gf consulting   for healthy heating

Expansion Calculator

The calculations required to obtain the theoretical expansion of a complete heating system and it's total volume can be rather time consuming so this software is designed to simplify and speed up the process. This program is designed for small and medium sized heating systems operating at temperatures up to 105°C where the expansion can be sensibly accommodated by using one or two bladder vessels. This is only the case in sealed systems but the calculation is still applicable for determining the size of the feed and expansion tank in open vented systems. The total volume calculation is useful for determining the most suitable type of chemical treatment system and the potential operating costs. By selecting the water temperatures in the various sections of the heating system and using the default volumes (or known values) the total volume and expansion can be quickly estimated.
The program is particularly aimed at assisting heating engineers and designers who are working on potential biomass boiler installations where large accumulator vessels are a common occurrence. When installing log boilers we would usually recommend an accumulator vessel of at least 2,000 litre. A rough guide is 100 litre for every kW output but more can make summer operation easier.
The default values given are better than nothing but should be replaced with actual values where possible.

The method of calculation assumes that the system is filled at 20°C. It also assumes that the boiler, boiler room pipework, and accumulator will all be heated to the boiler operating temperature, the distribution pipework is heated to the mean temperature, and any radiator and underfloor heating circuits are heated to 5°C less than the flow temperature. The high pressure switch setting in the calculation is taken as 0.35bar less than the maximum working pressure, the start pressure setting equal to the cold fill pressure, and the low pressure switch setting the same as the gas charge pressure.

This program is offered free of charge in the hope that it will help heating engineers, consultants, architects, and designers to design and accommodate biomass boilers. We do not offer any warranty with the use of this software but trust that some will find it useful. If you have any comments, criticisms, or suggestions then please use the e-mail contact below.

Thank you for your interest,
George Fletcher

updated 18/04/2009