Allen-Bradley MSR126.1T 440R-N23114 Safety Relay – Guardmaster Series

Allen-Bradley MSR126.1T 440R-N23114: Dual-Channel Safety Relay for SIL 3 / PLe Machine Guarding Circuits

The Allen-Bradley MSR126.1T, catalogued under part number 440R-N23114, is a hardwired dual-channel safety relay module engineered for monitored emergency stop, interlocked safety gate, and optoelectronic safety device interface applications. Operating at 24 V DC, it achieves the highest functional safety ratings available for discrete relay-based architectures: Safety Integrity Level 3 (SIL 3) per IEC 62061 and Category 4 / Performance Level e (PLe) per ISO 13849-1. These ratings are not marketing designations — they reflect a verified probability of dangerous failure per hour (PFH) below 10⁻⁸, confirmed through TÜV Rheinland third-party certification.

Within a machine control architecture, the MSR126.1T occupies the safety function layer between field-level safety devices (E-stop buttons, gate switches, light curtains) and the machine’s power-interrupting actuators (contactors, drives, pneumatic valves). Its role is to monitor the integrity of the dual-channel input loop, detect cross-faults, short circuits, and welded contacts, and provide a controlled, time-deterministic output response. The module’s 22.5 mm DIN rail footprint integrates directly into standard IEC 60439-compliant control panels without requiring additional mounting hardware.

This product is stocked as genuine OEM hardware sourced through verified supply chains. Each unit ships from Xiamen, China with full documentation including certificate of conformity and original datasheet.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The MSR126.1T implements a redundant relay output architecture using two independent force-guided relay channels. Force-guided (or positively driven) contacts are mechanically linked such that NO and NC contacts cannot simultaneously be in the same state — a welded NO contact physically prevents the NC contact from opening. This mechanical constraint is the hardware basis for the module’s ability to self-detect output contact failure during the next demand cycle, satisfying the diagnostic coverage requirements for Category 4.

Cross-fault detection is implemented at the input stage. The module applies a pulsed test voltage to each input channel independently. If a cross-connection between Channel 1 and Channel 2 exists (e.g., due to cable insulation failure), the pulse timing mismatch is detected within the monitoring window, and the module inhibits the output. This mechanism eliminates the common-cause failure mode where a single wiring fault defeats both channels simultaneously.

EMC design on the MSR126.1T follows IEC 61000-4 series requirements. The input circuitry incorporates transient suppression rated to 1 kV (1.2/50 µs surge) and 2 kV (burst per IEC 61000-4-4). The relay coil drive circuit uses flyback suppression to prevent inductive kickback from coupling into adjacent signal wiring on the DIN rail. This is particularly relevant in panels where the safety relay is mounted adjacent to variable frequency drives or servo amplifiers generating high dV/dt switching transients.

Reset logic is implemented in hardware, not firmware. In manual reset mode, the module requires a deliberate rising edge on the reset input after the safety input channels have returned to the safe state. This prevents automatic restart after a fault clearance — a requirement under ISO 13849-1 for applications where unexpected restart poses a hazard. The absence of a microcontroller in the reset path eliminates software-related common-cause failures from the safety function.

Contact monitoring of the output relays is performed via the NC auxiliary contact feedback loop. When wired into the reset circuit (as recommended in the application wiring diagram), the module verifies that both safety output contacts have opened before permitting a reset. A welded contact on either output relay will prevent the reset input from being acknowledged, holding the system in the safe state and generating a visible fault indication via the LED status display.

System Integration Benefits

• Deterministic response time: The ≤ 20 ms de-energization response is a hardware-guaranteed parameter, not a software-scheduled task. This allows machine designers to calculate worst-case stopping distance with a fixed, bounded safety function reaction time, simplifying ISO 13849-1 performance level verification calculations.
• No firmware dependency: The safety function is implemented entirely in discrete relay logic. There is no embedded software, no firmware update requirement, and no vulnerability to software-related systematic failures (SFF). This simplifies IEC 62061 FMEA documentation for the safety function.
• Plug-compatible with Guardmaster ecosystem: The 440R-N23114 shares terminal assignments and DIN rail footprint with other modules in the Guardmaster family, enabling modular panel design where safety functions can be added or reconfigured without redesigning the panel layout.
• Diagnostic transparency via auxiliary contact: The NC auxiliary output provides a real-time hardware signal reflecting the state of the safety output contacts. This signal can be wired to a standard PLC digital input (e.g., CompactLogix 5380 DI module) to provide safety state visibility in the HMI without routing safety-critical signals through the standard PLC I/O path.
• Dual reset mode flexibility: Jumper-selectable manual/automatic reset allows the same hardware to be deployed in applications requiring supervised restart (manual reset, Category 4) and in applications where automatic restart is permissible after fault clearance (automatic reset, lower-risk zones), reducing SKU proliferation in spare parts inventory.
• Wide operating temperature range: The 0 °C to +55 °C operating range covers the thermal envelope of most enclosed industrial control panels without forced cooling. For panels in high-ambient environments, the module’s low self-heating (≤ 2.5 W) minimizes its contribution to panel thermal load.
• Compact 22.5 mm footprint: In panel designs where DIN rail space is constrained, the 22.5 mm width allows multiple safety functions to be implemented within a single 300 mm DIN rail segment. This is relevant in machine-mounted control boxes where panel volume is a hard design constraint.
• Standards-compliant documentation package: Each unit is supplied with a certificate of conformity referencing the applicable TÜV certification. This documentation is required for CE marking of machinery under the EU Machinery Directive 2006/42/EC and simplifies the technical file compilation for the notified body review process.

Quality Assurance & Global Logistics

Every Allen-Bradley MSR126.1T 440R-N23114 unit offered through this listing is sourced as genuine Rockwell Automation OEM hardware. Units are procured through verified distribution channels with full supply chain traceability. Date codes and lot numbers are recorded at intake. Visual inspection confirms label integrity, connector condition, and packaging authenticity. Anti-static protective packaging is applied to all units regardless of whether original OEM packaging is present.

A 12-month warranty against manufacturing defects is provided on all units. Warranty claims are processed with reference to the recorded lot number and date code. Certificate of conformity and the original Rockwell Automation product datasheet are available upon request at no additional charge.

Logistics operations are based in Xiamen, China. In-stock orders are processed and dispatched within 1–2 business days. International shipments are routed via DHL Express, FedEx International Priority, or UPS Worldwide Expedited depending on destination and customer preference. Export documentation — including commercial invoice, packing list, and certificate of origin — is prepared for all international shipments. HS code 8536.49 applies to safety relay modules for customs classification purposes. Customers in the EU, North America, Southeast Asia, and the Middle East are regularly served from this location with typical transit times of 3–7 business days.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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