The Usage Method of the Liquid Level Relay

     The liquid level relay is an automated device used to monitor the liquid level and control the start and stop of equipment (such as water pumps and valves). It is widely applied in scenarios like water tanks, pools, and sewage treatment. The following are its general usage methods and precautions. The specific operations need to be adjusted according to the product model (such as the JD series and YJ series of Chint liquid level relays) and the instruction manual:

I. Basic Principles and Structure

1. Core Functions

The height of the liquid surface is sensed through liquid level sensors (such as float balls, electrodes, and hydrostatic pressure sensors, etc.). When the liquid level reaches the preset thresholds (such as high level and low level), the relay contacts act to control the operation of external equipment (such as water pumps and alarms).

2. Common Types

- **Float Type**: The switch is triggered by the floating of the float ball along with the liquid level (suitable for liquids like water and oil, with strong pollution resistance).

- **Electrode Type**: Utilizes the conductive characteristics of the liquid, and the circuit is conducted through the electrodes contacting the liquid surface (suitable for clean liquids, and measures need to be taken to prevent scaling).

- **Hydrostatic Pressure Type**: The change in the hydrostatic pressure of the liquid level is sensed through a pressure sensor (suitable for closed containers or scenarios with deep liquid levels).

 II. Usage Steps (Taking the Float Type Liquid Level Relay as an Example)

1. Preparation Before Installation

- **Confirm the Scenario**: Clearly define the control requirements (such as "start the water pump for water replenishment at a low liquid level and stop at a high liquid level" or "drain at a high liquid level and stop the pump at a low liquid level").

- **Select the Appropriate Model**: Select the model according to the properties of the liquid (corrosiveness, impurities), the type of container (open/closed), and the number of liquid level control points (single/double/multiple liquid levels).

- **Check the Accessories**: The relay body, float ball sensor, installation bracket, and connection wires (usually a 3-5 core cable, including power supply and contact output wires).

2. Installation and Fixation

- **Sensor Installation**:

  - For Open Containers: Hang the float ball vertically inside the container, ensuring that the float ball can move freely without obstruction, and lead the cable out from the top of the container (to prevent the liquid from seeping into the connection terminals).

  - For Pipeline Installation: Connect the sensor to the side wall of the pipeline through a flange or thread, ensuring that the float ball can float freely with the liquid level.

- **Relay Installation**: Fix it in the control cabinet or a dry and ventilated place, away from high-temperature and humid environments.

3. Wiring Connection

- **Power Supply Wiring**: Connect to the specified power supply such as AC 220V or DC 24V (pay attention to distinguishing the live wire, neutral wire, and ground wire).

- **Contact Wiring**:

  - **Normally Open/Normally Closed Contacts**: Connect the equipment (such as the coil of the water pump contactor) according to the control logic. For example:

    - Start at a Low Liquid Level: When the liquid level is lower than the low level, the normally open contacts of the relay close, and the water pump is started;

    - Stop at a High Liquid Level: When the liquid level reaches the high level, the normally closed contacts open, and the water pump stops.

  - **Multiple Liquid Level Control**: If the relay supports multiple thresholds (such as high, medium, and low liquid levels), different contacts need to be connected correspondingly.

- **Example Wiring Diagram (Taking the Chint JD Series as an Example)**:

  

  (Note: The actual wiring should be based on the instruction manual to avoid short circuits caused by incorrect wiring!)

4. Parameter Setting (If Applicable)

- **Adjustment of the Liquid Level Threshold**: Some models support mechanical adjustment (such as the length of the float ball connecting rod) or electronic setting (set the high and low liquid level trigger points through knobs/buttons).

- **Delay Function**: Enable the anti-misoperation delay (for example, when the liquid level fluctuates, delay for 5-10 seconds before triggering the relay) to avoid frequent start and stop.

5. Debugging and Operation

1. **Inspection Before Powering On**: Confirm that the wiring is firm, there is no short circuit or looseness; the float ball moves smoothly without jamming.

2. **Simulation Test**:

    - Manually lift the float ball to the high level and observe whether the relay contacts open (stop the equipment);

    - Lower the float ball to the low level and check whether the contacts close (start the equipment).

3. **Actual Operation**: Fill water/drain water into the container, and observe whether the equipment starts and stops according to the preset logic, and whether the liquid level is synchronized with the action of the relay.

6. Daily Maintenance

- **Regular Cleaning**: For the float type, remove the impurities attached to the surface (such as oil stains and scale); for the electrode type, wipe the electrodes to prevent scaling from affecting conductivity.

- **Contact Inspection**: Check whether the relay contacts are oxidized or burned, and polish them with fine sandpaper if necessary.

- **Cable Inspection**: Prevent the cable from aging and damage, especially the cable of the sensor that is immersed in the liquid for a long time.

III. Precautions

1. **Safe Operation**: Be sure to cut off the power before wiring or maintenance to avoid electric shock or equipment damage.

2. **Load Matching**: The rated current/voltage of the relay contacts should be greater than the working parameters of the external equipment (such as the water pump), otherwise, a contactor needs to be used in combination.

3. **Environmental Adaptation**:

    - For corrosive liquids, sensors made of anti-corrosion materials (such as stainless steel and plastic) need to be selected;

    - For flammable and explosive scenarios, explosion-proof liquid level relays need to be selected.

4. **Troubleshooting**:

    - If the equipment does not operate: Check whether the power supply is normal, whether the contacts are poorly connected, and whether the sensor is jammed;

    - Frequent start and stop: It may be that the liquid level fluctuates too much, and the delay function needs to be enabled or the installation position of the sensor needs to be optimized.

 IV. Typical Application Scenarios

1. **Water Tank Water Replenishment Control**:

    - When the liquid level is low, the relay contacts close, and the water replenishment pump is started; when the liquid level is high, the contacts open, and the water replenishment stops.

2. **Sewage Tank Drainage Control**:

    - Start the drainage pump when the liquid level is high and stop the pump when the liquid level is low (it can be equipped with a double float ball to achieve automatic circulation).

3. **Equipment Anti-dry Burning Protection**:

    - Monitor the liquid level of the boiler and cooling pool, and trigger an alarm and stop the machine when the liquid level is lower than the safe level.

V. Reference Materials

- Refer to the instruction manuals of specific models (such as Chint JD1, YJ-18, etc.) to obtain the wiring diagrams, technical parameters, and installation dimensions.

- Video Tutorials: Search for practical operation videos such as "Wiring Method of the Liquid Level Relay" and "Wiring of the Water Pump Controlled by the Float Switch" to assist in understanding.

Through the above steps, the correct installation and stable operation of the liquid level relay can be achieved. In case of complex scenarios (such as multi-pump linkage and intelligent control), it is recommended to contact the technical support of the manufacturer or a professional electrician for assistance.