1. Overview

This manual describes the RS485 communication protocol and settings for the pump controller, supporting Modbus RTU communication.
The communication interface allows centralized monitoring, control, and interconnection of multiple pumps for coordinated operation.

2. Communication Interface

• Communication Protocol: Modbus RTU
• Physical Interface: RS485, half-duplex
• Supported Baud Rates: 9600 / 19200 / 38400 bps (default 19200)
• Data Format: 8 data bits, 1 stop bit, no parity
• Address Range: 0–255 (default 3)

Each pump has a unique device ID (B1) for communication on the RS485 bus.

3. Setting Parameters

Parameter	Description	Range / Options	Default
B1	Device ID number	0–255	3
B2	Baud rate	0: 9600  1: 19200 2: 38400	1 (19200 bps)
B3	Communication Mode	0: Stand-alone 1: Master 2: Slave	0 (Normal)
B4	Operating Mode	0: Parallel Constant Pressure 1: Rotation Constant Pressure 2: Parallel Constant Speed 3: Rotation Constant Speed	0
B5	Pump Switching Time	1 = 10 min (Max 99 = 990 min)	User defined

4. Connection Setup

When B3 (Communication Mode) is set to 1 (Master) or 2 (Slave), the operating mode (B4) determines how the pumps coordinate.
Default mode is 0: Parallel Constant Pressure.

Steps to Set Up Interconnection:

1. Assign one pump as Master (B3 = 1) and another as Slave (B3 = 2).
2. Keep both pumps with default Device ID (B1 = 3) unless specific addressing is required.
3. When communication starts, indicator lights on both panels flash.
   • Communication is successful only when both master and slave LEDs flash simultaneously.
4. The slave pump receives its pressure signal from the master pump, so ensure the master’s pressure sensor works correctly.

5. Operation Modes

(1) Parallel Constant Pressure Mode

• Both master and slave pumps boost pressure simultaneously.
• The slave pump’s speed follows the master’s output.
• The master controls pressure to maintain the setpoint.

(2) Rotation Constant Pressure Mode

• Pumps alternate operation based on the set rotation time (B5).
• When switching, the new pump starts first; the running pump delays stopping to ensure stable transition.

(3) Parallel Constant Speed Mode

• Both pumps operate at the same speed.
• Used where pressure feedback is unnecessary or fixed-speed operation is desired.

(4) Rotation Constant Speed Mode

• Pumps alternate running at fixed speed.
• During transitions, the incoming pump starts first, then the other stops after a delay.

6. Communication Function Codes (Modbus RTU)

Function Code	Description	Example
0x03	Read Holding Registers	Read data such as frequency, current, voltage, status, etc.
0x06	Write Single Register	Modify single parameter (e.g. start/stop command).
0x10	Write Multiple Registers	Modify multiple parameters at once.

Common Registers (Example)

Address	Function	Data Type	Description
0x0001	Start/Stop Command	16-bit	1 = Start, 0 = Stop
0x0002	Set Frequency	16-bit	0–5000 (represents 0–50.00Hz)
0x0003	Output Frequency	16-bit	Real-time output frequency
0x0004	Output Current	16-bit	Real-time current (×0.1A)
0x0005	Output Voltage	16-bit	Real-time voltage (×1V)
0x0006	Fault Code	16-bit	See fault table below
0x0007	Operating Mode	16-bit	0–3 per B4

7. Faults and Alarms

If the pump encounters faults such as phase loss, stall, overcurrent, or start failure, it will attempt to auto-restart up to five times.
After five failed attempts, manual intervention is required to reset.

During multi-pump operation:

• Faulty pumps will be automatically bypassed.
• The remaining pump(s) will continue operation independently.

8. Example: Modbus Command Frame

Example 1: Read Register

Request:
01 03 00 01 00 01 D5 CA
(Read one register from address 0x0001)

Response:
01 03 02 00 01 B8 88
(Reply: register value = 0x0001 → pump running)

9. Troubleshooting

Symptom	Possible Cause	Solution
Communication failure	Wrong device ID / baud rate mismatch	Check B1 & B2 settings
Slave not responding	Incorrect communication mode	Ensure Master = 1, Slave = 2
Inconsistent speed	Faulty master pressure feedback	Verify master sensor
Frequent switching	Short rotation time (B5 too small)	Increase rotation time

10. Version Information

Added in this version:

• RS485 communication support (Master/Slave configuration)
• Parallel and rotation operation modes
• Pump interconnection via Modbus RTU
• Auto-fault isolation and retry mechanism
• Adjustable pump rotation time (B5)
• Baud rate configuration (B2)