Understanding Constant Pressure VFD Water Supply Systems

Product Principle: 

During normal operation, the pressure sensor installed on the main outlet pipeline of the system performs data sampling on the user-side water supply pressure. It converts the pressure signal into an electrical feedback signal and transmits it to the Programmable Logic Controller (PLC). The PLC compares and calculates this feedback value against the user-defined target pressure, then converts the result into two signals: a frequency regulation signal and a pump operation quantity signal, both sent to the Variable Frequency Drive (VFD). The VFD adjusts the frequency of the pump motor accordingly, which in turn controls the pump rotational speed.

When the variable-speed pump runs at the upper frequency limit and the target pressure is achieved, the system will stage an additional pump after a time-delay verification. When the variable-speed pump operates at the lower frequency limit and the actual pressure still exceeds the set value, the system will destage a pump after the same time-delay confirmation. Through the continuous speed regulation of variable-frequency pumps and the step regulation of power-frequency pumps, the water pressure in the user pipe network is stabilized at the pre-set value. This matches the water output of the pump set with the fluctuating water consumption of the pipe network, fulfilling the goal of variable-frequency constant-pressure water supply.

Product Feature:

(1) Pressure adjustment

Pressure can be adjusted up and down by touch within the performance curve range of the water pump

(2) Automatic shutdown when no water is needed

Built in PID constant pressure controller, the system can automatically shut down after 20 seconds without water, and the pressure will not deviate from the set value by 1% after shutdown.

(3) Normal water usage

When the system pressure is lower than 10% of the set pressure, the water pump will start automatically to maintain constant pressure water supply.

(4) Water leakage detection compensation function, power outage without stopping water supply

When encountering a small water leakage in the system, the water pump will only start to compensate for the pressure when the pressure drops to 65%, in order to avoid frequent starting during water leakage

(5) Water shortage and pressure loss protection function

When the pressure of the water pump cannot reach 60% of the set value even after running at full speed, the water pump will automatically stop running after 20 seconds. This function will only take effect after more than one minute of power transmission.