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Fire pump pressure settings

Question asked by gatrabolsi on Oct 1, 2018
Latest reply on Oct 4, 2018 by christophergates

NFPA 20 says that jockey pump stop point should equal the pump churn pressure plus the minimum static supply pressure. In our case we consider static supply pressure is about zero since water is taken from water tanks (not city potable water network). So jockey pump stop point should equal the pump churn pressure only. Now the question is which pump churn pressure to consider: electric duty or diesel standby? As per performance curves selected electric and diesel pumps have different churn pressures, with difference around 25 psi. Diesel pump 297 psi, electric 275 psi. When all pumps are interconnected and system is pressurized what pressure should be considered as system pressure? Maximum churn pressure which is of diesel pump (297 psi)? Electric duty pump 275 psi)? Average of both? How are they balanced? Shall we select both pumps so that their churn pressures would be the same? Any sources to learn about it?

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