become breeding grounds for bacteria, leading to reduced efficiencies and potential damage. In this article, we will explore the risks associated with bacterial growth in low-temperature hydronic systems and provide a comprehensive guide on how to protect and prevent such issues. 

The Risks of Bacteria Build-up in Low-Temperature Hydronic Systems 


Bacteria thrive in temperatures between 4.5°C and 60°C, with rapid growth occurring between 20°C (68°F) and 45°C (113°F) making low-temperature hydronic systems an ideal environment for their growth. As bacteria accumulate, they form biofilms, slimy layers that adhere to system surfaces. These biofilms impede heat transfer and significantly reduce efficiencies. Even less than 1mm of biofilm in a heat exchanger can result in up to a 30% loss in heat transfer (source). 

Bacterial growth also leads to microbial influenced corrosion (MIC), primarily affecting copper, iron, nickel, aluminium, and steel components. This corrosion can cause pinholes and leaks in the system, leading to the formation of biofilm, if untreated, which further exacerbates the system’s inefficiencies, by reducing flow rates, insulating materials from heat exchange and causing blockages.  

Methods to Protect Against Bacterial Growth 


To safeguard low-temperature hydronic systems from bacterial build-up, it is essential to follow our holistic approach. This process involves restoring system efficiency, cleaning it effectively, protecting it with inhibitors or sacrificial anodes (non-chemical treatment), and treating with biocides accordingly, as well as monitoring it regularly. 

Step 1: Restore the System Efficiency 


The use of an X-POT side stream filtration unit in closed loop systems offers a wide range of benefits. Firstly, it significantly improves the overall water quality, leading to enhanced efficiency and performance of the HVAC system. By removing contaminants, the unit helps maintain the cleanliness of heat exchangers, minimising the risk of fouling. This leads to improved heat transfer, reduced energy consumption, and lower maintenance costs. 

Furthermore, the X-POT helps preserve the integrity of the entire closed loop system. By removing impurities that can cause corrosion, it extends the lifespan of pipes, valves, and other components, reducing the need for frequent replacements. This not only saves money but also reduces the environmental impact associated with the production and disposal of HVAC equipment (Lifecyle) – ensuring a better overall embodied carbon footprint.

X-POT Compact

Step 2: Clean the System Effectively


Cleaning the low-temperature hydronic system is an essential step in removing scale, debris, and biofilms that hinder heat transfer and reduce efficiencies. VEXO’s X-PO35 Non-Flush Cleanser combined with X-PO10 Commercial Inhibitor, effectively eliminates these contaminants from the system. 

Over time, scale, debris, and biofilms can adhere to system components, and/or remain suspended in flow, gradually corroding them. By using a non-flush cleaner like VEXO X-PO35, these contaminants can be dislodged, and captured by the X-POT, preventing further damage to the components. Additionally, VEXO offers X-PO80 Biocide, which effectively tackles algae and other biological contaminations, ensuring a clean and efficient system.

Magnets from X-POT Compact Unit after 1-hour of dosing VEXO X-PO10 Inhibitor
Same System, 12 days later
X-POT Compact 20 Micron Filter

Step 3: Protect the System 


Protecting the low-temperature hydronic system with inhibitors is essential for maintaining its efficiency and longevity. VEXO’s X-PO10 commercial inhibitor provides a protective coating on all system components, controlling the effects of corrosion and scale. 

Using the VEXO X-PO10 Test Kit, test for Sodium Molybdate. The target should be 100 ppm or greater (100-300 ppm MoO4 max). X-PO10 is dosed at 0.36% v/v of system water volume to achieve minimum 100ppm Molybdate (MoO4). Systems that are heavily fouled will require additional inhibitor checks and dosing, this is due to X-PO10 gently liberating fine settled deposits and dissolving of scale, which leads to a reduction in active inhibitor reserve. 

Step 4: Control and Monitor the System 


To ensure long-term protection and optimal system performance, regularly monitoring and maintenance is crucial. Regular water testing helps monitor water quality levels and identify any potential issues. If necessary, the X-PO10 can be topped up to maintain its effectiveness. 

Regular maintenance and upkeep of the X-POT are also essential to its continued effectiveness. The frequency of maintenance will depend on factors such as water quality, system usage, and the type of filters employed. However, a general guideline is to inspect and clean the filters at least once every three months. Our PD-MONITOR is a great product for monitoring the condition of filters with audible alarms and BMS compatibility. 


During plantroom equipment upgrades VEXO’s S-BMS (Smart Building Management System) is a competitive solution to legacy BMS systems. VEXO’s S-BMS can also add greater plant room control and in some cases, achieve heating energy savings of up to 36%. 

Protecting low-temperature hydronic systems from bacterial build-up is essential for maintaining their efficiency and longevity. By following our holistic four-step process involving restoring, cleaning, protecting, and monitoring the system, risks associated with bacterial growth can be mitigated effectively. This will ensure low-temperature hydronic systems operate at their peak performance, offering energy savings and cost efficiency for years to come. 

Find out how our energy saving solutions can help your low-temperature hydronic systems.

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