The Siemens SIRIUS 3RV2921-1M is a signaling switch designed as a direct accessory for 3RV2 motor starter protectors and circuit breakers. It provides separate tripped signal and short circuit alarm contacts, each configured as 1 NO + 1 NC, giving the panel builder two independent status feedback paths from the breaker.
The 3RV2921-1M plugs directly onto the front of 3RV2 breakers in frame sizes S00, S0, S2, and S3. It mounts via plug-in fixing onto the breaker itself. Contact ratings are voltage-dependent. The AC-12 maximum of 10 A (resistive load) is the thermal limit; the real-world signal load is usually lower. At 230 V the switch handles 4 A, at 400 V it's 3 A, and at 690 V it's 10 A — the 690 V figure is the highest voltage class for this auxiliary contact block, so it can be used in 690 V line-to-line control circuits common in European industrial panels. For inductive loads (AC-15 duty, typical for contactor coils), the rating drops to 1 A at 690 V. That means a single 3RV2921-1M can drive one large contactor coil at 690 V, but not two in parallel — the 1 A limit governs the inductive switching life.
Screw-type terminals accept 0.5 to 2.5 mm² solid or stranded, or 2 x (0.5 to 1.5 mm²) and 2 x (0.75 to 2.5 mm²) for looping through. AWG 18 to 14 for the auxiliary circuit. The 18 mm width matches the standard 3RV2 breaker profile — no overhang on the side.