The Expansion Vessel Calculator will help you to conform with BS 5449:1990, Section 3 by ensuring the expansion vessel on a central heating system is sized correctly.

Combi boilers are normally fitted with a vessel of between 6 and 8 litres. This internal vessel may not be sufficient on larger heating systems. You can use this app to calculate the total water contents of the system and it will tell you the vessel size required.

You will no longer have to use any inaccurate methods that calculate the water content from the boiler size. Use the app to find the water content of each radiator in turn for the entire house. Then enter the estimated length of 15mm, 22mm, 28mm and 35mm pipes, add any additional water contents such as for the boiler (2-4 litres normally) and a towel rail and then press the 'Calculate' button.

The app will show you the total water contents for the entire system and the vessel size required. If this size exceeds the vessel fitted to the boiler, an additional vessel will be required. Simple!


Email or Export:
Once you have your results you can email them directly from within the app or export them to another app that supports text files, such as Dropbox, Google Drive or Evernote.


Guide:
The app also comes with a built-in guide containing 5 pages:
• How expansion vessels work
• What goes wrong
• Common symptoms
• Vessel pressure guidance
• Repressurising instructions