Safety monitor for AS-Interface safety at SIL 3 / PL e
The Siemens 3RK1105-1BE04-0CA0 is an ASIsafe Basis safety monitor — a dedicated safety relay module designed to supervise two enabling circuits on an AS-Interface safety network. It carries two fail-safe relay outputs (2 F-RO) and is rated for use up to Category 4 per EN 954-1, PL e per EN ISO 13849-1, and SIL 3 per IEC 61508, making it suitable for guarding hazardous machine zones where a fault must not lead to loss of the safety function. The module's response time is a maximum of 40 ms — fast enough to meet the stop-time requirements of most press, robot cell, and conveyor guarding applications, provided the downstream contactors and actuators are coordinated within that window.
24 V supply and relay contact ratings
The monitor draws 1 A from a 24 V supply for its internal electronics; the relay outputs are rated 3 A at 24 V DC in DC-12 (DC-1) duty and 3 A at 250 V AC in AC-12 duty, 50/60 Hz. These ratings govern the maximum load the safety outputs can switch directly — typically solenoids, contactor coils, or indicator lamps — without an intermediate interface relay. For higher inrush loads or inductive switching, the 3 A continuous rating at 250 V AC sets the ceiling; the 115 V and 230 V auxiliary supply draws (0.1 A and 0.05 A respectively) are for the module's own control circuits, not the load side.
DIN-rail mount, IP20, screw terminals
The IP20 protection class means it is suitable for dry indoor enclosures; no washdown rating, so keep it behind a panel door in wet environments. Inputs and outputs connect via screw terminals (removable on this version), which simplifies wiring and replacement without disturbing the field wiring. The AS-Interface protocol is supported natively — no separate gateway or bus coupler needed for the safety channel.