A centrifugal pump pressure switch is an automatic control device used to start and stop the pump based on system pressure demands. It ensures that the pump operates only when needed, maintaining desired pressure levels in water supply systems, irrigation, industrial processes, and HVAC applications.
Function:
Monitors discharge pressure (or suction pressure in some cases).
Activates the pump when pressure drops below a set level (cut-in pressure).
Stops the pump when pressure reaches the upper limit (cut-out pressure).
Common Applications:
Domestic water supply (well pumps, booster pumps).
Industrial hydraulic systems.
Firefighting systems.
Irrigation systems.
| Type | Description |
|---|---|
| Mechanical | Uses a spring and diaphragm to detect pressure changes. Adjustable via screws. |
| Electronic/Digital | More precise, programmable, and often includes displays for monitoring. |
| Differential | Controls the range between cut-in and cut-out pressures. |
Cut-In Pressure (Start Pressure)
The minimum pressure at which the pump starts (e.g., 30 psi).
Cut-Out Pressure (Stop Pressure)
The maximum pressure at which the pump stops (e.g., 50 psi).
Differential (Pressure Range)
The difference between cut-in and cut-out (e.g., 20 psi in the example above).
Example:
Cut-In: 30 psi → Pump starts when pressure ≤ 30 psi.
Cut-Out: 50 psi → Pump stops when pressure ≥ 50 psi.
Differential: 20 psi (fixed or adjustable).
Typical Setup:
The switch is wired between the power supply and the pump motor.
Some switches include low-pressure cutoff (dry-run protection).
Installation Tips:
Mount near the pump discharge (avoid vibration interference).
Use a pressure gauge for calibration.
Ensure proper sealing to prevent leaks.
| Problem | Possible Cause | Solution |
|---|---|---|
| Pump won’t start | Low voltage, stuck contacts, wrong setting | Check power, clean contacts, adjust. |
| Pump short-cycling | Small differential, waterlogged tank | Increase differential, check tank. |
| Pump doesn’t reach cut-out | Weak pump, leaking system, incorrect setting | Inspect pump, fix leaks, recalibrate. |
Locate the adjustment nuts:
Larger nut → Cut-in & cut-out (changes both).
Smaller nut → Differential (changes only the range).
Use a pressure gauge to verify settings.
Test the system after adjustments.
Pressure Switch: Simple, on/off control, but causes pressure fluctuations.
VFD: Smooth pressure control, energy-efficient, but more expensive.
A centrifugal pump pressure switch is essential for automating pump operation, ensuring consistent pressure, and preventing damage. Proper adjustment and maintenance are crucial for reliable performance.
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