Siemens 3rh2911-1ha11

By Abdullah Zahid
12 min read
Siemens 3RH2911-1HA11 front-mount auxiliary switch block 1 NO 1 NC snap-on for SIRIUS contactor

Siemens 3RH2911-1HA11 Auxiliary Switch Block, Front Mount 1 NO + 1 NC: Specifications, Selection Guide, and Alternatives

Controls engineers specifying a Siemens SIRIUS contactor often reach a familiar decision point: the main device has one auxiliary contact, but the control logic demands two independent feedback states. The Siemens 3RH2911-1HA11 is a snap-on front-mount auxiliary switch block that adds exactly one normally open (NO) and one normally closed (NC) contact to an existing 3RH or 3RT series contactor — without replacing the main device, without rewiring the power circuit, and without adding a separate relay. With a 10,000,000 mechanical duty cycle rating and IEC 60947-4-1 mirror contact compliance, it is a purpose-matched accessory for engineers who need reliable dual-state feedback fast.

If you have already confirmed this is the correct part for your application, check current pricing and availability of the 3RH2911-1HA11 at LeadTime.ca — ships worldwide.

Who Should Buy the 3RH2911-1HA11 — and Who Shouldn't

This block is the right choice if your application checks all of the following boxes:

  • Your contactor is a Siemens 3RH or 3RT series S00 size device with a compatible screw terminal front-mount interface
  • You specifically need a 1 NO + 1 NC contact configuration — not 2 NO, 2 NC, or a three- or five-contact block
  • Your control circuit operates within the AC-15 rated range: 6 A at 24 V or 230 V, 3 A at 400 V, or 1 A at 690 V — or within the DC-12 or DC-13 ratings
  • Screw terminal connections (up to 2.5 mm² conductor) are acceptable in your panel design
  • The installation environment stays within -25°C to +60°C and IP20 enclosure protection is sufficient
  • You require IEC 60947-4-1 mirror contact compliance for interlocking or status monitoring logic

If you need more than two auxiliary contacts, a side-mount orientation, or push-in pluggable terminals, this SKU is not the correct fit. Higher-contact-count blocks (Ident. Nos. 40 to 02) and lateral-mount variants are available as separate models in the SIRIUS accessory line.

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What the 3RH2911-1HA11 Actually Does in a Control System

The 3RH2911-1HA11 is a control circuit accessory, not a standalone switching device. It attaches to the front face of a Siemens 3RH or 3RT series S00 contactor and mechanically mirrors the contactor's main contact state — delivering one normally open and one normally closed auxiliary output to the control circuit simultaneously. When the main contactor energizes, the NO contact closes and the NC contact opens. When it de-energizes, both return to their default states. This is the IEC 60947-4-1 mirror contact definition: the NO and NC states are always mutually exclusive, with no ambiguous intermediate condition.

The block is IEC 60947-5-1 compliant for positively driven operation when used with 3RH2 contactors, meaning the mechanical linkage between the main contact and the auxiliary contact is direct and verifiable. That makes this block suitable for interlocking logic, contactor status monitoring, and sequential control schemes where you need confirmed feedback rather than inferred state. At 10,000,000 rated mechanical duty cycles, it handles continuous or high-frequency switching duty without requiring periodic maintenance or contact replacement. The sealed snap-on assembly is non-repairable by design — if contacts fail, the block is replaced as a complete unit.

One aspect that trips up buyers: this block expands control circuit capability only. It does not carry main circuit current, does not affect the contactor's power switching ratings, and cannot substitute for a separate safety relay in SIL-rated circuits. Its role is feedback and interlocking signal routing within the auxiliary control voltage circuit.

Where This Block Sits in a Typical Control Architecture

The 3RH2911-1HA11 sits directly on the front face of the main contactor and feeds discrete status signals back to the control layer. Here is how the signal chain typically looks in deployment:

  • PLC digital output or control relay → coil of Siemens 3RH or 3RT series S00 contactor
  • Main contactor power contacts → motor, pump, fan, or load device
  • 3RH2911-1HA11 snap-on block → mechanically linked to main contactor armature
  • NO contact (.1/.2 terminals) → PLC digital input or downstream enable circuit
  • NC contact (.3/.4 terminals) → alarm circuit, inhibit signal, or interlock relay coil

Typical Applications and Deployment Scenarios

In pump and motor sequencing applications, the NO contact enables a downstream load only after the main contactor confirms engagement, while the NC contact simultaneously cuts the signal to an unload or backflow valve. This two-state handshake prevents simultaneous operation and avoids water hammer damage in fluid systems.

For backup generator transfer logic, the NO contact monitors utility contactor closure before allowing load transfer, and the NC contact inhibits the generator start signal while the utility contactor remains active. This prevents generator backfeed and paralleling faults without requiring additional relay hardware.

In conveyor and process interlock designs, the 1 NO + 1 NC configuration supports dual-channel architecture for contactor heartbeat monitoring. A PLC can use the NO contact to confirm upstream conveyor engagement and the NC contact to immediately halt downstream sections on de-energization, enabling conditional activation logic with a single accessory block.

Fan and compressor duty cycle monitoring benefits from the mirror contact guarantee — if the contactor fails to energize or fails to release, the NC contact state change triggers an alarm condition without requiring a separate feedback relay or I/O card.

Application Typical Deployment
Pump start/stop interlock NO enables downstream pump; NC cuts backflow valve signal on contactor de-energization
Motor soft-start feedback NO confirms main contactor engagement before soft-starter receives run command
Generator transfer logic NO confirms utility contactor; NC inhibits generator start while utility is active
Sequential conveyor control NO enables downstream motor; NC halts line on upstream contactor drop-out
Fan/compressor monitoring NC state change triggers alarm if contactor fails to energize or de-energize
Batch process automation Dual-state feedback to PLC for conditional recipe step sequencing

Electrical and Physical Specifications Worth Knowing Before You Order

Specification Value
Contact Configuration 1 NO + 1 NC (mirror contact, IEC 60947-4-1)
Mechanical Duty Cycles 10,000,000
AC-15 Rated Current 6 A @ 24 V / 230 V; 3 A @ 400 V; 1 A @ 690 V
DC-12 Rated Current 10 A @ 24 V; 4 A @ 110 V
DC-13 Rated Current 10 A @ 24 V; 1 A @ 110 V
Insulation Voltage 690 V rated; 6 kV surge impulse
Operating Temperature -25°C to +60°C
IP Rating IP20
Dimensions (W × H × D) 36 mm × 37.5 mm × 43.7 mm
Terminal Type / Conductor Screw terminals; up to 2.5 mm² conductor cross-section

Full technical specifications are available on the product page at LeadTime.ca.

3RH2911-1HA11 vs. Alternative Auxiliary Blocks: Which One Do You Actually Need?

Model Contact Config Mechanical Life Mount Type Terminal Type AC-15 @ 24 V Platform
3RH2911-1HA11 1 NO + 1 NC 10,000,000 cycles Front-mount snap-on Screw 6 A Siemens 3RH/3RT S00
3RH2911 higher Ident. Nos. (e.g., 3–5 contact blocks) 3 or 5 contacts Verify datasheet Front-mount snap-on Screw Verify datasheet Siemens 3RH/3RT S00
3RH2921-1HA11 Different config — verify datasheet Verify datasheet Verify orientation Screw Verify datasheet Siemens SIRIUS
Telemecanique LA1KN11 1 NO + 1 NC Comparable — verify Different interface Screw Comparable — verify Schneider platform only
Telemecanique LADN11 1 NO + 1 NC Verify datasheet Different interface Screw Verify datasheet Schneider platform only

The key selection constraint is the mounting interface: Telemecanique blocks such as the LA1KN11 and LADN11 are functional equivalents in contact configuration and current rating, but they are not mechanically interchangeable with the Siemens 3RH/3RT snap-on front-mount interface. Verify the mounting face before substituting across platforms. If your architecture uses a Siemens 3RH or 3RT S00 contactor with the standard front-mount interface, the 3RH2911-1HA11 is the correct choice — check current availability at LeadTime.ca.

Expert Verdict: Honest Assessment for Engineers and Procurement Specialists

The 3RH2911-1HA11 does one thing with high confidence: it reliably adds 1 NO + 1 NC mirror contact feedback to an existing Siemens SIRIUS contactor at the lowest possible cost and installation effort. The 10,000,000 mechanical duty cycle rating is not marketing language — it reflects a sealed, mechanically simple assembly that has been qualified for continuous industrial use. The snap-on installation requires no tools and no main contactor removal, which matters in retrofit and maintenance scenarios where downtime is a real cost. For plant engineers and integrators working with 3RH or 3RT series S00 contactors, this is a straightforward, low-risk specification decision.

Where this block has genuine limits: IP20 protection means it cannot be used in washdown environments or unsealed outdoor panels without additional enclosure protection. There is no pluggable terminal option in this SKU, which matters to OEM designers who standardize on push-in connectors. And if your logic requires three or more auxiliary contacts, this block requires pairing with higher-count SIRIUS accessory blocks — it does not expand beyond 1 NO + 1 NC by itself. For SIL-rated safety circuits, this block is a general-purpose auxiliary contact; dedicated safety relay hardware with certified redundant contact voting is required for functional safety applications. If your application sits at the edge of the AC-15 derating curve — particularly at 400 V or 690 V — calculate your load current with a 1.25 safety margin before committing to this contact size.

From a procurement standpoint, the 3RH2911-1HA11 is an active product in the Siemens SIRIUS line with no announced obsolescence. The Siemens MFN is 100241914 and the alternate catalog format 3RH29111HA11 (no dashes) refers to the same part. The SIRIUS accessory line is widely stocked globally, and standard lead times from major distributors in North America run 1–3 business days. OEM and integrator accounts ordering 5 or more units typically qualify for volume pricing. Adding this block costs a fraction of replacing the entire contactor with a higher-contact-count model — a full contactor upgrade requires complete re-wiring of the power circuit, whereas this block installs in under 30 minutes. If this matches your system requirements, view current stock and pricing at LeadTime.ca.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

Installation and Wiring Overview for the 3RH2911-1HA11

The 3RH2911-1HA11 is designed for tool-free snap-on installation. Before mounting, confirm the following and follow the manufacturer's full installation documentation for complete wiring procedures:

  • Confirm the contactor is a 3RH or 3RT series S00 size with accessible front-mount face and .1/.2 (NO) and .3/.4 (NC) screw terminal positions available
  • Align the block on the contactor front face and press firmly until the snap-on interface seats fully; the centrally arranged release lever locks the block in place — no tools required
  • Strip conductor insulation and insert wires into the appropriate screw terminals: NO contact uses .1 and .2 terminals; NC contact uses .3 and .4 terminals; conductor cross-section up to 2.5 mm²
  • Verify control circuit voltage against the applicable duty cycle rating (AC-15, AC-14, DC-12, or DC-13) and confirm load current does not exceed the rated value at that voltage
  • To remove the block, press the release lever or checkered surface area on the front-mount assembly — do not force or pry the block off, as the snap-on design is a mechanical interference fit

What Engineers Get Wrong When Ordering This Part

Before placing an order for the 3RH2911-1HA11, work through this checklist verbatim. Each item represents a real sourcing or installation failure mode:

  1. Verify contactor model is 3RH or 3RT series S00 size with compatible screw terminal layout (.1/.2, .3/.4 terminals)
  2. Confirm 1 NO + 1 NC contact configuration is required (not 2 NO, 2 NC, or higher-count blocks)
  3. Check that 10,000,000 mechanical life cycle requirement is met (not for extremely low-cycle or one-time applications)
  4. Validate rated current at actual control voltage (AC-15 at 24V: 6A max; at 230V: 6A max; at 400V: 3A max; at 690V: 1A max for AC-15 duty)
  5. Ensure -25°C to +60°C operating temperature suits the installation environment
  6. Confirm screw terminal connection is acceptable (no pluggable connector available on this block)

If any item on this checklist does not match your application, do not order until you have resolved the conflict. Contact the LeadTime.ca team to confirm the correct variant before purchase — or review the full product specifications on the product page.

Frequently Asked Questions

Is the 3RH2911-1HA11 compatible with all Siemens 3RT contactors?

The 3RH2911-1HA11 is compatible with Siemens 3RH and 3RT series S00 size contactors that have the standard front-mount snap-on interface and screw terminal layout (.1/.2, .3/.4 positions). Compatibility is limited to S00 size devices with Ident. Nos. 10 or 01 (one existing auxiliary contact). Contactors with four main contacts and no front-mount auxiliary interface will not accept this block without verification — always confirm the specific contactor model's terminal layout against the accessory datasheet before ordering.

What is the rated current of the 3RH2911-1HA11 at 230 V AC control voltage?

Under AC-15 duty (standard control circuit with AC inductive loads), the 3RH2911-1HA11 is rated at 6 A at 230 V. At 400 V, the AC-15 rating derate to 3 A, and at 690 V it reduces further to 1 A. Always select the applicable duty cycle (AC-15, AC-14, DC-12, or DC-13) based on your actual load type, not just voltage, and apply a 1.25 safety margin to your load current before confirming the block is adequately rated.

Can the 3RH2911-1HA11 be used in a safety-rated interlock circuit?

The 3RH2911-1HA11 meets IEC 60947-4-1 mirror contact requirements and IEC 60947-5-1 positively driven operation standards when paired with 3RH2 contactors, which provides a level of contact state assurance suitable for general industrial interlocking. However, this block is a general-purpose auxiliary contact and is not independently certified for SIL-rated functional safety circuits. For applications requiring SIL or safety integrity compliance, use redundant blocks with certified voting logic or dedicated safety relay hardware.

Does the 3RH2911-1HA11 have an IP67 or washdown rating?

No. The 3RH2911-1HA11 carries an IP20 rating, which provides finger-touch protection against contact with live parts but offers no protection against liquid ingress. It is not suitable for direct washdown environments or unsealed outdoor installation without an additional sealed enclosure rated for the ambient conditions. For food and beverage or pharmaceutical washdown zones, verify that the panel enclosure provides the required protection level around the contactor and auxiliary block assembly.

What is the difference between catalog number 3RH2911-1HA11 and 3RH29111HA11?

These are the same physical part. The format 3RH29111HA11 is an alternate notation without hyphens, used by some distributors and procurement systems. The Siemens official catalog number is 3RH2911-1HA11, and the Siemens MFN is 100241914. When searching distributor databases or cross-referencing purchase orders, both formats should return the same product record.

How long does it take to install the 3RH2911-1HA11, and are special tools required?

Physical mounting requires no tools — the snap-on design seats onto the contactor front face by hand pressure until the release lever locks. Terminal wiring requires a standard flathead screwdriver for the screw terminals and a wire stripper. A typical installation including mounting, wire connection, and verification takes under 30 minutes for a technician familiar with the 3RH or 3RT contactor family. Full installation and wiring procedures are provided in the Siemens product documentation available through the Siemens Image Database or your distributor.

Why Order the 3RH2911-1HA11 From LeadTime.ca

  • LeadTime.ca ships worldwide — no geographic restriction on order fulfillment
  • The 3RH2911-1HA11 is an active Siemens SIRIUS product; LeadTime.ca sources hard-to-find and standard-stocking automation components across the full SIRIUS accessory line
  • Volume pricing is available for OEM and integrator accounts — contact the team directly for orders of 5 or more units
  • Fast response on lead time confirmation before you commit to a build schedule

At-a-Glance Summary

  • The Siemens 3RH2911-1HA11 adds 1 NO + 1 NC mirror contact to a Siemens 3RH or 3RT series S00 contactor via snap-on front-mount attachment
  • Rated for 10,000,000 mechanical duty cycles — no maintenance required; non-repairable assembly
  • AC-15 current rating: 6 A at 24 V and 230 V; 3 A at 400 V; 1 A at 690 V
  • DC-12 rating: 10 A at 24 V; DC-13 rating: 10 A at 24 V
  • Insulation voltage: 690 V rated; 6 kV surge impulse
  • Operating temperature: -25°C to +60°C; IP20 protection rating
  • Dimensions: 36 mm × 37.5 mm × 43.7 mm; weight: 0.11 lbs (approximately 50 g)
  • Screw terminals only; conductor cross-section up to 2.5 mm²; no pluggable connector option
  • Complies with IEC 60947-4-1 (mirror contact) and IEC 60947-5-1 (positively driven operation with 3RH2)
  • Siemens catalog number: 3RH2911-1HA11; alternate format: 3RH29111HA11; MFN: 100241914; active lifecycle status
  • Adding this block avoids full contactor replacement — lower cost, no power circuit rewiring, under 30-minute installation