Analysis of VFD Booster Pump System
Your VFD booster pump, even in a backup mode running **10 minutes every hour**, benefits significantly from the recommended system components, although their roles are slightly adjusted due to the VFD and the timed cycling.
Variable Frequency Drive (VFD)
The VFD is **essential** (since you already have one) for **Soft Start/Stop** functionality. This slow ramping up and down minimizes electrical and mechanical stress, significantly reducing wear and tear on the pump, motor, and pipes, and preventing **water hammer** during the timed start/stop cycle.
Pressure Tank
A small pressure tank is **highly recommended**. Its main purpose in a VFD system is to act as a **hydraulic buffer** to absorb pressure spikes (water hammer) and stabilize minor pressure fluctuations immediately downstream of the pump, resulting in smoother operation.
Pressure Switch (Sensor)
You do not need a traditional mechanical pressure switch. Instead, a **Pressure Sensor (Transducer)** is **essential**. It connects directly to the VFD controller, providing continuous pressure readings so the VFD can accurately modulate the motor speed during the 10-minute cycle to maintain a precise, constant pressure output.
In conclusion, while the VFD reduces the need for a large tank, a small tank and a pressure sensor are crucial for efficiency, protection, and constant pressure delivery during the pump's run time.