Siemens 3RH2911-1FA22 — Auxiliary Contact Block Buying Guide

By Abdullah Zahid
11 min read
Siemens 3RH2911-1FA22 snap-on auxiliary contact block for 3RH21 control relay and 3RT201 contactor front-mount expansion

Siemens 3RH2911-1FA22 Auxiliary Contact Block: Specifications, Compatibility and Selection Guide

If you are specifying a contact expansion module for a 3RH21 control relay or 3RT201 contactor installation and have landed on the Siemens 3RH2911-1FA22, you are likely at the final verification stage — confirming contact configuration, current rating, and mechanical compatibility before placing the order. The 3RH2911-1FA22 is a snap-on front-mount auxiliary contact block from the Siemens SIRIUS 3RH2 series, providing a 2NO plus 2NC contact configuration rated at 6A AC-15 and compliant with IEC 60947-5-1. It is designed exclusively for front-mount expansion on 3RH21 and 3RT201 base units — not a universal module.

If you have already confirmed this is the correct part for your system, check current pricing and stock availability at LeadTime.ca — we ship worldwide.

Is the 3RH2911-1FA22 the Right Choice for Your Control System?

This module is the correct choice for engineers and technicians who need to expand auxiliary contact capacity on an existing SIRIUS installation without redesigning the panel or replacing the base unit. It is a good fit when all of the following apply:

  • Your base unit is a 3RH21 control relay or 3RT201 contactor — this block is not compatible with 3RH41, 3RV, or other series
  • Your control circuit voltage is 24V, 230V, 400V, or 690V
  • Your auxiliary circuit load does not exceed 6A AC-15 at 24V, 230V, or 400V (or 3A at 690V)
  • You require exactly 2 normally-open and 2 normally-closed contacts — not a 1NO+1NC arrangement
  • The front surface of your base unit has a clear, undamaged snap-on mounting receptacle at screw terminal positions .1/.2 and .3/.4
  • Your application demands a module rated for 10,000,000 mechanical switching cycles

If you need a 1NO+1NC configuration instead of 2NO+2NC, the correct variant is the 3RH2911-1HA22. If your auxiliary circuit exceeds the 6A AC-15 rating, a higher-rated external auxiliary contactor controlled through this block is the right architecture. If your base unit is not a 3RH21 or 3RT201, a different auxiliary block series applies.

On this page:

What the 3RH2911-1FA22 Actually Does in a Control System

The Siemens 3RH2911-1FA22 is an electromechanical auxiliary contact module that snaps onto the front face of a 3RH21 control relay or 3RT201 contactor to deliver two additional normally-open and two additional normally-closed switching contacts for auxiliary and control circuit use. Its role is purely additive — it expands switching capacity without touching the main power circuit or requiring the base unit to be removed from the panel.

In practice, this means a controls engineer working with an existing 3RH21 installation that was originally specified with limited auxiliary contacts can add status feedback signals, interlock logic paths, or remote monitoring contacts without sourcing a new relay with a higher native contact count. The contacts are screw-terminal connected at positions .1/.2 and .3/.4 on the block face, and the module carries a rated mechanical service life of 10,000,000 switching cycles — meeting the continuous-duty benchmark for industrial control applications.

The identification number 22 on this model is significant: it encodes the contact configuration (2NO+2NC) and must match the compatibility chart in the base unit technical manual. IEC 60947-5-1 compliance confirms this module meets international standards for low-voltage switchgear and control gear, which matters for machinery requiring CE marking across EU and North American markets.

Typical System Architecture: Where This Block Fits

The 3RH2911-1FA22 sits between the control relay or contactor and the downstream auxiliary circuit devices — it is not in the main power path, but in the supervisory and logic layer of the control system.

  • PLC digital output or control voltage source drives the coil of the 3RH21 or 3RT201 base unit
  • The 3RH2911-1FA22 snaps onto the front face of the base unit, mechanically linked to its actuator
  • Terminals .1/.2 and .3/.4 on the auxiliary block connect to downstream auxiliary circuit loads — indicator lights, interlock relay coils, PLC digital inputs, or solenoid valves within the 6A AC-15 current limit
  • When the base unit coil energizes, the auxiliary block contacts change state simultaneously, providing 2NO and 2NC switching paths at the rated voltage
  • Multiple downstream devices such as remote monitoring systems, HMI status inputs, or interlock chains receive discrete contact signals without any connection to the main power circuit

Typical Applications and Deployment Scenarios

The most common deployment of the 3RH2911-1FA22 is in motor control centers and machine control panels where an original relay specification called for fewer auxiliary contacts than a system expansion or retrofit now requires. Automotive and steel plant engineers add these blocks to motor starter contactors in the 3RT201 series to feed multiple PLC inputs simultaneously — one contact for run confirmation, another for fault interlock, a third for remote status, all without touching the main contactor wiring.

Food processing and pharmaceutical facilities use this block in safety interlock chains where machine guard door status or emergency stop feedback must be confirmed across multiple control loops. The 2NO+2NC configuration is particularly useful here because permissive logic and monitoring logic can be wired from the same relay actuation event, reducing relay count in the panel.

OEM machine builders integrate the 3RH2911-1FA22 during panel assembly for pre-engineered control modules that must ship with defined contact counts. The snap-on design and 36mm width allow dense mounting configurations without significant panel space penalties. Field service technicians also stock this block as a replacement module because the snap-on format allows a qualified technician to swap the module in under 10 minutes without panel rewiring.

Application Typical Deployment
Motor control center expansion Status feedback contacts from 3RT201 motor starter contactors to PLC digital inputs
Safety interlock logic Machine guard door monitoring and emergency stop feedback across multiple control loops
Remote monitoring addition Adding discrete contact outputs to existing relays for SCADA or HMI status signals
OEM pre-assembled control panels Dual-circuit supervision modules with defined 2NO+2NC contact count built into machine panels
Retrofit and field replacement Replacing worn auxiliary modules on running 3RH21 installations with no circuit redesign
Two-hand control circuits Implementing multiple supervision contacts from a single relay in press and forming machine applications

Purchase-Decision Specs and How the 3RH2911-1FA22 Compares Within the Family

Specification 3RH2911-1FA22
Contact Configuration 2NO + 2NC
Mechanical Service Life 10,000,000 switching cycles
Rated Current AC-15 at 24V / 230V / 400V 6A
Rated Current AC-15 at 690V 3A
Rated Voltage Range 24V, 230V, 400V, 690V
Minimum Operating Temperature -25°C
Terminal Type Screw terminals at positions .1/.2, .3/.4
Mounting Snap-on front mount
Standards Compliance IEC 60947-5-1
Dimensions (W x H x D) 36mm x 37.5mm x 43.7mm / Weight: 0.056 kg

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

Model Contact Configuration Rated Current AC-15 Compatible Base Units Best For
3RH2911-1FA22 2NO + 2NC 6A (up to 400V), 3A at 690V 3RH21, 3RT201 Applications requiring dual NO and NC switching paths from one relay
3RH2911-1HA22 1NO + 1NC 6A (up to 400V), 3A at 690V 3RH21, 3RT201 Simpler logic requiring fewer contacts; lower-density panel layouts
Other 3RH29 variants Various configurations Varies by model Series-specific Different contact arrangements within 3RH2 family; confirm base unit compatibility

If your control logic requires exactly 2NO+2NC switching from a 3RH21 or 3RT201 base unit, the 3RH2911-1FA22 is the correct choice — check current availability and pricing at LeadTime.ca.

Expert Verdict: Who Should Order This Module and When to Choose Something Else

The 3RH2911-1FA22 earns its place as a standard stock item in any facility running Siemens SIRIUS 3RH21 or 3RT201 equipment. The 10,000,000-cycle mechanical service life is a legitimate reliability benchmark for continuous-duty switching applications, and the snap-on format genuinely changes the maintenance economics — field swap completion in under 10 minutes versus 45 or more minutes for panel-level component changes is a real downtime reduction. The 2NO+2NC configuration covers the majority of auxiliary supervision and interlock wiring scenarios without requiring engineers to build ladder logic workarounds. For OEMs and maintenance teams standardized on the SIRIUS platform, stocking this block is a straightforward decision.

The honest limits are these: if your auxiliary circuit load runs above 6A at 24V, 230V, or 400V, or above 3A at 690V, this module is not the correct switching element and contact welding is a real risk. In those cases, use the 3RH2911-1FA22 contacts to drive a higher-rated auxiliary contactor coil, not the load directly. If your system uses 3RH41 relays, 3RV motor starters, or any base unit outside the 3RH21 and 3RT201 families, this block will not mount — it is not a universal auxiliary module regardless of visual similarity. And if a 1NO+1NC configuration is sufficient for your logic, the 3RH2911-1HA22 is the leaner choice. If this matches your system requirements, view current stock and pricing at LeadTime.ca.

From a procurement standpoint, the 3RH2911-1FA22 is one of the more reliably stocked Siemens SIRIUS components. It is a standard expansion module across automotive, food processing, and discrete manufacturing sectors, which means distributor inventory is typically maintained at depth. Volume pricing improves meaningfully at 10 or more units, making it economical for OEM panel builders to include in build-of-material pricing. Lead times from authorized distributors are generally same-day to two-day for standard quantities, with longer windows possible on combined bulk relay orders.

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

Wiring and Installation Overview

The following is an overview of key requirements for installing the 3RH2911-1FA22. Engineers requiring full step-by-step procedures should refer to the Siemens SIRIUS technical manual for the 3RH21 or 3RT201 base unit.

  • De-energize the base unit and verify 0V at all control circuit terminals with a calibrated test meter before handling the module or touching terminals
  • Align the module contact pins with the snap-on receptacle openings on the relay front face — pins must seat into positions .1/.2 and .3/.4 without cross-threading; apply firm steady pressure until the module snaps flush with no visible gaps
  • Connect auxiliary circuit wiring to screw terminals at .1/.2 and .3/.4, confirming that the incoming voltage matches one of the rated values (24V, 230V, 400V, or 690V) and that the circuit load does not exceed 6A AC-15 at the lower voltages or 3A at 690V
  • Before re-energizing, use an ohmmeter in continuity mode to verify NC contacts show continuity and NO contacts show resistance with the coil de-energized; reverse states confirm correct seating when the coil is briefly energized
  • Cycle the base unit coil three to five times after commissioning to confirm consistent contact state transitions; any intermittent response requires re-inspection of the snap receptacle and pin alignment before returning to service

Wrong-Part Prevention: Critical Compatibility Checklist Before You Order

This checklist should be reviewed against your bill of materials and physical installation before placing any order for the 3RH2911-1FA22. Every item represents a documented ordering or installation error.

  1. Verify base unit is 3RH21 control relay or 3RT201 contactor; 3RH2911 blocks are not universal
  2. Check screw terminal positions on base unit match block terminal layout (.1/.2, .3/.4)
  3. Confirm control circuit voltage rating (24V, 230V, 400V, 690V) against application
  4. Verify contact type requirement: this model provides 2NO+2NC; confirm this matches control logic
  5. Confirm identification number matches relay or contactor series revision compatibility
  6. Check mechanical space for snap-on mounting on relay front surface before ordering

If any item on this checklist raises a question, do not assume — contact the LeadTime.ca team to confirm compatibility before ordering. Returning an incorrect module costs more in downtime than a pre-order verification call.

Frequently Asked Questions

Is the 3RH2911-1FA22 compatible with the 3RT201 contactor series, or only with 3RH21 control relays?

The 3RH2911-1FA22 is compatible with both 3RH21 control relays and 3RT201 contactors. Both base unit types support snap-on front-mount auxiliary blocks from the 3RH29 series. Confirm the snap-on receptacle is present on the specific base unit revision you are working with by checking the relay technical manual or physically inspecting the front face for the receptacle opening.

What happens if I exceed the 6A AC-15 current rating through the auxiliary contacts?

Exceeding the 6A AC-15 rating at 24V, 230V, or 400V will cause accelerated contact wear, pitting, and eventual contact welding or failure. The solution for higher-current auxiliary loads is to use the 3RH2911-1FA22 contacts to drive the coil of a higher-rated auxiliary contactor, with the larger contactor switching the actual load. This keeps the 3RH2911-1FA22 contacts within their rated parameters.

Can I use the 3RH2911-1FA22 in a circuit rated above 690V?

No. The rated voltage for this module is 24V, 230V, 400V, or 690V. Applications with auxiliary circuit voltages above 690V are outside the rated specification for this block. A different module rated for the higher voltage would be required, and the base unit compatibility would also need to be separately verified.

How do I know when the 3RH2911-1FA22 needs to be replaced due to end-of-life wear?

The rated mechanical service life is 10,000,000 switching cycles. In practice, tracking cycle count directly is only feasible in applications with a PLC counting relay actuations. More commonly, maintenance schedules are based on service hours combined with annual contact resistance measurements — rising resistance on a screw terminal connection or intermittent contact operation under normal load are indicators that the module is approaching end of service. Replacement is a snap-on field swap that a qualified technician can complete in under 10 minutes without removing or rewiring the base unit.

Will the identification number 22 always match my 3RH21 relay, or do I need to verify this?

The identification number 22 encodes the 2NO+2NC contact configuration and must be verified against the compatibility chart in your specific 3RH21 or 3RT201 base unit technical manual. While identification number 22 is standard for the 2NO+2NC configuration across the 3RH2 family, different series revisions may have specific requirements. Always cross-reference the identification number in the technical manual before ordering to avoid a non-fitting module on an older or newer base unit revision.

What is the difference between the 3RH2911-1FA22 and the 3RH2911-1HA22?

The 3RH2911-1FA22 provides a 2NO+2NC contact configuration, while the 3RH2911-1HA22 provides a 1NO+1NC configuration. Both are front-mount snap-on blocks compatible with 3RH21 and 3RT201 base units. The choice depends on how many auxiliary switching paths your control logic requires. If your application needs to simultaneously drive a feedback signal and an interlock signal from one relay event, the 2NO+2NC arrangement of the 3RH2911-1FA22 is the more capable choice.

Why Order the 3RH2911-1FA22 from LeadTime.ca

  • LeadTime.ca stocks Siemens SIRIUS components including the 3RH29 auxiliary block series and ships worldwide — no regional restriction on order placement
  • Volume pricing is available for orders of 10 or more units, relevant for OEM panel builders and maintenance stocking programs
  • Hard-to-find or short lead-time parts can be sourced through the LeadTime.ca team directly — contact the team for availability confirmation before committing to a build schedule
  • Response to quote requests is fast — reducing procurement uncertainty for projects with defined commissioning dates

At-a-Glance Summary

  • Model: Siemens 3RH2911-1FA22 — front-mount snap-on auxiliary contact block, SIRIUS 3RH2 series
  • Contact configuration: 2 normally-open (NO) + 2 normally-closed (NC)
  • Rated current: 6A AC-15 at 24V, 230V, and 400V; 3A AC-15 at 690V
  • Mechanical service life: 10,000,000 switching cycles
  • Minimum operating temperature: -25°C
  • Dimensions: 36mm wide x 37.5mm high x 43.7mm deep; weight 0.056 kg
  • Terminal type: Screw terminals at positions .1/.2 and .3/.4
  • Standards compliance: IEC 60947-5-1
  • Compatible base units: 3RH21 control relays and 3RT201 contactors only — not universal
  • Identification number 22 must match base unit compatibility chart before ordering
  • Field replacement time: under 10 minutes with snap-on design; no panel rewiring required
  • Nearest alternative for fewer contacts: 3RH2911-1HA22 (1NO+1NC configuration)