How do we calculate?
According to EN 12828: nominal volume Vn = (Ve + Vwr) × (pe + 1) ÷ (pe − p0). Ve is the expansion volume, Vwr the water reserve (0.5% of the volume, min. 3 L), p0 the pre-charge pressure (static height/10 + 0.2 bar), pe the final pressure (safety valve − 0.5 bar). If the water volume is unknown, 13 L per kW is used for radiators, 20 L for underfloor heating and 9 L for fan coils.
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