Siemens 3RN1010-1CB00 Replacement for SIRIUS 3RN

Product Overview

Siemens 3RN1010-1CB00 Replacement for SIRIUS 3RN: Smooth Transition & Legacy System Compatibility

The Siemens 3RN1010-1CB00 is a thermistor motor protection relay from the SIRIUS 3RN series, designed to evaluate PTC (Positive Temperature Coefficient) thermistor sensors embedded in motor windings. Operating on a wide supply voltage of 24V AC/DC, this relay provides reliable overtemperature protection for three-phase and single-phase motors across a broad range of industrial applications — from pump stations and compressor rooms to conveyor systems and HVAC control panels.

For facilities currently running legacy motor protection schemes based on older bimetallic overload relays, standalone thermistor evaluation units, or discontinued motor management modules, the 3RN1010-1CB00 represents a direct, low-disruption upgrade path. Its compact 22.5 mm housing fits standard DIN rail mounting, making it physically compatible with most existing control cabinet layouts without requiring panel modifications or additional mounting hardware.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful motor protection upgrade rarely involves a single component. When migrating from an older motor control scheme to a modern SIRIUS-based architecture, the 3RN1010-1CB00 typically works in conjunction with several complementary components that must be evaluated for compatibility during the retrofit project.

In most motor starter panels, the thermistor relay is wired in series with the control circuit of a Siemens 3RT2 contactor — the primary switching device for the motor. If the existing contactor is a legacy 3RT1 or older 3TF series unit, this is an ideal time to upgrade to a current-generation 3RT2015 or 3RT2016 contactor, which shares the same mounting footprint and terminal layout, minimizing rewiring effort.

Upstream of the contactor, a Siemens 3RV2 motor circuit breaker provides short-circuit and overload protection. In older installations, this function may have been handled by a separate fuse block and a standalone overload relay such as the 3UA or 3RB series. Replacing these with a coordinated 3RV2 + 3RN1010-1CB00 combination simplifies the protection scheme, reduces panel wiring complexity, and ensures full coordination between thermal and thermistor-based protection.

For applications where the motor is controlled via a Siemens SINAMICS G120 or G120C variable frequency drive, the thermistor relay output can be wired into the drive’s digital input for motor overtemperature fault signaling. This integration eliminates the need for a separate motor management relay and allows the drive to respond directly to PTC sensor trips — a common requirement in pump and fan retrofit projects where energy efficiency and motor longevity are priorities.

In larger motor control centers (MCCs) built around Siemens SIRIUS modular system components, the 3RN1010-1CB00 can be mounted directly alongside 3RP15 timing relays, 3RS10 temperature monitoring relays, and 3UG48 voltage monitoring relays on the same DIN rail section, maintaining a consistent 22.5 mm module grid. This uniformity is particularly valuable when retrofitting existing panels where space is constrained and cable routing is already established.

Where the existing installation uses a Siemens ET 200S or ET 200SP distributed I/O station for remote motor monitoring, the relay output of the 3RN1010-1CB00 can be wired into a digital input module — such as the 6ES7131-4BF00-0AA0 for ET 200S or the 6ES7131-6BF01-0BA0 for ET 200SP — allowing the PLC program to log thermistor trip events, generate maintenance alarms, and implement automatic restart logic without modifying the motor protection relay itself.

For facilities upgrading from standalone relay panels to a fully integrated Siemens S7-1200 or S7-300 PLC-based control system, the thermistor relay’s discrete output integrates directly into the existing I/O architecture. No special function blocks or firmware updates are required — the relay behaves as a standard digital input signal, making it fully compatible with existing ladder logic or FBD programs developed in STEP 7 or TIA Portal.

Retrofit Guidance FAQ

Q: Can the 3RN1010-1CB00 replace a bimetallic overload relay directly?
A: Not as a direct functional substitute — bimetallic relays respond to current, while the 3RN1010-1CB00 responds to PTC thermistor resistance. However, if the motor already has embedded PTC sensors (standard on most IEC motors manufactured after 2000), the 3RN1010-1CB00 can replace the overload relay’s thermal protection function while providing more accurate, sensor-based temperature monitoring. The existing overload relay should be retained for current-based short-circuit coordination unless replaced by a 3RV2 motor circuit breaker.

Q: Is rewiring required when replacing an older 3RN1010 variant?
A: For direct 3RN1010 series replacements (e.g., 3RN1010-1BW00 → 3RN1010-1CB00), the terminal layout is identical. Supply voltage wiring must be verified — the -1CB00 suffix designates 24V AC/DC supply. If the existing installation uses a 110V or 230V supply variant, a control transformer or supply voltage change is required.

Q: What communication protocols does this relay support?
A: The 3RN1010-1CB00 is a hardwired relay — it does not support PROFIBUS, PROFINET, IO-Link, or any fieldbus protocol natively. Its output is a standard SPDT relay contact (1 NO + 1 NC) that integrates with any PLC digital input module or hardwired control circuit.

Q: How much panel space does this relay require?
A: The relay occupies 22.5 mm of DIN rail width and approximately 90 mm in height. This is narrower than many legacy thermistor evaluation units, often freeing up space for additional components during panel upgrades.

Q: Can this relay be used with NTC sensors instead of PTC?
A: No. The 3RN1010-1CB00 is designed exclusively for PTC thermistors conforming to DIN 44081 and DIN 44082. For NTC or PT100/PT1000 sensor applications, a different temperature monitoring relay such as the Siemens 3RS10 series should be selected.

Warranty Assurance

Every Siemens 3RN1010-1CB00 supplied by TOPNLMS is covered by a 12-month warranty from the date of shipment. Prior to dispatch, each unit undergoes functional verification including supply voltage input testing, PTC sensor circuit resistance threshold confirmation, and output relay contact continuity checks. Units that do not meet Siemens factory specifications are quarantined and not shipped.

In the event of a confirmed defect within the warranty period, TOPNLMS provides direct replacement support — no third-party RMA routing, no extended processing delays. Replacement units are dispatched from our Xiamen warehouse, with express shipping options available for urgent production line requirements. Our technical team is available to assist with installation verification, wiring diagram review, and compatibility confirmation before and after purchase.

For bulk procurement, project-based orders, or scheduled delivery programs, please contact our sales team directly. We maintain stock of the full SIRIUS 3RN series to support ongoing maintenance and retrofit programs.