Safety output expansion for the 3SK1 series
The Siemens 3SK1211-2BB00 is a SIRIUS safety relay output expansion module — it adds contact capacity to an existing safety relay circuit without duplicating the logic. Rated for 24 V DC control supply, it switches loads up to 5 A per contact at 24 V, 115 V, or 230 V, with a total current limit of 12 A across all contacts. The 22.5 mm width and screw/snap-on mounting let it sit directly on a DIN rail next to the base safety relay, sharing the same enclosure space.
The 5 A contact rating is consistent across 24 V, 115 V, and 230 V AC/DC — so the same module handles control circuits at different voltage levels without derating. The 12 A total current limit means you can parallel contacts for higher load current, but the sum across all switched circuits must stay under that ceiling. Response time is 45 ms typical, 50 ms maximum — fast enough for most safety functions but not for light-curtain applications that need sub-10 ms reaction. The push-in spring terminals accept solid wire 1x (20…16 AWG) or 2x (20…16 AWG), and stranded with ferrule 1x (0.5…1.0 mm²) or 2x (0.5…1.0 mm²), which saves wiring time compared to screw clamps.
Deployment context
As a safety relay output expansion, this module is used in safety circuits guarding hazardous machine zones — press brakes, packaging lines, robotic cells. The -25 to +60 °C operating range and IP20 enclosure suit clean, dry industrial environments; the shock resistance of 10g / 11 ms means it holds up on vibrating equipment like conveyors or punch presses.