Product Overview
The Siemens 3RH1921-1HA22 is a SIRIUS-series auxiliary switch block (also called auxiliary contact block) designed as a left-side snap-on accessory for Siemens 3RT10/3RT11 power contactors and 3RH11 contactor relays in size classes S00, S0, S2 and S3. The “21” in the type code denotes side-mount attachment for the S00–S3 envelope, and “HA22” defines the contact configuration: 2 normally-open (NO) + 2 normally-closed (NC) poles, four contacts total in a single compact block, with screw terminals (the “A” after “H” = screw; “C” would be spring-cage). The Siemens 3RH1921-1HA22 is the most common 4-pole aux-block SKU in the SIRIUS S00–S3 range because it gives both make-and-break feedback (NO mirrors contactor coil energise) and safety/interlock contacts (NC for stop-chain, reverse-interlock, star-delta transition) in one click-on block, instead of stacking two 2-pole blocks.
Mounting is tool-free: the Siemens 3RH1921-1HA22 clips onto the left-hand side of the host contactor or contactor relay, guided by the moulded tongue-and-groove that Siemens standardises across the 3RT10/3RH11 S00–S3 family. Once snapped, the block’s internal actuating pusher couples mechanically to the contactor’s moving armature, so the auxiliary contacts follow the main contacts with <10 ms differential — fast enough for motor-feedback, star-delta transition timing and safety-chain logic. The block adds approximately 18 mm to the contactor’s overall width, stays within the same DIN-rail footprint, and carries IP20 finger-safe terminal shrouds per IEC 60947-5-1.
Electrical rating aligns with SIRIUS aux-block standard: AC-15 at 230 V / 3 A, DC-13 at 24 V / 1 A (typical, exact per Siemens SIRIUS manual for 3RH19 21-series), with a mechanical lifecycle of 10 million operations (typical for SIRIUS Agastat-grade contacts) and an electrical lifecycle that scales with load. The Siemens 3RH1921-1HA22 can be combined with a front-mount aux block (3RH19 31xx series) on the same contactor if the pole count needs to grow beyond 4 — e.g. a star-delta starter may carry one 3RH1921-1HA22 (2NO+2NC) on the star-contactor and another on the delta-contactor, plus a front block on the main for “contactor picked up” feedback to the PLC. For maintenance teams, the Siemens 3RH1921-1HA22 is a <€15 insurance spare that turns a “contactor OK but aux-feedback dead” call-out into a 30-second snap-swap instead of a full contactor replacement — relevant in MCC rooms where the 3RT10 is 45 kW+ and the aux block is the only failed element.
Technical Specifications
| Parameter | Value |
|---|---|
| Product Model | Siemens 3RH1921-1HA22 |
| Manufacturer | Siemens (Germany) |
| Product Type | Auxiliary Switch Block (Side-Mount), 4-Pole |
| Series | SIRIUS 3RH19 |
| Contact Configuration | 2 NO + 2 NC (2 N/O + 2 N/C) |
| Terminal Type | Screw terminal (HA = screw; CA variant = spring-cage) |
| Mounting | Snap-on, left side of contactor (tool-free) |
| Compatible Contactors | Siemens 3RT10 / 3RT11, size S00, S0, S2, S3 |
| Compatible Contactor Relays | Siemens 3RH11 (size S00–S3) |
| Rated Operational Current (AC-15, 230 V) | 3 A (typical, per 3RH19 S00–S3 datasheet) |
| Rated Operational Current (DC-13, 24 V) | 1 A (typical) |
| Mechanical Life | 10 million operations (typical) |
| Electrical Life | Dependent on load category (AC-15 / DC-13) |
| Width Added to Contactor | ~18 mm |
| Degree of Protection | IP20 (finger-safe terminals) |
| Operating Temperature | –25 °C to +60 °C |
| Storage Temperature | –55 °C to +80 °C |
| Standards | IEC 60947-5-1, EN 60947-5-1, CCC |
| Combinability | Can combine with front-mount 3RH19 31xx block on same contactor (pole count limit per size) |
| Weight | ~0.04 kg |
| Related Alternative | 3RH1921-1CA22 (same 2NO+2NC, spring-cage terminal) |
Main Features and Advantages
2NO+2NC in a single side block:
Most S00–S3 contactor applications need at least one NO (coil-feedback to PLC: “contactor picked up”) and one NC (reverse-interlock, stop-chain, star-delta break-before-make). But once you’re doing star-delta, or a forward-reverse, or a pump with “run” + “fault” + “local/remote” feedback, 1NO+1NC runs out fast. The Siemens 3RH1921-1HA22 gives 2NO+2NC in one side block — four poles, one click, one order code. Compare to the 1NO+1NC base block (3RH1921-1HA00) or the 2NO-only (1HA10) or 2NC-only (1HA20): the 1HA22 is the densest single-block SKU, and it’s the one most MCC builders standardize on because it covers 90% of S00–S3 aux needs without stacking.
Tool-free snap-on, SIRIUS mechanical commonality:
The Siemens 3RH1921-1HA22 clips onto the left side of any 3RT10/3RH11 S00–S3 unit — S00 (3RT1015/1016), S0 (3RT1023/1024/1025), S2 (3RT1035), S3 (3RT1045/1046) — same block, same part number, no size-split. That’s a spare planner’s win: one Siemens 3RH1921-1HA22 covers the whole S00–S3 contactor bin, instead of a different aux block per frame size. The snap is audible (click), the internal pusher self-aligns to the contactor armature, and removal is a flat-blade screwdriver under the release tab — no screws, no lost parts.
Screw-terminal (HA) vs. spring-cage (CA) choice:
The “-1HA22” suffix = screw. Siemens offers the identical 2NO+2NC in spring-cage as 3RH1921-1CA22. Screw is still the MCC default (electricians carry Pozidriv #2, not a spring-cage insert-tool), and the Siemens 3RH1921-1HA22 screw terminals accept 0.75–2.5 mm² rigid/flex, torqued 0.8–1.2 Nm typical. In high-vibe environments (crusher MCC, compressor skid, marine) some plants migrate to the CA22 spring version, but the HA22 remains the volume SKU. The screw clamp is nickel-plated, corrosion-resistant, G3-class ambient fine.
10 M mechanical life, IP20 finger-safe:
The SIRIUS Agastat-derived contact design gives the Siemens 3RH1921-1HA22 a 10 M-operation mechanical life — meaning the aux block can outlive the contactor’s main power contacts 2–3× over. The IP20 terminal shrouds satisfy EN 60204 (machine directive) finger-test without add-on terminal covers, and the block sits inside the contactor’s overall envelope so the MCC vertical busbar gutter clearance isn’t disturbed. For OEM panel builders, the Siemens 3RH1921-1HA22 is a “drop-in, don’t think” item on the BOM — Siemens’ EPLAN macros and TIA Selection Tool both have it pre-parameterised.