Working principle and function of variable frequency constant pressure water supply system

Working principle and function of variable frequency constant pressure water supply system
The variable frequency constant pressure water supply system is an intelligent water supply equipment that combines variable frequency speed regulation technology with pressure feedback control to achieve automatic adjustment of water supply pressure. It is widely used in residential areas, industrial plants, commercial buildings and other scenarios to solve the problems of unstable pressure and high energy consumption in traditional water supply methods.
1、 Core working principle
The core logic of the system is to set pressure as the target, monitor pipeline pressure in real-time through sensors, and dynamically adjust water pump speed. The specific process is as follows:
Pressure setting and monitoring
Users can set the target pressure value in the control system (touch screen or controller) based on their water demand (such as a water pressure of 0.3MPa on the top floor of residential buildings).
Install pressure sensors (usually diffusion silicon pressure transmitters) in the pipeline network to real-time collect the actual pressure of the water supply pipeline (such as 0.25MPa), and feedback the signal (4-20mA current signal or 0-10V voltage signal) to the variable frequency controller.
Variable frequency speed regulation
Comparison between “actual pressure” and “target pressure” of frequency converter controller (with frequency converter as the core):
If the actual pressure is less than the target pressure (such as during peak water usage periods, when the pressure in the pipeline decreases), the controller outputs a higher frequency power supply (30-50Hz) to drive the water pump motor to increase speed, increase water supply, and improve pipeline pressure;
If the actual pressure is greater than the target pressure (such as during periods of low water usage or when pipeline pressure rises), the controller will reduce the output frequency (5-30Hz), the pump speed will decrease, the water supply will be reduced, and the pressure will fall back to the target value;
If the actual pressure is consistent with the target pressure, the motor maintains stable operation at the current speed.
Multi pump linkage and switching (suitable for high flow systems)
When a single water pump operates at full load (50Hz) but still cannot reach the target pressure (such as during peak water usage), the system automatically starts the second water pump (power frequency or variable frequency start), and multiple pumps are connected in parallel for water supply;
When the water consumption decreases and a single water pump can operate at low frequency to meet the pressure, the system automatically shuts down the excess water pumps to avoid energy waste caused by the “big horse pulling small car”.
Protection and auxiliary functions
Water shortage protection: Monitor the water level of the water source (such as a water tank) through a liquid level sensor, automatically stop the water pump when there is a water shortage, and prevent the water pump from running idle and burning out;
Overload protection: When the motor current exceeds the rated value, the frequency converter automatically shuts off for protection;
Sleep wake-up: When the nighttime water consumption is extremely low (pressure is consistently higher than the target value), the system enters “sleep mode” (shutting down the water pump and relying on residual pressure in the pipeline to supply water), and automatically wakes up when the water consumption recovers.

2、 Core components of the system
Component function
Water pumps provide water supply power (mostly centrifugal pumps, with materials such as cast iron and stainless steel selected according to water quality)
Variable frequency drive adjusts motor speed (core component, controls speed by changing power frequency)
Pressure sensors monitor pipeline pressure in real-time and provide feedback signals to the controller
PLC/controller receives sensor signals, compares target pressure, sends speed control instructions to the frequency converter, and controls multi pump switching
Touch screen/operation panel to set target pressure, display operating parameters (pressure, frequency, flow rate, etc.), manual operation interface
Pipelines and valves connect water pumps and pipelines, including check valves (to prevent water backflow), gate valves (for maintenance purposes), etc
Auxiliary protection devices include liquid level sensors (water shortage protection), current transformers (overload protection), and pressure gauges (visual display)
3、 Main function
Constant pressure water supply enhances the water experience
No matter how the water consumption changes (such as morning and evening peak or late night trough), the system always stabilizes the pipeline pressure at the set value (such as 0.3MPa), avoiding the problem of “insufficient water pressure at high floors and excessive water pressure at low floors” in traditional water supply methods, and ensuring the normal operation of water equipment such as faucets and water heaters.
Energy conservation and consumption reduction, lowering operating costs
In traditional water supply systems (such as water tanks and pumps), the pumps operate at full power frequency, and excess pressure is consumed through valve throttling, resulting in extremely high energy consumption;
The frequency conversion system adjusts the speed (the motor power is proportional to the third power of the speed), reducing the speed when the water consumption is small, and significantly reducing energy consumption (usually saving 30% -50% energy), especially suitable for scenarios with large water waves.
Extend equipment lifespan and reduce maintenance costs
Soft start of water pump (frequency converter starts from zero frequency, no surge current), avoiding the impact of high current on the motor and water pump during traditional direct start, reducing mechanical wear and electrical faults;
Automatic sleep mode and multi pump rotation operation function, balancing the working time of each water pump and extending the overall service life.
Automated operation reduces manual intervention
The system automatically adjusts pressure, switches water pumps, and responds to faults (such as automatic shutdown alarm due to water shortage) without the need for dedicated personnel, saving labor costs;
Support remote monitoring (optional communication module), operation and maintenance personnel can view the operating status in the central control room and promptly handle any abnormalities.
Adapt to complex scenarios and flexibly expand
Flexible configuration of single pump and multi pump systems based on water usage (such as 2 main pumps+1 backup pump);
Suitable for multiple water sources (tap water, water tanks, wells), it can be linked with secondary water supply equipment and water treatment systems to meet the needs of different scenarios such as residential areas, factories, hotels, etc.

4、 Typical application scenarios
Secondary water supply in residential areas: solving the problem of insufficient water pressure in high-rise residential buildings, replacing traditional water tank water supply (reducing the risk of secondary water pollution);
Industrial production water supply: providing stable pressure process water for production lines, cooling towers, etc., to ensure production continuity;
Commercial buildings: hotels, shopping malls, office buildings, etc., meet the stable water supply needs of multiple floors and multiple water points;
Agricultural irrigation: Based on the irrigation pressure requirements of different crops, accurately control the pressure of the pipeline network to save irrigation water.
summarize
The variable frequency constant pressure water supply system achieves stable and energy-saving operation of water supply pressure through closed-loop control of “pressure feedback variable frequency speed regulation”, which not only improves water comfort, but also reduces energy consumption and maintenance costs. It is the core equipment of modern water supply systems, especially indispensable in scenarios with complex water demand and high energy-saving requirements.