From NFPA 20, 2003 A14.2.7
Fire Pump Settings. The fire pump system, when started by pressure drop, should be arranged as follows:
(a) The jockey pump stop point should equal the pump churn pressure plus the minimum static supply pressure.
(b) The jockey pump start point should be at least 0.68 bar (10 psi) less than the jockey pump stop point.
(c) The fire pump start point should be 0.34 bar (5 psi) less than the jockey pump start point. Use 0.68 bar (10 psi) increments for each additional pump.
(d) Where minimum run times are provided, the pump will continue to operate after attaining these pressures. The final pressures should not exceed the pressure rating of the system.
(e) Where the operating differential of pressure switches does not permit these settings, the settings should be as close as equipment will permit. The settings should be established by pressures observed on test gauges.
(f) Examples of fire pump settings follow (for SI units, 1 psi = 0.0689 bar):
i. Pump: 1000 gpm, 100 psi pump with churn pressure of 115 psi
ii. Suction supply: 50 psi from city — minimum static; 60 psi from city — maximum static
iii. Jockey pump stop = 115 psi + 50 psi = 165 psi
iv. Jockey pump start = 165 psi - 10 psi = 155 psi
v. Fire pump stop = 115 psi + 50 psi = 165 psi
vi. Fire pump start = 155 psi - 5 psi = 150 psi
vii. Fire pump maximum churn = 115 psi + 60 psi = 175 psi
