Siemens 3TK2805-0BB4 SIRIUS Safety Contactor Combination for Safety Circuits

The Siemens 3TK2805-0BB4 is a SIRIUS safety relay expansion module, engineered to increase the number of safe outputs in a machine safety system. This contactor combination for safety circuits is designed to work with a basic safety relay to expand its functionality. Operating with a 24V DC rated control supply voltage, the unit provides a high number of enabling contacts for direct switching of actuators.

Contact Configuration and Ratings

The 3TK2805-0BB4 is configured with 5 normally open (NO) enabling contacts and 1 normally closed (NC) signaling contact. The unit has a 75mm width housing. The enabling contacts are used for switching safety-related loads, while the auxiliary signaling contact provides status feedback to a PLC or other monitoring system. The contact arrangement complies with the requirements for safety circuits according to relevant standards.

Safety Integrity and Standards Compliance

The contactor safety combination features a 2-channel redundant design with earth-fault and short-circuit detection. This ensures high reliability and safety in operation and meets the requirements of Performance Level e according to DIN EN ISO 13849-1 and SIL 3 according to DIN EN / IEC 62061. The unit is intended for use in EMERGENCY STOP circuits and in circuits for monitoring protective equipment such as safety guards and protective screens.

Technical Specifications

Rated operational current Ie is 6 A at 40°C and 4 A at 55°C. The contactor combination is designed for control circuits and can be used with various protective devices. The unit is climate-proof and meets the requirements for protection against accidental contact according to DIN VDE 0106 Part 100. When arranged with other equipment, terminal covers must be mounted on the connecting bars. The control circuit coils of 3TK1 contactors can be retrofitted with RC elements. The 3TK10 to 3TK15 contactor coils are designed as draw-out coils.

Applications in Machine Safety

The 3TK2805-0BB4 can be used in EMERGENCY-OFF circuits and for monitoring protective devices, the expansion of safety circuits with additional contact capacity, and integration into higher-level safety architectures with multiple safe switching devices. Typical applications include emergency stop circuits requiring additional safe contact capacity, safety gate monitoring with multiple contactors, machine tool safety systems, and industrial machinery requiring SIL 3 or PL e rated safety components.

Wiring and Installation

The contactor combination features screw terminals for secure field wiring. Internal circuit diagrams for the DC version are provided in the operating instructions. The unit is designed for DIN rail mounting in a control cabinet. Connection examples are illustrated in the product documentation for both one-channel and two-channel configurations. The 2-channel redundant design requires proper interconnection with the base safety unit to maintain the specified safety integrity level.

Conclusion

The Siemens 3TK2805-0BB4 SIRIUS safety contactor combination provides reliable expansion of safe outputs for emergency stop and protective guard circuits. With 5 enabling contacts, 1 signaling contact, and 24V DC operation, it supports safety integrity up to PL e and SIL 3 for industrial machinery automation.