Siemens 3ra1921-1da00

By Abdullah Zahid
12 min read
Siemens 3RA1921-1DA00 SIRIUS link module connecting S00 contactor to S0 motor protector in industrial panel

Siemens 3RA1921-1DA00 Link Module — Electrical and Mechanical Connector for 3RV2.1/3RV2.2 and 3RT2.1 AC and DC Operation

If you are building or maintaining a Siemens SIRIUS motor control assembly and need the right interconnect between a Size 00 contactor and a Size 0 motor protector, the 3RA1921-1DA00 is the part that closes that gap. This wiring module provides both the electrical and mechanical link between a 3RT2.1 S00 contactor and a 3RV2.1 or 3RV2.2 S0 motor protector or circuit breaker — eliminating separate junction blocks and reducing panel footprint to a compact 45 mm W x 70.3 mm D x 42.7 mm H. The screw terminal construction supports AC and DC operation, making it suitable for the vast majority of SIRIUS motor control configurations currently in service.

If you have already confirmed this is the right part for your contactor and protector combination, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the 3RA1921-1DA00 — and Who Shouldn't

This link module is the correct choice for engineers and technicians assembling or repairing SIRIUS motor control panels built around Siemens S00/S0 component pairings. Buy this part if all of the following are true for your application:

  • Your contactor is a 3RT101 or 3RT2.1 series rated Size 00 (S00)
  • Your motor protector or circuit breaker is from the 3RV1.2, 3RV2.1, or 3RV2.2 series rated Size 0 (S0)
  • Panel space can accommodate 45 mm width, 70.3 mm depth, and 42.7 mm height
  • Your wiring scheme uses screw terminal terminations, not spring-type connectors
  • Your motor control circuit operates on AC or DC — both are supported

If your contactor is a larger size (S2, S3) or belongs to a different product family such as 3RT1 legacy series, the 3RA1921-1DA00 will not mechanically or electrically fit. Contact LeadTime.ca to confirm the correct link module part number for your specific combination.

On this page:

What the 3RA1921-1DA00 Actually Does in a Motor Control System

The 3RA1921-1DA00 is a wiring module that physically and electrically connects a Siemens SIRIUS S00 contactor to an S0 motor protector or circuit breaker, forming an integrated motor starter assembly without requiring intermediate terminal strips or hard-wired junction boxes. It belongs to the SIRIUS modular control component family, and its specific function is to bridge the size mismatch that occurs when a 3-pole Size 00 contactor (3RT2.1 or 3RT101) is paired with a Size 0 motor protective device (3RV2.1, 3RV2.2, or 3RV1.2). The module is rated for both AC and DC operation and uses screw terminals throughout.

The practical value here is not just convenience — it is compliance and reliability. The screw terminal construction performs reliably in industrial vibration environments, and the Siemens-certified interface between these SIRIUS components ensures the assembly meets the same regulatory acceptance as individually certified devices. For panel builders working under UL, CE, or EAC compliance requirements, a certified inter-component connector is not optional.

The module itself weighs 0.03 kg and occupies 45 mm of panel width. Compared to the alternative of external junction blocks with discrete wiring, this approach measurably reduces both the physical footprint and the number of connection points that need to be inspected during maintenance. For facilities that have standardized on the Siemens SIRIUS platform across multiple machines, holding a small inventory of 3RA1921-1DA00 units reduces emergency repair time when motor starters fail unexpectedly.

Where the 3RA1921-1DA00 Sits in a Typical SIRIUS Architecture

This link module occupies the interconnect position between the motor protective device and the switching contactor — the two components that together form a complete motor starter assembly. Understanding its position in the component chain clarifies why getting the right link module matters before any other assembly step begins.

  • Upstream: Upstream power source or bus connects to the 3RV2.1 or 3RV2.2 S0 motor protector or circuit breaker for overload and short-circuit protection
  • At this module: The 3RA1921-1DA00 mechanically and electrically bridges the S0 motor protector to the S00 (3RT2.1 or 3RT101) contactor below it
  • Downstream contactor: The 3RT2.1 S00 contactor switches power to the motor load on command from the control circuit
  • Load side: Motor terminals receive switched power from the contactor output; auxiliary contacts on the contactor feed status signals back to the control system
  • Control wiring: Separate AC or DC control circuit energizes the contactor coil independently of the power path through the link module

Which Industries and Panels Use This Link Module

The 3RA1921-1DA00 appears most frequently in motor control centers and standalone panel assemblies for pump, fan, conveyor, and compressor drive circuits where compact panel density is a design constraint. Automotive OEM production lines and Tier 1 supplier facilities have used this module in SIRIUS motor control assemblies for over 15 years, and the modular replacement capability — swapping a failed link module without re-engineering the entire starter — directly reduces unplanned downtime on high-utilization production equipment.

In food and beverage and pharmaceutical applications, the multi-agency certification coverage (CE, EAC, ABS, Bureau Veritas, PRS, RINA) means the assembly can be accepted in regulated environments without additional compliance testing. This is a meaningful time-saver during commissioning audits in facilities where every installed component requires documented certification status.

Water treatment facilities frequently use S00/S0 SIRIUS assemblies for small pump motor circuits, and the 3RA1921-1DA00 is the standard interconnect in those builds. Mining and chemical processing applications where vibration and harsh environment operation are concerns benefit from the screw terminal construction over spring-type alternatives.

Application Typical Deployment
New motor control panel build Integrating 3RT2.1 S00 contactor and 3RV2.1 S0 protector into a compact starter assembly
Legacy system retrofit Replacing a failed 3RA1921-1DA00 in an existing SIRIUS installation to restore motor control
Emergency maintenance Same-day replacement of link module after motor starter failure on production equipment
Automotive OEM production line Multiple motor starter assemblies using SIRIUS S00/S0 pairings for conveyor and press circuits
Water treatment pump control Small pump motor circuits using 3RV2.1 protector and 3RT2.1 contactor in compact panel
Pharmaceutical or food facility Certified motor starter assemblies requiring documented CE, EAC, and Bureau Veritas compliance

Specifications Engineers Need Before Ordering

Specification Value
Physical Dimensions 45 mm W x 70.3 mm D x 42.7 mm H
Weight 0.03 kg
Connection Type Screw Terminal
Number of Poles 3
Operation AC and DC
Contactor Size Class S00 (Size 00)
Motor Protector Size Class S0 (Size 0)
Country of Origin Germany
Product Family Siemens SIRIUS
Product Category Wiring Module / Link Connector

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

3RA1921-1DA00 Compatibility: Contactors, Protectors, and Circuit Breakers

Getting the compatible contactor and protector combination right before ordering is the single most important step with this part. The table below reflects the verified compatibility matrix for the 3RA1921-1DA00.

Compatible Contactor Series Compatible Motor Protector / Circuit Breaker Series Notes
3RT101 (S00 Size) 3RV1.2 (S0 Size) Electrical and mechanical compatibility verified
3RT2.1 (S00 Size) 3RV2.1 (S0 Size) Primary application; supports AC and DC
3RT2.1 (S00 Size) 3RV2.2 (S0 Size) Compatible; newer 3RV2.2 version supported
3RT2.1 (S00 Size) 3RV2.1 (S00 Size) Cross-size compatible with S00 circuit breaker
3RT2.1 (S00 Size) 3RV2.2 (S00 Size) Cross-size compatible with S00 circuit breaker

If your build uses a 3RT2.1 S00 contactor paired with a 3RV2.1 or 3RV2.2 S0 protector, the 3RA1921-1DA00 is the confirmed correct interconnect — check current availability at LeadTime.ca.

Certifications and Compliance — What Gets Accepted Where

The 3RA1921-1DA00 carries a notable range of third-party certifications, which matters most when the assembled motor control system must pass facility compliance audits or be accepted for export. CE certification covers European Union regulatory requirements, and EAC approval extends acceptance across Eurasian markets. For marine and offshore applications, ABS (American Bureau of Shipping), Bureau Veritas, PRS, and RINA approvals allow the module to be specified in shipboard or offshore installations without separate certification testing. RoHS compliance is confirmed for facilities with materials restriction requirements.

Certification Status
CE Mark Certified
RoHS Compliance Compliant
EAC (Eurasian Conformity) Approved
ABS (American Bureau of Shipping) Approved
Bureau Veritas Certified
PRS Certified
RINA (Italian Ship Register) Certified

Pricing Tiers, Volume Breaks, and Lead Time Reality

The 3RA1921-1DA00 is a low-cost accessory component, with single-unit pricing at $30.32 USD and volume breaks that begin at 10 units. For panel builders or facilities purchasing for multiple machine builds, the pricing structure is meaningful: quantity breaks occur at 10, 25, 50, 100, and 250 units, with the per-unit price dropping to $22.74 USD at 250+ quantity. The table below shows current representative pricing tiers.

Quantity Unit Price (USD) Total Range (USD)
1–9 units $30.32 $30.32 – $272.88
10–24 units $28.81 $288.10 – $691.44
25–49 units $27.29 $682.25 – $1,317.04
50–99 units $25.78 $1,289.00 – $2,552.22
100–249 units $24.26 $2,426.00 – $6,049.74
250+ units $22.74 $5,685.00+

In-stock units at major distributors ship in less than 5 business days. For emergency maintenance situations where a failed link module is holding up production, confirming in-stock status before placing the order is the critical first step. LeadTime.ca ships worldwide — view current stock and pricing here.

Expert Verdict: When This Part Is Right and When It Isn't

The 3RA1921-1DA00 is a well-defined, single-purpose component that does exactly one job — and does it reliably when the contactor and protector combination matches the compatibility matrix. The screw terminal construction is the right choice for industrial vibration environments, and the 45 mm footprint genuinely reduces panel real estate compared to external junction box alternatives. For any facility that has standardized on the Siemens SIRIUS platform and regularly builds or maintains motor starter assemblies using 3RT2.1 S00 contactors and 3RV2.1 or 3RV2.2 S0 protectors, this is the correct interconnect — no investigation needed. The multi-agency certification coverage (CE, EAC, ABS, Bureau Veritas, PRS, RINA) removes compliance friction in regulated industries and export markets. If this matches your system requirements, view current stock and pricing at LeadTime.ca.

Where this part does not belong: if your contactor is a legacy 3RT1 series rather than 3RT2.1 or 3RT101, the mechanical interface will not match and the module should not be forced into place. If your facility has standardized on spring terminal technology rather than screw terminals, a different connector configuration is required. And if your contactor size is S2 or larger, this module is physically the wrong size — the 3RA1921-1DA00 is strictly S00 contactor to S0 protector. These are not edge cases; they are the most common ordering errors in the field, and getting it wrong means a panel that cannot be assembled or a motor circuit that does not make reliable contact.

From a procurement standpoint, this is a low-cost item that rarely requires approval cycles, but it is often the component that holds up a motor starter build when it is missing from inventory. Standard in-stock lead time is under 5 business days through authorized distributor channels. For volume orders supporting facility-wide machine retrofit programs, volume pricing breaks at 10, 25, 50, 100, and 250 units make bulk procurement straightforward 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.

Wiring and Installation Overview

The following points cover the key requirements and verification steps for installing the 3RA1921-1DA00. Engineers requiring full wiring diagrams and step-by-step assembly procedures should refer to the Siemens SIRIUS product documentation available from support.industry.siemens.com.

  • De-energize and lock out the motor control circuit before beginning any installation or replacement work — verify absence of voltage with a calibrated meter before touching any terminals
  • Position the link module between the 3RT2.1 S00 contactor and the 3RV S0 motor protector, ensuring vertical alignment to avoid mechanical stress on the connection interface
  • Screw terminals are the sole connection method — strip wire insulation to the depth specified in the manufacturer documentation, insert wire fully, and tighten using a compatible screwdriver without applying excessive torque that could strip the internal thread
  • If replacing an existing module, photograph the existing wiring configuration before disconnecting to preserve reference for re-termination
  • After installation, verify no exposed conductors are visible at any terminal and that all wires resist a gentle pull-test — a loose screw terminal in this position can cause intermittent motor control faults that are difficult to diagnose remotely

Wrong-Part Prevention Checklist Before You Order

The 3RA1921-1DA00 is the correct link module only when every item on this checklist is confirmed. Verify each point against the physical devices in your panel or your BOM before placing the order.

  1. Verify your contactor is 3RT Size 00 (S00) - this module only fits S00 contactors
  2. Confirm motor protector is 3RV Size 0 (S0) 3RV2.1 or 3RV2.2 model
  3. Check that contactor is 3RT2.1 or 3RT101 (compatible series)
  4. Ensure motor protector is from 3RV1.2, 3RV2.1, or 3RV2.2 lineup
  5. Verify your circuit uses AC or DC operation (module supports both)
  6. Confirm panel space allows 45 mm width, 70.3 mm depth, 42.7 mm height
  7. Check existing wiring termination is screw-based, not spring-based

If any item on this checklist cannot be confirmed, do not assume the 3RA1921-1DA00 will fit. Contact the LeadTime.ca team with your contactor and protector model numbers and we will confirm the correct link module before you order.

Frequently Asked Questions

Can the 3RA1921-1DA00 be used with a 3RT1 series contactor instead of 3RT2.1?

No. The 3RA1921-1DA00 is designed for 3RT2.1 and 3RT101 contactors. The mechanical interface and electrical contact pressure geometry of older 3RT1 series contactors differs from the 3RT2.1, and using a mismatched link module creates erratic motor operation and potential contact failure. If your contactor is a legacy 3RT1 model, contact your distributor for the correct link module part number for that series.

Does the 3RA1921-1DA00 work with both AC and DC motor control circuits?

Yes. The module supports both AC and DC operation, which is why it is suitable for a wide range of motor control configurations within the S00/S0 size class. Verify that the contactor coil and motor protector are also rated for your specific control voltage before completing the assembly.

What is the typical lead time for the 3RA1921-1DA00 when ordered from a distributor?

In-stock units ship in less than 5 business days through authorized distribution channels. For emergency maintenance situations, confirming in-stock status at the time of order is essential. LeadTime.ca ships worldwide and can confirm current availability before you commit to the order.

Is the 3RA1921-1DA00 RoHS compliant, and does it carry CE certification?

Yes to both. The 3RA1921-1DA00 is confirmed RoHS compliant and CE certified. It also carries EAC, ABS, Bureau Veritas, PRS, and RINA approvals, making it acceptable in regulated industries and international export applications without additional compliance testing at the component level.

What happens if the screw terminals in the link module are over-tightened during installation?

Excessive torque on the screw terminals can strip the internal thread or damage the terminal block, causing the electrical contact to degrade or open intermittently. If a terminal becomes damaged in this way, the entire link module should be replaced — terminal repair is not practical on this component. Use moderate hand pressure and stop tightening once the wire is fully secured.

Can one 3RA1921-1DA00 unit serve multiple contactor and protector combinations, or is it a one-to-one assembly?

The 3RA1921-1DA00 is a one-to-one interconnect — each module permanently bridges one contactor to one motor protector in a single motor starter assembly. However, the same module model is compatible across multiple contactor and protector variants within the S00/S0 size class (3RT2.1 or 3RT101 with 3RV1.2, 3RV2.1, or 3RV2.2), which simplifies inventory management for facilities running multiple machine types on the same SIRIUS platform.

Why Engineers Order From LeadTime.ca

At-a-Glance Summary

  • Part number: 3RA1921-1DA00 — electrical and mechanical link module for SIRIUS S00 contactor to S0 motor protector assemblies
  • Dimensions: 45 mm W x 70.3 mm D x 42.7 mm H; weight 0.03 kg
  • Compatible contactors: 3RT101 and 3RT2.1, Size 00 (S00) only
  • Compatible motor protectors: 3RV1.2, 3RV2.1, and 3RV2.2 in S0 and S00 sizes
  • Connection type: screw terminal, 3-pole, supports AC and DC operation
  • Certifications: CE, RoHS, EAC, ABS, Bureau Veritas, PRS, RINA
  • Country of origin: Germany
  • Single-unit price: $30.32 USD; volume pricing down to $22.74 USD at 250+ units
  • Standard in-stock lead time: under 5 business days
  • Product family: Siemens SIRIUS industrial automation control components