Siemens 3RV2021-4EA10 — 32 A CLASS 10 Motor Breaker Buying Guide

By Abdullah Zahid
12 min read
Siemens 3RV2021-4EA10 S0 motor circuit breaker 32A CLASS 10 three-pole DIN rail mount for industrial motor protection

Siemens 3RV2021-4EA10 Circuit Breaker Size S0 for Motor Protection, CLASS 10, A-Release 27–32 A, N-Release 400 A — Specifications, Wiring, and Selection Guide

When a controls engineer or panel builder is specifying motor protection for a three-phase induction motor in the 15 kW to 20 hp range, the Siemens 3RV2021-4EA10 is one of the most frequently cross-referenced SIRIUS thermal-magnetic circuit breakers on the market. This S0-size, three-pole unit provides adjustable thermal overload release from 27 to 32 A, a fixed 400 A magnetic short-circuit trip (N-release), and a rated operational voltage of 690 V — covering the full range of standard industrial supply voltages from 400 V to 690 V at 50–60 Hz. Whether you are retrofitting a failed motor starter on a pump station or building a new panel for a conveyor drive, confirming the 3RV2021-4EA10 is the correct SKU before you order is the decision this page is designed to help you make.

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

Who Should Buy the 3RV2021-4EA10 — and Who Shouldn't

The Siemens 3RV2021-4EA10 is the correct choice when all of the following apply to your application:

  • Your motor's full-load amperage (FLA) falls within the 27–32 A adjustable thermal overload release range
  • Your supply voltage is within the 400–690 V AC operational range at 50–60 Hz
  • You require CLASS 10 trip selectivity for tight coordination with upstream protection in a DOL motor starting circuit
  • Your panel layout is DIN rail–based (35 mm per DIN EN 60715) and the 45 mm S0 footprint fits your enclosure
  • Short-circuit breaking capacity of 55 kA at 400 V or 100 kA at 240 V is sufficient for your fault duty level
  • You need a thermal-magnetic base unit without auxiliary contacts, or plan to add auxiliary switch expansion later

If your motor exceeds 32 A FLA or is rated above 15 kW at 400 V, you need the 3RV2041-4PA10 (40 A, S2 size) or 3RV2061-4PA10 (63 A, S3 size). If your application requires IO-Link monitoring or predictive maintenance integration, the 3RV2741-1EA10 electronic variant is the correct selection.

On this page:

What the 3RV2021-4EA10 Actually Does in a Motor Protection Circuit

The Siemens 3RV2021-4EA10 is a fixed-installation, three-pole thermal-magnetic circuit breaker in the SIRIUS product family, designed specifically for direct-on-line (DOL) motor starter protection. Its function in a control panel is dual: the thermal overload element monitors continuous current and trips on sustained overload conditions, while the magnetic N-release element provides instantaneous trip on short-circuit faults at the fixed threshold of 400 A. These two mechanisms operate independently of control circuit power — no firmware, no auxiliary supply, no battery backup required.

The adjustable thermal release range of 27–32 A allows the installer to match the breaker to the motor's FLA directly on-site, without ordering a different variant. The CLASS 10 trip selectivity means the thermal element responds within a narrow time-current band, enabling tighter upstream coordination than CLASS 20 or CLASS 30 breakers in the same system. The base unit ships without auxiliary contacts; expansion for auxiliary switch signaling is available as a separately ordered accessory and can be added without replacing the base unit.

The 3RV2021-4EA10 is suitable for AC-3 duty cycles including S1 (continuous), S3 (intermittent with frequent starts), S4 (intermittent with frequent starts and plug braking), S5, S6, and S8 — covering the majority of industrial motor applications without requiring a higher-rated unit. At 690 V, this unit protects motors up to 30 kW; at 400 V, the rated motor power is 15 kW; at 460–480 V it corresponds to 20 hp.

Typical System Architecture for DOL Motor Starting

In a standard DOL motor starter panel, the 3RV2021-4EA10 sits between the incoming supply and the motor contactor, providing both short-circuit protection for the downstream circuit and overload protection for the motor. Here is where it fits in the signal chain:

  • Incoming three-phase supply (400–690 V, 50–60 Hz) connects to the upstream busbar or distribution board
  • The 3RV2021-4EA10 mounts on 35 mm DIN rail and receives supply at L1, L2, L3 input terminals
  • Output terminals T1, T2, T3 feed the motor contactor (or directly to soft-start / VFD input when used as upstream pre-protection)
  • The motor contactor controls switching; the 3RV2021-4EA10 handles fault interruption and overload protection
  • Optional auxiliary switch expansion connects to the PLC or control relay for remote trip status indication

Where the 3RV2021-4EA10 Gets Installed: Industries and Use Cases

Pump stations and HVAC systems are the most common deployment for this breaker. A 15 kW centrifugal pump or cooling tower fan running at 400 V with a measured FLA in the 27–32 A band is a direct match. The S3 and S4 duty cycle compatibility means the breaker handles applications with frequent starts without nuisance tripping, which is critical in water treatment and refrigeration systems with variable demand control.

In food and beverage processing, the 45 mm S0 footprint enables tight-packed multi-motor panels where conveyor drives, mixing motors, and transfer pump motors share the same enclosure. The CLASS 10 selectivity allows multiple 3RV2021-4EA10 units in the same distribution board to be coordinated with a common upstream breaker without cascading trips under single motor fault conditions.

Panel builders performing retrofit replacements of obsolete or failed motor starters in existing 400 V industrial installations choose this unit because it matches the physical DIN rail footprint and terminal type of predecessor SIRIUS variants, reducing rework time during panel modification. Its orientation-independent mounting means the retrofit can proceed regardless of how the original panel was laid out.

In soft-start and VFD pre-protection roles, the 3RV2021-4EA10 is installed upstream of the soft-start electronics to interrupt external short-circuit faults before they reach and damage the power electronics module. The 55 kA breaking capacity at 400 V provides the interrupt rating required for most industrial distribution systems in this role.

Application Typical Deployment
Industrial pump station DOL starter panel, 15 kW pump at 400 V, CLASS 10 coordination with upstream distribution board
HVAC / cooling tower fan Single S0 breaker per fan motor, S3 duty cycle, frequent start-stop on thermostat demand
Food and beverage conveyor Multi-motor panel, 3–6 units per enclosure, tightly spaced at 45 mm each, S4 duty
Soft-start pre-protection Upstream of soft-start unit, provides short-circuit interruption to protect power electronics
Retrofit of legacy DOL starter Direct DIN rail drop-in, matched terminal type and S0 footprint to predecessor unit
Water treatment / wastewater Pump motor protection in outdoor enclosure rated IP20 minimum, continuous S1 duty

Purchase-Decision Specifications at a Glance

Specification Value
Rated Continuous Current 32 A
Thermal Overload Release (Adjustable) 27–32 A
Magnetic Trip (N-Release, Fixed) 400 A
Rated Operational Voltage 690 V maximum (400 V typical industrial)
Insulation Voltage (Pollution Degree 3) 690 V AC
Short-Circuit Breaking Capacity at 240 V 100 kA
Short-Circuit Breaking Capacity at 400 V 55 kA
Operating Frequency 50–60 Hz
Trip Class CLASS 10
Size Class / Width S0 / 45 mm

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

3RV2021-4EA10 vs. Larger and Electronic Variants: Which One Do You Actually Need?

Model Rated Current Voltage Max Size Class Motor Power at 400 V Trip Type Auxiliary Contacts Best Application
3RV2021-4EA10 32 A 690 V S0 15 kW Thermal + Magnetic 0 (base unit) Up to 20 hp; space-constrained panels
3RV2041-4PA10 40 A 690 V S2 22 kW Thermal + Magnetic Optional 22–30 kW motors; larger enclosures
3RV2061-4PA10 63 A 690 V S3 45 kW Thermal + Magnetic Optional 45+ kW motors; heavy industrial
3RV2741-1EA10 32 A 690 V S0 15 kW Electronic IO-Link capable Monitoring and predictive maintenance
3RV1021-4CA10 25 A 690 V S00 11 kW Thermal + Magnetic 0 (base unit) Smaller motors; ultra-compact panels

If your motor nameplate FLA falls at 32 A and your supply is 400 V at 50–60 Hz, the 3RV2021-4EA10 is the confirmed correct choice — check current stock and pricing at LeadTime.ca.

Expert Verdict: Honest Assessment for Controls Engineers and Procurement Teams

The Siemens 3RV2021-4EA10 does three things well: it protects motors in the 27–32 A FLA range accurately with CLASS 10 selectivity, it fits a 45 mm DIN rail slot without auxiliary contact requirements, and it is one of the most widely stocked SIRIUS SKUs in industrial distribution — meaning you are unlikely to face a multi-week lead time for a standard unit. The SIRIUS family carries approximately 30–40% of the thermal-magnetic motor circuit breaker market in North America, and that market penetration translates directly into accessible spare-part availability for your installed base. For DOL motor starting in pump, fan, and conveyor applications up to 15 kW at 400 V or 20 hp at 460–480 V, this is a well-proven and cost-effective choice.

Where the 3RV2021-4EA10 has real limits: if your motor FLA is below 27 A, you cannot use this unit safely — setting the thermal release above actual motor FLA leaves the motor under-protected between the FLA and 27 A. If your motor exceeds 32 A FLA or 15 kW at 400 V, this unit will cause nuisance trips under normal loaded running conditions. For applications requiring current monitoring, IO-Link reporting to a PLC, or integration into a predictive maintenance scheme, the 3RV2741-1EA10 electronic variant is the correct selection, though it typically requires 2–4 weeks delivery compared to the 1–5 business day availability typical for the 3RV2021-4EA10. And when soft-start or VFD integration is the primary goal, the 3RV2021-4EA10 plays only an upstream pre-protection role — it is not a soft-starter and does not limit motor inrush.

From a procurement standpoint, the 3RV2021-4EA10 is a high-volume SKU that most major global distributors hold on the shelf. Lead times of 1–5 business days are typical for standard orders. If you are an OEM panel builder with recurring volume, LeadTime.ca can accommodate volume pricing discussions. If you are in a production-critical emergency replacement situation, the fast lead time on this unit is a genuine advantage over electronic or large-frame alternatives. 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.

Wiring and Installation Overview

  • Mount the 3RV2021-4EA10 on a 35 mm DIN rail per DIN EN 60715 using the snap-on clip and screw fastener; mounting position is orientation-independent
  • Connect three-phase supply conductors to input terminals L1, L2, L3 and motor load wires to output terminals T1, T2, T3 using M3 screw terminals rated for 1.5–2.5 mm² wire
  • Maintain minimum 30 mm vertical spacing between live parts at 400 V; increase to 50 mm minimum vertical spacing at 690 V
  • Horizontal spacing between live parts: 9 mm minimum at 400 V, 30 mm minimum at 690 V — do not over-crowd adjacent live components
  • Confirm all conductors are fully seated and secured before energizing; do not attempt wiring with supply energized

Commissioning Overview: Setting the Thermal Release and Verifying Trip Function

  • Obtain motor nameplate FLA and set the thermal overload release knob to match the FLA within the 27–32 A range before energizing
  • Energize the motor and allow it to reach rated speed; confirm the thermal release does not trip during normal acceleration — if it does, verify the thermal setting matches actual FLA using a clamp meter at each pole
  • After the motor reaches stable running current, verify current draw does not exceed the thermal setting by more than 10%
  • Perform a manual trip test: push the trip lever to the full down position and verify it latches; reset by pushing fully up and confirm the lever holds before returning to service
  • Document the final thermal release setting and commissioning results in the panel as-built diagram and maintenance log

Wrong-Part Prevention Checklist Before You Order

Confirm every item below before placing your order. These checks prevent the most common ordering errors on this part number:

  1. Verify three-pole configuration matches your three-phase motor supply (this is 3-pole, not 1-pole or 2-pole)
  2. Confirm 32 A setting aligns with your motor's full-load amperage and thermal class requirement
  3. Check operating voltage: 690 V max means do not exceed 690 V AC supply; 400 V rated is common North American industrial standard
  4. Ensure 50-60 Hz compatibility for your region (this unit rated 50-60 Hz)
  5. Confirm screw terminal connection type matches your panel wiring gauge (M3 screw terminals for 1.5-2.5 mm² wire)
  6. Verify magnetic N-release setting is 400 A and acceptable for your short-circuit duty
  7. Do not confuse with S00 size (smaller) or S2, S3 (larger) variants
  8. Confirm auxiliary switch expansion capability is not needed before ordering base unit

If any item above does not match your application, contact the LeadTime.ca team to confirm the correct variant before ordering — or return to the product page to review available SIRIUS options.

Frequently Asked Questions

Can the 3RV2021-4EA10 be used upstream of a soft-start or VFD, or does it need to be replaced with a different protection type?

Yes, the 3RV2021-4EA10 can be used as a pre-protection circuit breaker upstream of a soft-start unit or VFD. In this role, it provides short-circuit interruption to protect the power electronics from external faults. The 55 kA breaking capacity at 400 V is sufficient for most industrial distribution systems in this application. Note that the 3RV2021-4EA10 does not perform motor current monitoring in a VFD-driven circuit — the VFD's own overload protection handles that function.

What happens if my motor FLA is 25 A — can I still use the 3RV2021-4EA10 and set it to the minimum 27 A?

No. If your motor FLA is below 27 A, this unit is not the correct choice. Setting the thermal release to 27 A when motor FLA is 25 A means the breaker will not trip on overloads between 25 A and 27 A, leaving the motor under-protected in that range. For motors with FLA below 27 A, select a smaller model — the 3RV1021-4CA10 at 25 A (S00 size) or another appropriately rated variant.

What is CLASS 10 selectivity and how does it affect upstream protection coordination?

CLASS 10 defines a narrow trip time band on the time-current curve: the thermal element must trip within 10 seconds at 7.2 times the set current. This narrow band enables tighter coordination with upstream fuses or main circuit breakers, reducing the risk of cascading trips across multiple motor circuits during a single fault event. CLASS 20 and CLASS 30 breakers have wider trip bands, which can be advantageous for high-inertia motors with long acceleration times but reduce selectivity in multi-motor panels.

Does the 3RV2021-4EA10 include auxiliary contacts for PLC fault signaling?

The base unit ships without auxiliary contacts. Auxiliary switch expansion is available as a separately ordered accessory that can be added to the base unit without replacing it. If your application requires remote trip status indication to a PLC or control relay, confirm the auxiliary switch part number before committing to the base unit order — or contact LeadTime.ca to discuss the complete accessory package.

What is the ambient temperature operating range, and is the 3RV2021-4EA10 suitable for outdoor enclosures in variable climates?

The 3RV2021-4EA10 is rated for ambient operating temperatures from -20°C to +60°C. The IP20 protection class means it is not suitable for outdoor installations without a protective enclosure — it requires a rated panel or cabinet to protect against moisture, conductive dust, and direct environmental exposure. For outdoor pump stations or field panels, the enclosure must provide the environmental protection; the breaker itself provides pollution degree 3 insulation rating for industrial indoor environments.

How does the 3RV2021-4EA10 compare on lead time versus the electronic 3RV2741-1EA10?

The 3RV2021-4EA10 is a high-volume SKU with standard stock at most major global distributors; typical delivery is 1–5 business days for in-stock orders. The 3RV2741-1EA10 electronic variant typically requires 2–4 weeks due to lower stock volumes and more complex supply chain handling. For unplanned motor failures requiring rapid replacement, the thermal-magnetic 3RV2021-4EA10 is the faster procurement option.

Why Order the 3RV2021-4EA10 from LeadTime.ca

  • Ships worldwide — no geographic restrictions on order origin or delivery destination
  • Access to hard-to-source SIRIUS variants including accessory and expansion modules for base units
  • Volume pricing available for OEM panel builders and recurring procurement programs
  • Fast response for lead time confirmation before you commit to a build schedule
  • Knowledgeable distributor team familiar with SIRIUS motor protection product selection for retrofit and new build applications

At-a-Glance Summary

  • Siemens 3RV2021-4EA10: S0 size, three-pole thermal-magnetic circuit breaker, 32 A rated, CLASS 10 trip selectivity
  • Thermal overload release adjustable from 27 to 32 A; magnetic N-release fixed at 400 A
  • Rated operational voltage 690 V maximum; 400 V typical North American industrial supply; 50–60 Hz
  • Short-circuit breaking capacity: 100 kA at 240 V, 55 kA at 400 V, 10 kA at 500 V, 4 kA at 690 V
  • Motor power ratings: 15 kW at 400 V, 20 hp at 460–480 V, 30 kW at 690 V (AC-3 duty)
  • Physical footprint: 45 mm wide (S0), 97 mm height, 35 mm DIN rail mounting, orientation-independent
  • Ambient operating temperature: -20°C to +60°C; IP20 protection class
  • Shock resistance: 25 g / 11 ms per IEC 60068-2-27; insulation voltage 690 V AC at pollution degree 3
  • Base unit ships without auxiliary contacts; auxiliary switch expansion available as separately ordered accessory
  • Typical in-stock lead time: 1–5 business days at major global distributors