Tekmar519

Remember, the higher is the difference between ph,dov and ph,min, the smaller pressure fluctuations will appear in the system but the expansion vessel will have to be bigger.

The water volume in a heating system is 200 l, its max. working temperature is 80°C, max. pressure in the system is 2.5 bar, the system highest point is 7 m above the boiler room, min. boiler pressure is 0.5 bar.

Tekmar508

The calculation presumes a heating system layout as in the Fig., the boiler room with a boiler and expansion vessel at the lowest point of the heating system. For a different layout the calculation is done in the same manner, related to the position of the expansion vessel, and for other heating system components the hydrostatic pressure difference shall be taken into account. An expansion vessel for drinking water shall be designed in the same way, just substituting the min. pressure by water mains pressure or switch-off pressure of a whole house water pressure boosting pump; instead of the heating system volume the volume of a DHW heater and re-circulation piping shall be used. If the water mains pressure is too high and the calculated expansion vessel size is too big, a pressure reducing valve shall be used.