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is far less predictable, and air may become trapped anywhere. This is likely to lead to corrosion and sludge formation. In a small commercial installation such as a school building with three or four floors, or a modest office block, the heat source is often located in a plant room or basement. Above it lies a “static height” before you reach the highest emitters. The height difference in the system can cause changes in temperature and pressure, making it hard to decide where to place the deaerator. Should it go near the heat source, where the temperature is highest, or at the top of the system, where gases naturally collect? Or maybe in both places? Adding underfloor loops makes the setup even more complicated.


Why consider a mini-degasser?


This is where mini vacuum degassers offer an excellent solution. Spirotech’s S250 model can process up to 74 litres each hour, with the low pressure created through a combination of a speed- controlled centrifugal pump and a patented venturi spray nozzle. The degassed fluid is then returned to the system. If the unit operates within its working temperature range - typically 15 °C to 70 °C - it can reliably maintain a clean, gas-free system. The degassing process works continuously until all


the remaining dissolved gases and microbubbles in the system fluid are removed.


Vacuum degassers – associated with large applications


Whilst some people think vacuum degassers are only employed with large commercial or high- rise systems, this is not the case. Working on the principle of Henry’s Law, they are designed to remove trapped gases anywhere in the system, no matter how the pipework is arranged or how tall the building is. They work by pulling a small amount of water into a special vacuum chamber, where the pressure is reduced. This drop in pressure makes any dissolved air and tiny bubbles come out of the water. The released gases collect at the top and are safely vented away, while the cleaned water is sent back into the system. Crucially, the positioning of a vacuum degasser is no longer a potential problem compared to a deaerator. It can be installed at a convenient point - often on the return leg - rather than needing to be precisely located at the boiler or at the system crown. The degassing process runs continuously (or intermittently under control) until the fluid is virtually gas-free and then maintains that state over time. Some air will inevitably re-enter the system – either following maintenance, water top-ups or minor leaks. That’s why modern mini vacuum degassers use a timed or “boost” mode to balance effective gas removal with energy efficiency. In practice you might program a short “boost” cycle for the early weeks of a heating season (for instance


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8 hours per day for several weeks), followed by a transition to eco-mode. This accommodates the fact that water has sat idle (and cool) over summer and may have absorbed additional gas. Ongoing maintenance is straightforward usually


requiring the fine filter being cleaned annually and replacement of the the air vent every two years. And, crucially, the system will remain free of corrosive gas, without bubbling noises, without sludge accumulation, and with enhanced pump, valve and heat-emitter longevity. Mini vacuum degassers are a good choice


for schools. The UK government’s long-running Schools Rebuilding Programme seeks to modernise hundreds of schools, with energy upgrading a core objective. A mini vacuum degasser, properly integrated into a refurbished heating plant, helps optimise the performance of low-temperature heating systems, reduce maintenance costs, and lengthen system life - delivering a measurable carbon benefit. For small offices or multi-occupancy residential buildings converted to shared heating/cooling systems, the same logic applies. One compact vacuum degasser, correctly sized and placed, can serve an entire zone, even if spread over several storeys or involving underfloor networks. A properly installed and operated mini vacuum degasser delivering optimised system water will improve the carbon footprint of the entire heating/ cooling system.


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