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Welcome to our help and calculations section. From here we hope to assist with the calculations for various applications within our industry. Should you require any assistance with any of the following, please get in touch with us



Expansion vessel sizes can be quickly calculated using our table below *. (Based on DHW systems at 60 DegC). Sizing is simple. Simply:


1. Look up your system content (or nearest capacity shown which is above)

2. Look at the cold feed pressure in the red bar

3. Look up your maximum working pressure in the blue bar, either with a 0.5 BarG pressure difference between hot and cold or a 1.0 BarG difference

4. This will give the expansion vessel size


E.G. a system content of 2350 litres with a 3 BarG cold feed pressure and 4 BarG maximum working pressure would require a vessel with 300 litres.


Please click here to download a PDF sheet of the table

Please click here to download our spreadsheet calculation program for expansion vessels *

* - Disclaimer: This calculation sheet and the data produced is based on calculations made by Arbe Integrated Engineering. Arbe Integrated Engineering do not accept any liability for any expansion vessel sizings made on this spreadsheet by any person who is not employed by Arbe Integrated Engineering. It should be used for guidance only



The kW requirement can be quickly calculated using the table below, which shows the range of our standard calorifiers. The kW rating shown is the required heat input to raise the cylinder temperature by the given temperature rise in 1 hour. The tabulated figures can be doubled for a 1/2 recovery or halved for a 2 hour recovery etc. You can also calculate an exact requirement for any capacity cylinder by using the formula below the table

To calculate the heat input required for a certain capacity with a required temperature size, you can use a simple calculation for this


Heat Factor (0.001163) x capacity (litres) x temperature rise required = kW requirement

                                   Hours recovery


Example 1 - a 1000 litre calorifier needs to be heated from 5 to 60 DegC in 45 minutes


Therefore: 0.001163 x 1000 x 55 = 85.3 kW



Example 2 - a 2200 litre calorifier needs to be heated from 10 to 62 DegC in 90 minutes


Therefore: 0.001163 x 2200 x 52 = 88.7 kW



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