Why Choose the ABB CM-MSS.22P Thermistor Motor Protection Relay?
The ABB CM-MSS.22P (1SVR740700R0200) is a reliable thermistor motor protection relay designed to monitor motor winding temperature and help protect industrial electric motors against overheating. Part of the ABB CM-MSS monitoring relay range, it works with built-in PTC thermistor sensors to detect excessive motor temperatures caused by overload, insufficient cooling or abnormal operating conditions.
Operating from a 24 V AC/DC control supply, the CM-MSS.22P features one PTC sensor measuring circuit and two changeover (SPDT) output contacts rated at 250 V / 4 A. The relay operates according to the closed-circuit principle and provides configurable automatic, manual or remote reset options, allowing its response to be adapted to different industrial motor control requirements.
The CM-MSS.22P uses ABB's Easy Connect Technology with push-in terminals, enabling fast, secure and maintenance-free electrical connections without conventional screw terminal tightening. Its compact 22.5 mm DIN rail housing, front-mounted reset button and clear operating status indication make it an effective choice for motor control centres, industrial machinery and electrical automation cabinets.
Key Advantages
- Reliable motor winding temperature monitoring using PTC thermistor sensors.
- Helps protect electric motors against overheating, overload and insufficient cooling.
- 24 V AC/DC control supply suitable for industrial automation circuits.
- One PTC sensor measuring circuit for direct motor temperature supervision.
- Two changeover (SPDT) output contacts rated at 250 V / 4 A.
- Configurable automatic, manual or remote reset after the fault condition has cleared.
- Closed-circuit operating principle supports dependable motor protection signalling.
- Easy Connect push-in terminals simplify wiring and reduce installation time.
- Front-mounted reset button allows convenient local operation.
- Overvoltage-protected supply and measuring inputs.
- Designed in accordance with IEC 60947-8 for thermistor motor protection applications.
- Compact 22.5 mm housing width conserves space inside motor control panels.
- Tool-free DIN rail mounting and removal.
- Flame-retardant housing material classified UL 94 V-0.
- Optional sealable transparent cover helps protect against unauthorised adjustments.
Key Features
- ABB CM-MSS.22P thermistor motor protection relay.
- Manufacturer order code: 1SVR740700R0200.
- Rated control supply voltage: 24 V AC/DC.
- Monitoring function: Motor winding temperature monitoring.
- Sensor technology: PTC thermistor temperature sensors.
- Measuring circuits: 1 sensor circuit.
- Reset functions: Automatic, manual or remote reset.
- Local reset: Front-mounted reset button.
- Operating principle: Closed-circuit principle.
- Output configuration: 2 changeover (SPDT) contacts.
- Output contact rating: 250 V / 4 A.
- Connection technology: Easy Connect push-in terminals.
- Overvoltage-protected supply and measuring inputs.
- Motor protection functionality according to IEC 60947-8.
- Operating and relay status indication.
- Housing width: 22.5 mm.
- Tool-free DIN rail mounting and removal.
- Flame-retardant housing classified UL 94 V-0.
- Compatible with an optional sealable transparent protective cover.
Technical Specifications
- Manufacturer: ABB
- Product series: CM-MSS
- Model: CM-MSS.22P
- ABB order code: 1SVR740700R0200
- ABB product group: 310921-Measuring & Monitoring Relays
- Product type: Thermistor motor protection relay
- Rated control supply voltage: 24 V AC/DC
- Monitoring function: Motor winding temperature monitoring
- Sensor type: PTC thermistors
- Number of sensor circuits: 1
- Reset modes: Automatic, manual or remote
- Local reset facility: Front-mounted reset button
- Operating principle: Closed-circuit principle
- Output contacts: 2 changeover (SPDT) contacts
- Contact rating: 250 V / 4 A
- UL/CSA contact rating: B300
- Maximum output operating voltage (UL/CSA): 300 V AC
- Terminal type: Easy Connect push-in terminals
- Connection method: Screwless spring-clamp connection
- Supply and measuring input protection: Overvoltage protected
- Supply and measuring circuit isolation: Not electrically isolated
- Product standard: IEC 60947-8
- Mounting type: DIN rail mounting
- Housing flammability classification: UL 94 V-0
- Operating ambient temperature: −25 to +60 °C
- Storage temperature: −40 to +85 °C
- Dimensions (H × W × D): 85.6 × 22.5 × 103.7 mm
- Net weight: 0.121 kg
- EAN: 4013614496608
- Customs tariff number: 85364900
Reliable Thermistor-Based Motor Temperature Protection
The ABB CM-MSS.22P provides direct thermal monitoring of electric motors by supervising the resistance of PTC thermistor sensors installed within the motor windings. As the winding temperature approaches the sensor's rated response temperature, the thermistor resistance increases sharply. The relay detects this change and switches its output contacts to indicate an overheating condition.
Unlike protection methods based solely on motor current, thermistor-based temperature monitoring measures the motor's actual thermal condition. This helps detect overheating caused by mechanical overload, insufficient ventilation, high ambient temperature, frequent starting or other operating conditions that may not be fully represented by electrical current measurements alone.
The CM-MSS.22P features one PTC sensor measuring circuit and operates according to the closed-circuit principle. When a monitored motor reaches an excessive temperature, the relay can provide a signal to a suitable motor contactor, PLC or alarm system so that corrective action can be taken. The device is intended for use with compatible PTC thermistors rather than standard resistive temperature sensors such as Pt100 probes.
A key advantage of the CM-MSS.22P is its configurable reset functionality. Automatic reset allows the relay to return to its normal state after the fault condition clears. Manual reset requires deliberate operator intervention, while remote reset supports integration with an external control circuit. The appropriate reset mode should be selected according to the machinery's safety and operating requirements, particularly where unexpected motor restarting must be prevented.
The relay also incorporates overvoltage-protected supply and measuring inputs and is designed according to IEC 60947-8, the product standard for control units used with built-in thermal protection in rotating electrical machines. The supply and measuring circuits are not electrically isolated, so installation must follow the manufacturer's wiring and insulation requirements.
ABB's Easy Connect Technology provides screwless push-in terminals for fast, reliable and maintenance-free wiring. Combined with its compact DIN rail housing, two changeover contacts and accessible reset button, the CM-MSS.22P offers a practical solution for protecting industrial motors against damaging thermal conditions.
Typical Applications
- Motor winding temperature protection in industrial machinery.
- Thermal overload monitoring for motors equipped with PTC thermistors.
- Overheating protection in industrial motor control centres.
- Pump motor temperature supervision and dry-running-related overheating detection.
- Fan and ventilation motor thermal monitoring.
- Compressor motor temperature protection.
- Conveyor and material handling motor protection.
- Manufacturing and production equipment motor monitoring.
- Industrial automation systems with PLC-based motor fault signalling.
- Motor control panels using 24 V AC/DC control supplies.
- OEM machinery with integrated thermistor motor protection.
- Industrial processes requiring manual or remote fault reset.
- Applications requiring temperature-based protection alongside conventional electrical motor protection devices.
