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The Application of NA200 in Constant-Pressure Water Supply Systems for Residential Communities
Release date:
2020-03-31
As people increasingly demand higher quality in water supply and drinking water, the variable-frequency constant-pressure water supply method has emerged. This innovative approach not only effectively addresses the issue of secondary water contamination caused by traditional rooftop tank systems but also optimizes the operation of water pumps—eliminating the inefficiencies associated with adjusting pump speed combined with outlet valve control for regulating water flow and pressure. By doing so, it significantly reduces energy waste that typically occurs due to resistance in the outlet valve, while simultaneously providing excellent protection for the pumps and achieving substantial energy savings. Today, variable-frequency constant-pressure water supply systems are widely adopted in urban municipal water networks, residential community domestic and fire-fighting water systems, building central air-conditioning cooling water circulation systems, and industrial equipment cleaning systems.
As people increasingly demand higher quality in water supply and drinking water, the variable-frequency constant-pressure water supply method has emerged. Not only does it effectively address the issue of secondary water contamination caused by traditional rooftop tank systems, but it also optimizes the operation of water pumps—eliminating the need for outlet valve adjustments to control water flow and pressure. This approach significantly reduces energy waste that traditionally occurs when pumping power is dissipated through outlet valves, while simultaneously providing excellent protection for the pumps and dramatically improving energy efficiency. Today, variable-frequency constant-pressure water supply systems are widely applied across various sectors, including urban municipal water networks, residential community domestic and fire-fighting water systems, central air-conditioning cooling water circulation systems in buildings, and industrial equipment cleaning systems, among many others.
The residential area's variable-frequency constant-pressure water supply system consists of a PLC, a frequency converter, an air pressure tank, a centrifugal pump, and a pressure transmitter. The operational process works as follows: Pressure sensors installed in the pipeline network detect changes in water pressure caused by fluctuations in water consumption, promptly sending these pressure signals back to the PLC. The PLC then performs PID control—comparing the detected pressure with the setpoint—and calculates the necessary adjustments before issuing a frequency conversion command. This command adjusts the operating speed of the water pump, ensuring that the water pressure in the pipeline network remains consistent with the target control pressure.
How it works
When the pressure tank cannot meet the water supply demand, all three pumps will operate at variable frequency. Here's how it works:
First, put pump M1 into variable-frequency operation. If this fails to maintain stable pressure in the pipeline network, switch the original variable-frequency pump M1 to mains frequency while keeping M2 running at variable frequency, ensuring a steady water supply to the network. If both pumps still cannot stabilize the pipeline pressure, activate the standby pump M3 for variable-frequency operation, while M1 and M2 continue running at mains frequency.
When the water level drops, the inverter’s frequency lower-limit signal is triggered, causing the current variable-frequency pump to stop while simultaneously switching the previous unit to variable-frequency operation. If both of these signals persist, the PLC will repeat the process described above.
The system diagram is as follows:
PLC Configuration
The PLC uses the Nanda Aoto NA200 series CPUs—specifically the CPU201-2002 and DOM201-0802. The CPU201-2002 comes equipped with 8 digital input channels, 6 digital output channels, 4 analog input channels, and 2 analog output channels. Additionally, its two built-in communication ports can independently connect to text displays and frequency converters for seamless communication.
The point table is as follows:
PLC Address Function Definition
%I0001 Starts the air pressure tank water supply
%I0002 Manually control pump M1 to operate at variable frequency
%I0003 Manually control water pump M1 at line frequency
%I0004 Manually control pump M2 to operate with variable frequency
%I0005 Manually control water pump M2 to operate at line frequency
%I0006 Manually control the M3 variable-frequency pump to operate
%Q0001 Open the valve to supply water using the air pressure tank.
%Q0002 Starts the Inverter
%Q0003 Pump M1 operates at variable frequency
%Q0004 Pump M1 operates at power frequency
%Q0005 Pump M2 operates with variable frequency
%Q0006 Pump M2 operates at power frequency
%Q0007 Pump M3 operates with variable frequency
%Q0008 Start small pump M4
%MW0001 Pipeline Network Pressure
%MW0003 Inverter Output Frequency
Program Design
NA200Pro software is the IEC61131-3 programming, debugging, and runtime software designed for the NA200 PLC. NA200Pro includes an editor, compiler, debugger, simulator, and graphical user interface tools, primarily used to complete tasks such as hardware configuration, measurement point setup, software programming, simulation, debugging, and downloading.
The NA200Pro offers a comprehensive suite of features that enable higher productivity and enhanced software collaboration capabilities. The NA200Pro software helps optimize customers' software investments by reducing development costs, streamlining operations, and more—while also lowering training expenses and delivering unparalleled potential in terms of development and compatibility.
Summary
NA200's outstanding analog input/output processing capabilities, combined with its built-in PID function, ensure the reliability and stability of constant-pressure water supply systems—also signaling a bright future for domestically produced PLCs in applications within the water supply industry.
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Aoto Technology Co., Ltd.
