How do we calculate?
According to EN 12845, design flow = design density × area of operation. The main line loss is calculated with the Hazen-Williams formula (p = 6.05×10⁵ × Q¹·⁸⁵ ÷ (C¹·⁸⁵ × d⁴·⁸⁷), bar/m) plus a 20% allowance for local losses. The smallest size with a velocity not exceeding 6 m/s and a line loss not exceeding 0.5 bar is selected. Pump pressure = minimum sprinkler pressure + height + line loss + 0.5 bar margin.
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