If we install duty stand by fire pumps, what shall the differential pressure between them to insure there is no false starting.Best regards.
I would be appreciated if I got the correct answer as soon as possible.
I would suggest about 10psi lower than your primary pump starting psi.
Activation of starting psi on lead fire pump I believe should be 10-15 psi lower than you maintain your system operating psi. due to normal fluctuation of system loop psi. The lag or second fire pump should be set another 10 psi lower than you set the lead pump activation setting. At our site run our system loop ( Jockey) pump at 118 and our lead pump is set to activate at 95 psi and second pump will activate when psi drops below 85 psi.
EN 12845 states "The first pumpset shall start automatically when the pressure in the trunk main falls to a value of no less than 0,8p, where p is the pressure at the closed valve condition. Where two pumpsets are installed, thesecond pump shall start before the pressure falls to a value of no less than 0,6p. Once the pump has started,it shall continue to run until stopped manually.". So if your jockey pump keeps a pressure of 118 psi the lead pump would start before the pressure drop to 94,4 psi and the second pump will be activated when psi drops below 70,8 psi. So Michael Peirson's design would also fulfill European standards.
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