Pump GPM Formula single phase and 3 phase
Pump GPM Formula:
Pump GPM=(HP x 2,800 )/(Press diff in feet of head)
To figure out the above formula you must first figure out what the pump is using for Horsepower currently using one of the formulas below depending on the whether you have a Single or Three Phase motor.
Single Phase Motor HP = (E x I x %Eff x PF)/746
3 Phase Motor HP = (E x I x %Eff x PF x 1.73)/746
Example Pump GPM Problem:
Pump Discharge Pressure: 70 PSIG.
Pump Suction Pressure: 10 PSIG.
Single Phase Operating Voltage: 230 V.
Operating Amperage: 18 A.
Motor Name Plate Efficiency: .8 or 80%.
Motor Name Plate Power Factor: .90.
Figure out your current operating Horsepower first.
Step 1: Single Phase Motor HP = (230 Volts x 18 Amps x .8 %Efficiency x .9 for a Power Factor)/(746 Watts)
Step 2: Single Phase Motor HP = 2980.8/(746 Watts)
Step 3: Single Phase Motor HP = 3.995 Current Horsepower the pump is operating at.
Next figure out your Pressure differential in feet of head between the discharge and the suction of the pump.
Step 4: Pressure Differential in feet of head = (Psiga -Psigb) x 2.31Ft
Step 5: Pressure Differential in feet of head = (70PSIG-10 PSIG) x 2.31Ft
Step 6: Pressure Differential in feet of head = 60 PSIG x 2.31Ft
Step 7: Pressure Differential in feet of head =138.6' of head
Then use the GPM Formula:
Pump GPM=(HP x 2,800 )/(Press diff in feet of head)
Step 8: Pump GPM=(3.995 HP x 2,800 )/(138.6 feet of head)
Step 9: Pump GPM=11,186/(138.6 )
Step 10: Pump GPM = 80.7