Why Choose the ABB CM-ENS.21P Liquid Level Fill/Drain Monitoring Relay?
The ABB CM-ENS.21P (order code 1SVR740850R0200) is a versatile and reliable liquid level monitoring relay designed for automatic filling and draining control of tanks, reservoirs and industrial liquid handling systems. As part of the ABB CM-ENS measuring and monitoring relay series, it provides dependable monitoring of electrically conductive liquids, helping protect pumps against dry running and storage vessels against overflow.
The CM-ENS.21P uses conductive electrode sensing to detect liquid levels and control connected equipment according to the selected operating mode. Its adjustable sensitivity range of 0.1–1000 kΩ enables adaptation to liquids with different electrical conductivities, while selectable Fill (UP) and Drain (DOWN) functions provide flexibility for automatic liquid level regulation.
With a wide 24–240 V AC/DC control supply, a single changeover relay output and maintenance-free push-in connection terminals, the ABB CM-ENS.21P is suitable for integration into industrial control panels and pump automation systems. Its compact 22.5 mm DIN rail-mounted housing, front-mounted adjustment controls and LED status indicators simplify installation, commissioning and operational monitoring.
Key Advantages
- Reliable automatic liquid level monitoring and control for conductive fluids.
- Selectable filling and draining operating modes for flexible pump control.
- Wide 24–240 V AC/DC supply voltage for compatibility with industrial control systems.
- Adjustable 0.1–1000 kΩ sensitivity accommodates different liquid conductivities.
- Supports pump dry-running protection and tank overflow prevention.
- Easy Connect Technology with push-in terminals enables fast, maintenance-free electrical connections.
- Compact 22.5 mm housing width saves valuable control cabinet space.
- Integrated LED indicators provide convenient visual operating status information.
- Adjustable operating characteristics allow straightforward configuration for different applications.
Key Features
- ABB CM-ENS liquid level monitoring relay series.
- Fill (UP) and Drain (DOWN) operation selectable using a front-face potentiometer.
- 24–240 V AC/DC rated control supply voltage.
- 0.1–1000 kΩ adjustable response sensitivity.
- 1 changeover (SPDT) relay contact for switching external control circuits.
- 250 V AC / 4 A relay contact rating.
- Conductive liquid detection using electrode-based measurement.
- Monitoring of minimum and maximum liquid levels using suitable electrodes.
- Three integrated LEDs for operating status indication.
- Push-in connection technology for efficient control wiring.
- High electromagnetic compatibility for industrial environments.
- Tool-free mounting and removal from standard DIN rails.
- Optional electrode accessories and sealable transparent adjustment cover.
- Compact housing manufactured using flame-retardant material classified UL 94 V-0.
Technical Specifications
- Manufacturer: ABB
- Series: CM-ENS Measuring and Monitoring Relays
- Model: CM-ENS.21P
- ABB order code: 1SVR740850R0200
- Product group: 310921 – Measuring & Monitoring Relays
- Product type: Liquid level fill/drain monitoring relay
- Monitoring function: Conductive liquid level monitoring
- Operating modes: Filling (UP) / Draining (DOWN)
- Rated control supply voltage: 24–240 V AC/DC
- Rated AC supply frequency: 50 / 60 Hz
- Measuring principle: Conductive electrode sensing
- Adjustable sensitivity: 0.1–1000 kΩ
- Liquid level control: Minimum / maximum level monitoring
- Relay output: 1 changeover contact (SPDT)
- Output contact rating: 250 V AC / 4 A
- Terminal technology: Push-in, ABB Easy Connect Technology
- Operating indication: 3 LED status indicators
- Adjustment: Front-face potentiometers
- Housing width: 22.5 mm
- Mounting type: DIN rail mounting
- Protection rating: IP50 housing / IP20 terminals
- Operating ambient temperature: −25 to +60 °C
- Storage temperature: −40 to +85 °C
- Housing flammability classification: UL 94 V-0
- Approximate product weight: 0.117 kg
- GTIN / EAN: 4013614502866
Reliable Liquid Level Control for Industrial Pumping Systems
Liquid level monitoring relays such as the ABB CM-ENS.21P provide automatic control of pumps and liquid handling equipment by measuring the electrical conductivity between electrodes installed at defined liquid levels. When the liquid reaches or falls below the selected electrode positions, the relay changes its output state according to the configured operating mode. This allows connected control equipment to start or stop pumps without requiring continuous manual intervention.
In Fill (UP) mode, the relay can control a filling pump to maintain the liquid between minimum and maximum levels. In Drain (DOWN) mode, it can control an emptying pump to remove liquid when the upper level is reached and stop when the lower level is detected. These functions support reliable tank level regulation while helping prevent overflow and unnecessary pump operation.
The adjustable sensitivity makes the CM-ENS.21P suitable for different electrically conductive liquids, while its wide supply voltage range and push-in terminals simplify integration into existing automation installations. Its compact DIN rail design and clear LED indications make it a practical solution for industrial maintenance engineers, control panel builders and pump system integrators. Suitable sensing electrodes are selected separately according to the liquid and installation conditions.
Typical Applications
- Automatic filling and draining of industrial storage tanks.
- Water reservoir and liquid storage level control.
- Industrial pump control and dry-running protection.
- Tank overflow prevention and high-level monitoring.
- Wastewater collection and drainage systems.
- Sump pump and liquid transfer installations.
- Water treatment and filtration equipment.
- Process tanks containing electrically conductive liquids.
- Industrial machinery requiring automatic liquid level regulation.
- OEM control panels and automated pumping systems.
