How to ensure you have the right sized expansion tank

Tue 3rd Feb 2015 - 9:43am Energy and Heating How to ensure you have the right sized expansion tank

Benjamin Clarke

For the vast majority of experienced heating engineers and plumbers, fitting a new heating system to a home is a fairly straightforward process and is a job they will handle on a fairly regular basis. However, recent research has shown that detailed knowledge surrounding how to correctly size an expansion vessel is not quite so detailed within the industry.

In short, an expansion tank is a fairly small vessel that is used to protect closed central heating systems and hot water systems from excess water pressure caused by thermal expansion. Calculating the correct size of the vessel needed for a heating system is a fairly complex task that can cause a headache for the installer. If calculated incorrectly, it can also become a pain for the homeowner too, so getting it right is absolutely vital to the smooth and efficient running of a central heating system.

Fortunately, recent advancements in technology have seen the creation of an ‘expansion vessel sizing calculator’ that has made the task of calculating the right-sized expansion vessel much more simple. By using the calculator, you can input the boiler kW or the btu/hr output and then select the radiator and boiler type. The calculator will generate the system volume and you will need to the system volume in litres, read it against the system’s static height and the correct expansion vessel size will be calculated. The invention of this simple tool will hopefully do wonders for the quality of service that plumbers and heating engineers can provide, making things less stressful for them and creating happier customers in the process.

In addition to the ease of which the size calculations can be made, expansion vessels themselves have improved vastly, making them much more efficient than in years gone by.

One of the newer products is the nitrogen-filled vessel. Research over a 6 month period has shown that the nitrogen vessels did not lose any of their pre-set pressure. This is a great leap forward in terms of reliability and should benefit the heating industry as a whole because customers will have less need to contact a heating engineer regarding problems with underperforming expansion vessels.

When a heating installer is choosing an expansion vessel, the vessel must be accredited, independently tested and have had their manufacturing and security credentials validated. All expansion vessels, whether its the newer nitrogen-filled tanks or the older air-filled ones, must be approved under the Water Regulations Advisory Scheme (WRAS). They must also meet the standards under PED 97/23/EC Directive and BS EN1383:2007 closed expansion vessels with internal diaphragm for installation in water. Any installer not following these guidelines is not legally compliant and will be breaking the law, highlight the utmost importance of only using full authentic and accredited expansion vessels.

Article by Benjamin Clarke

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