NewTrend · Liquid level control relay
Product overview
NewTrend RL8-03 controls a pump transferring water from a lower well to a raised tank. Separate well and tank electrodes coordinate filling and stop the pump when the well level falls below Min1. Sensitivity is adjustable from 5 to 100 kilohms. A front pushbutton and external start-button connection allow manual starting within the level-control logic. The 18mm DIN-rail relay uses AC/DC 24-240V and provides one SPDT output rated 10A AC-1.
Technical selection summary
| Model | RL8-03 |
|---|---|
| Function | Well-to-tank level control with manual start |
| Control supply | AC/DC 24-240V, 50-60Hz |
| Supply terminals | A1-A2 |
| Power input | Maximum 2VA |
| Supply tolerance | -15% to +10% |
| Electrode terminals | Well: C, Min1, Max1; tank: C, Min2, Max2 |
| Sensitivity (input resistance) | Adjustable 5-100kΩ |
| Electrode voltage | Maximum AC 5V |
| Probe current | AC below 0.1mA |
| Response time | Maximum 400ms |
| Mechanical setting accuracy | 10% maximum |
| Maximum probe-cable length | 800m at 25kΩ sensitivity; 200m at 100kΩ |
| Maximum probe-cable capacitance | 400nF at 25kΩ sensitivity; 100nF at 100kΩ |
| Output contacts | 1 SPDT; 11-12-14 |
| Contact rating | 10A, AC-1 |
| Switching voltage | 250VAC / 24VDC |
| Minimum DC breaking power | 500mW |
| Output indication | Red LED |
| Supply indication | Green LED |
| Manual start | Front pushbutton; external pushbutton connection shown in wiring diagram |
| Mechanical life | 10,000,000 operations |
| Electrical life (AC-1) | 100,000 operations |
| Reset time | Maximum 200ms |
| Operating temperature | -20 to +55 degrees C |
| Storage temperature | -35 to +75 degrees C |
| Mounting | DIN rail to EN/IEC 60715; 18mm module |
| Protection | IP20 terminals |
| Operating position | Any |
| Overvoltage category /pollution degree | III / 2 |
| Maximum conductor size | Solid: 1 x 2.5mm² or 2 x 1.5mm²; with sleeve: 1 x 2.5mm² (AWG 12) |
| Body dimensions | 90 x 18 x 64mm |
| Weight | 80g |
| Referenced standard | EN 60255-1 |
| Overall height in drawing | 95mm including rail-clip projection; body 90mm |
Operation
- When the tank falls below Min2 and the well is above Min1, the relay starts filling until the tank reaches Max2.
- When the well reaches Max1 and the tank is below Max2, the pump starts filling. The original diagram permits leaving Max1 unconnected when this function is not required.
- With the tank between Min2 and Max2, the front or external manual-start button can initiate filling until Max2.
- If the well falls below Min1 during pumping, the relay stops the pump and the red LED flashes to indicate a water shortage.
Typical applications
- Water transfer from wells to elevated storage tanks
- Water-tower filling with separate well and tank level probes
- Pump contactor control requiring low-well-level stop and manual start
View or download RL8-03 well-to-tank level-control catalogue (PDF)
Product reference images and drawings
Original specifications and model coding
Original well/tank function, wiring, panel and dimension drawings
Follow the original well/tank electrode diagram and manual-start wiring. Keep probe-cable length and capacitance within the specified limits. Use a suitably rated external contactor for the pump motor. Body height is 90mm; the original dimension drawing shows 95mm overall including the rail-clip projection. Installation and wiring must be performed by qualified electricians.
