Siemens 3RN1010-1CB00 Retrofit-Ready Thermistor Relay for SIRIUS 3RN Control Systems
The Siemens 3RN1010-1CB00 is a thermistor motor protection relay engineered for seamless integration into SIRIUS 3RN series control architectures. As legacy motor protection circuits age and original components reach end-of-life, the 3RN1010-1CB00 serves as a verified drop-in replacement that preserves existing wiring layouts, terminal assignments, and DIN-rail mounting footprints. Whether you are modernizing a 1990s-era motor control center, upgrading a distributed control system panel, or restoring a production line after an unplanned failure, this relay delivers the electrical compatibility and functional parity required to minimize engineering rework and reduce commissioning time.
Rated for 24V AC/DC supply voltage, the 3RN1010-1CB00 accepts PTC thermistor sensor inputs directly from motor windings, providing reliable over-temperature tripping without requiring additional signal conditioning modules. Its compact 22.5 mm housing fits standard S00 contactor mounting positions within SIRIUS control cabinets, making it directly interchangeable with earlier 3RN10 variants and compatible with the broader SIRIUS 3RT contactor and 3RV circuit breaker ecosystem.
Upgrade Compatibility Table
| Parameter | 3RN1010-1CB00 (This Unit) | Retrofit Notes |
|---|---|---|
| Supply Voltage | 24V AC/DC | Verify panel supply rail; replace 3RN1010-1AA00 (230V) if voltage differs |
| Sensor Input | PTC Thermistor (Type A/B) | Compatible with standard 3-wire PTC sensors embedded in motor windings |
| Mounting | DIN Rail / S00 Screw Mount | Direct fit into existing SIRIUS 3RT/3RV mounting positions; no adapter required |
| Output Relay | 1 NO + 1 NC | Map to existing contactor coil circuit; verify terminal A1/A2 polarity |
| Communication | Hardwired (no fieldbus) | For PROFIBUS/PROFINET integration, pair with 3UF7 SIMOCODE module |
| Replacement Models | 3RN1010-1CB00 replaces 3RN1010-1CB00 legacy stock | Also compatible as replacement for 3RN1000-1CB00 in equivalent circuits |
| Commissioning | No software required | Adjust trip threshold via front-panel selector; test with motor at operating temp |
| Warranty | 12 Months | Covers manufacturing defects; includes pre-shipment functional test report |
Retrofit Planning for Existing Automation Systems
Successful integration of the 3RN1010-1CB00 into a legacy motor control system begins with a thorough audit of the existing control cabinet. Engineers should first document the current terminal block layout — particularly terminals T1, T2 (thermistor input) and 95, 96, 97, 98 (output contacts) — to confirm wire gauge compatibility and confirm that existing cable lengths reach the new relay’s screw terminals without splicing. In panels where the original relay was mounted alongside a 3RT1016 or 3RT1017 contactor, the 22.5 mm width of the 3RN1010-1CB00 preserves the original busbar spacing and avoids the need to re-drill the DIN rail.
Power supply verification is critical before energizing the replacement unit. The 3RN1010-1CB00 operates on 24V AC/DC; panels previously running a 3RN1010-1AA00 (230V AC) variant must have the supply circuit modified or a step-down transformer added. In multi-motor control centers, the 24V supply is often shared with 3TK28 safety relays and 3SE5 position switches — confirm that the additional load of the new relay does not exceed the 24V SITOP PSU8200 power supply’s rated output current.
For systems where the motor protection relay interfaces with a SIMATIC S7-300 or S7-1200 PLC via discrete I/O, the output contact state (tripped / healthy) must be mapped to the correct digital input module — typically a 6ES7 321-series DI card. Verify that the PLC program’s fault logic references the correct input address and that the HMI screen (whether a SIMATIC HMI TP700 Comfort or a legacy OP7 panel) displays the correct alarm text for motor over-temperature events. If the original program used a latching fault acknowledgment routine, confirm the reset input wiring to terminal 98 of the new relay is intact.
In distributed control architectures where motor starters are managed through a PROFIBUS DP segment, the 3RN1010-1CB00’s hardwired output can be read by a 3UF7 SIMOCODE pro motor management relay, which then reports status upstream to the S7-400 controller via the DP network. This approach avoids the need to modify the PROFIBUS GSD file or reconfigure the DP master station. For newer installations migrating to PROFINET, the same SIMOCODE pro V PN variant handles the protocol translation transparently.
Backplane and rack considerations apply when the motor protection relay is installed within a modular motor starter combination. In SIRIUS 3RA6 compact starter assemblies, the relay occupies a defined slot position; replacing it requires releasing the bus connector clip and sliding the new unit into the same position without disturbing adjacent 3RA6 I/O expansion modules. Always re-seat the bus connector firmly and verify continuity on the internal communication bus before closing the cabinet door.
Downtime Control During System Migration
Minimizing production downtime during a motor protection relay replacement requires a structured hot-swap procedure. Begin by placing the affected motor circuit in a safe, de-energized state using the upstream 3RV2 motor circuit breaker as the isolation point — do not rely solely on the contactor to isolate the circuit. Photograph the existing terminal wiring before disconnection, and use numbered cable markers on each wire to ensure accurate reconnection to the 3RN1010-1CB00’s terminals.
Where the motor drives a critical process — such as a cooling pump, conveyor, or compressor — coordinate the replacement window with the operations team to align with a scheduled maintenance break. Pre-stage the replacement relay, a calibrated multimeter for thermistor resistance verification, and a copy of the original wiring diagram. The 3RN1010-1CB00 requires no firmware loading or parameter download, which means the physical swap, wiring reconnection, and functional test can typically be completed within 20–40 minutes by a qualified electrician.
After reconnection, perform a cold-start test: energize the 24V supply to the relay, confirm the healthy LED illuminates, and verify that the output contact closes (motor circuit enabled). Then simulate a thermistor fault by temporarily disconnecting the T1/T2 sensor wires — the relay should trip within the specified response time and the contactor should drop out. Re-connect the sensor wires and press the reset button to restore normal operation. Document the test result and retain it alongside the 12-month warranty certificate supplied with each unit.
For plants running continuous processes where even a brief stop is unacceptable, consider pre-wiring the replacement relay on a temporary DIN rail section outside the cabinet, completing all terminal connections in advance, and then performing a rapid swap of the entire sub-assembly. This approach reduces in-cabinet work time to under five minutes and keeps the motor circuit offline for the shortest possible interval.
Retrofit Support FAQ
Q1: Is the 3RN1010-1CB00 a direct replacement for the 3RN1000-1CB00?
Yes. The 3RN1010-1CB00 is the current-generation successor to the 3RN1000-1CB00 and maintains identical terminal assignments, mounting dimensions, and electrical ratings. No wiring modifications are required for a direct swap in existing SIRIUS 3RN panel positions.
Q2: What pre-shipment testing is performed on each unit?
Every 3RN1010-1CB00 supplied by SMARTNEXMSK undergoes a functional energization test verifying supply voltage acceptance, thermistor input response, and output relay operation before dispatch. A test record is included with each shipment. All units carry a 12-month warranty against manufacturing defects from the date of invoice.
Q3: Can this relay be used with NTC thermistors instead of PTC sensors?
No. The 3RN1010-1CB00 is designed exclusively for PTC (Positive Temperature Coefficient) thermistor inputs. For NTC sensor applications or Pt100 RTD-based motor protection, the appropriate replacement is the Siemens 3RN2 series analog temperature monitoring relay, which supports a wider range of sensor types.
Q4: How do I verify compatibility with my existing SIRIUS control cabinet before ordering?
Confirm three parameters: (1) supply voltage — must be 24V AC/DC; (2) sensor type — must be PTC thermistor; (3) output contact configuration — must match your contactor coil circuit requirements (1 NO + 1 NC). If your existing relay carries a different 3RN1010 suffix (e.g., -1AA00 for 230V or -1GW00 for 110–130V), contact [email protected] with your panel drawing for a compatibility assessment before ordering.
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